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PROJECT DOCUMENT OF PERVIOUS CONCRETE

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This document is prepared for our major project submission for B.tech degree. the project deals with improvement of compressive strength of pervious concrete with out affecting its permeability property much.

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PROJECT DOCUMENT OF PERVIOUS CONCRETE

  1. 1. A PROJECT REPORT ON “IMPROVEMENT OF COMPRESSIVE STRENGTH OF PERVIOUS CONCRETE” Submitted in partial fulfilment of the requirements for the award of the Degree of BACHELOR OF TECHNOLOGY IN CIVIL ENGINEERING Submitted by G.AJITH KUMAR (13711A0122) B.S.V. DINESH (13711A0103) G.VAMSI KRISHNA (13711A0120) K.TEJA SREENIVAS (13711A0129) K.VINAY KUMAR (13711A0131) Under the esteemed Guidance of Mr. SK.FAYAZ M.tech Department of Civil Engineering DEPARTMENT OF CIVIL ENGINEERING NARAYANA ENGINEERING COLLEGE [An ISO 9001:2008 Certified] [Recognized by A.I.C.T.E., Affiliated to J.N.T.U., Anantapur] NELLORE, Nellore-524 001(A.P.), India 2013-2017 NARAYANAENGINEERINGCOLLEGE::NELLORE
  2. 2. [Recognized by A.I.C.T.E., Affiliated to J.N.T.U., Anantapur] DEPARTMENT OF CIVIL ENGINEERING CERTIFICATE The is to certify that the project report entitled “IMPROVEMENT OF COMPRESSIVE STRENGTH OF PERVIOUS CONCRETE " being submitted by G.AJITH KUMAR (13711A0122) B.S.V. DINESH (13711A0103) G.VAMSI KRISHNA (13711A0120) K.TEJA SREENIVAS (13711A0129) K.VINAY KUMAR (13711A0131) In partial fulfilment of the requirements for the award of degree of BACHELOR OF TECHNOLOGY IN CIVIL ENGINEERING of Jawaharlal Nehru Technical University, Anantapur is a bonafied work carried out by them under my guidance and supervision during the academic year 2013-2017. The results presented in this project have not been submitted to any other university or institute for the award of any degree or diploma. Mr. SK.FAYAZ.M.Tech Dr. K.YUGANDHAR REDDYM.Tech,Ph.D Assistant Professor HEAD OF THE DEPARTMENT Department of Civil Engineering Department of Civil Engineering Narayana Engineering College Narayana Engineering College Nellore Nellore Date of Viva-Voice: 24-04-2017 INTERNAL EXAMINER EXTERNAL EXAMINER ACKNOWLEDGEMENT We would like express our deep sense of gratitude to our project guide Mr.Sk.FAYAZ, Assistant professor, Department of civil engineering, who has guided
  3. 3. our work with scholarly advice and meticulous care. He had shown keen interest and personal care at every stage of our project. We are profoundly thankful to Project Coordinator Mr. Sk.RASHID, Assistant professor, Department of civil engineering for his moral support and to Prof.K.YUGANDHAR REDDYM.Tech,Ph.D, Professor & Head of the Department of civil engineering, for his cooperation and encouragement. We wish to express our sincere thanks to Dr. B.V.RAMANA REDDY, Principal for his kind gesture and support. We are indebted to the Management of Narayana engineering college, Nellore for providing the necessary infrastructure and good academic environment in an endeavour to complete the project. We are extremely grateful to Dr. P.NARAYANAPh.D., Chairman, Narayana Educational Institutions, Andhra Pradesh for his good blessings. We are thankful to the lab technicians of Department of Civil Engineering for their co-operation during the project. Finally, we like to thank our parents, friends and the people who directly and indirectly helped us for the successful completion of project. Project Associates G.AJITH KUMAR (13711A0122) B.S.V. DINESH (13711A0103) G.VAMSI KRISHNA (13711A0120) K.TEJA SREENIVAS (13711A0129) K.VINAY KUMAR (13711A0131)
  4. 4. ABSTRACT Pervious concrete is a special type of concrete, which consists of cement, coarse aggregates, water and if required, admixtures and other cementitious materials. As there are no fine aggregates used in the concrete matrix, the void content is more which allows the water to flow through its body. So the pervious concrete is also called as Permeable concrete and Porous concrete. There is lot of research work is going in the field of pervious concrete. The compressive strength of pervious concrete is less when compared to the conventional concrete due to its porosity and voids. Hence, the usage of pervious concrete is limited even though it has lot of advantages. If the compressive strength and flexural strength of pervious concrete is increased, then it can be used for more number of applications. For now, the usage of pervious concrete is mostly limited to light traffic roads only. If the properties are improved, then it can also be used for medium and heavy traffic rigid pavements also. Along with that, the pervious concrete eliminates surface runoff of storm water, facilitates the ground water recharge and makes the effective usage of available land. The main aim of our project is to improve the strength characteristics of pervious concrete. But it can be noted that with increase in strength, the permeability of pervious concrete will be reduced. Hence, the improvement of strength should not affect the permeability property because it is the property which serves its purpose.
  5. 5. 5 Chapter-1 INTRODUCTION 1.1 Introduction: Pervious concrete which is also known as the no-fines, porous, gap-graded, and permeable concrete and Enhance porosity concrete have been found to be a reliable storm water management tool. By definition, pervious concrete is a mixture of gravel or granite stone, cement, water, little to no sand (fine aggregate). When pervious concrete is used for paving, the open cell structures allow storm water to filter through the pavement and into the underlying soils. In other words, pervious concrete helps in protecting the surface of the pavement and its environment. As stated above, pervious concrete has the same basic constituents as conventional concrete, 15 -30% of its volume consists of interconnected void network, which allows water to pass through the concrete. Pervious concrete can allow the passage of 11.35-18.97 liters of water per minute through its open cells for each square foot (0.0929m2) of surface area which is far greater than most rain occurrences. Apart from being used to eliminate or reduce the need for expensive retention ponds, developers and other private companies are also using it to free up valuable real estate for development, while still providing a paved park. Pervious concrete is also a unique and effective means to address important environmental issues and sustainable growth. When it rains, pervious concrete automatically acts as a drainage system, thereby putting water back where it belongs. Pervious concrete is rough textured, and has a honeycombed surface, with moderate amount of surface ravelling which occurs on heavily travelled roadways. Carefully controlled amount of water and cementitious materials are used to create a paste. The paste then forms a thick coating around aggregate particles, to prevent the flowing off of the paste during mixing and placing. Using enough paste to coat the particles maintain a system of interconnected voids which allow water and air to pass through. The lack of sand in pervious concrete results in a very harsh mix that negatively affects mixing, delivery and placement. Also, due to the high void content, pervious concrete is light in weight (about 1600 to 2000 kg/m3). Pervious concrete
  6. 6. 6 void structure provides pollutant captures which also add significant structural strength as well. It also results in a very high permeable concrete that drains quickly. Pervious concrete can be used in a wide range of applications, although its primary use is in pavements which are in: residential roads, alleys and driveways, low volume pavements, low water crossings, sidewalks and pathways, parking areas, tennis courts, slope stabilisation, sub-base for conventional concrete pavements etc., Figure1.1: pervious concrete cube blocks
  7. 7. 7 Figure1.2: Pervious concrete beam Pervious concrete system has advantages over impervious concrete in that it is effective in managing run-off from paved surfaces, prevent contamination in run-off water, and recharge aquifer, repelling salt water intrusion, control pollution in water seepage to ground water recharge thus, preventing subterranean storm water sewer drains, absorbs less heat than regular concrete and asphalt, reduces the need for air conditioning. Pervious concrete allows for increased site optimization because in most cases, its use should totally limit the need for detention and retention ponds, swales and other more traditional storm water management devices that are otherwise required for compliances with the Federal storm water regulations on commercial sites of one acre or more. By using pervious concrete, the ambient air temperature will be reduced, requiring less power to cool the building. In addition, costly storm water structures such as piping, inlets and ponds will be eliminated. Construction scheduling will also be improved as the stone recharge bed will be installed at the beginning of construction, enhancing erosion control measures and preventing rain delays due to harsh site conditions. Apparently, when compared to conventional concrete, pervious concrete has a lower compressive strength, greater permeability, and a lower unit weight (approximately 70% of conventional concrete). However, pervious concrete has a greater advantage in many regards. Nevertheless, it has its own limitations which must be put in effective consideration when planning its use. Structurally when higher permeability and low strength are required, the effect of variation in aggregate size on strength and permeability for the same aggregate cement ratio need to be investigated.
  8. 8. 8 Figur1.3: water flowing through pervious concrete cube 1.2 Brief History: Pervious Concrete has been around for hundreds of years. The Europeans recognized the insulating properties in structural pervious concrete for their buildings. Europeans have also used pervious concrete for paving. Stories passed down through the years tell us that soldiers didn’t mind walking on pervious roads during World War II because it meant their feet would be dry. Pervious was brought to the United States after World War II. It first showed up in Florida and other southern coastal states. Slowly it has migrated to the other states where it has met different successes. As with any new product, it has had to prove itself. Many well intended ready mix producers have produced the product and many well intended contractors have placed the product. Some did well, others did not. As it is true with any material and construction technique, there is a science to it and a best way to conduct the construction. Education and experience is the key to success. The coastal states have experienced pervious concrete for over 20 years. The hesitation to move into the Midwest and Northern States was mainly due to freeze/thaw concerns. Now that those concerns are no longer considered a problem, the product has moved quickly across the United States. In the 1990’s the U.S. Environmental Protection Administration (EPA) came out with the Clean Water Act (CWA), that later led to other phases of implementation to preserve the waterways from stormwater borne pollutants. EPA identifies “stormwater runoff is generated when precipitation from rain and snowmelt events flow over land or impervious surfaces and does not percolate into the ground. As the runoff flows over the land or impervious surfaces (paved streets, parking lots, and building rooftops), it accumulates debris, chemicals, sediment or other pollutants that could adversely affect water quality if the runoff is discharged untreated. The primary method to control stormwater discharges is the use of best management practices (BMPs).” (EPA.gov). Pervious concrete is one of many BMP’s recognized by the EPA as well as our local American Public Works Association (APWA) and the Mid America Regional Council (MARC). Basically, it requires the developer/owner to keep as much stormwater on property as possible. If stormwater leaves the property it must leave cleaner and cooler than before. Pervious concrete allows for the filtering/cleaning and detainment of stormwater.
  9. 9. 9 1.3 General Properties of Pervious Concrete: The plastic pervious concrete mixture is stiff compared to traditional concrete. Slumps, when measured, are generally less than 20mm, although slumps as high as 50mm have been used. However, slump of pervious concrete has no correlation with its workability and hence should not be specified as an acceptance criterion. Typical densities and void contents are on the order of 1600 kg/m3 to 2000 kg/m3 and 20 to 25% respectively. The infiltration rate (permeability) of pervious concrete will vary with aggregate size and density of the mixture, but will fall into the range of 80 to 720 litres per minute per square meter. A moderate porosity pervious concrete pavement system will typically have a permeability of 143 litres per minute per square meter. Perhaps nowhere in the world would one see such a heavy rainfall. In contrast the steady state infiltration rate of soil ranges from 25 mm/hr to 0.25 mm/hr. This clearly suggests that unless the pervious concrete is severely clogged up due to possibly poor maintenance it is unlikely that the permeability of pervious concrete is the controlling factor in estimating runoff (if any) from a pervious concrete pavement. For a given rainfall intensity the amount of runoff from a pervious concrete pavement system is controlled by the soil infiltration rate and the amount of water storage available in the pervious concrete and aggregate base (if any) under the pervious concrete. Generally for a given mixture proportion strength and permeability of pervious concrete are a function of the concrete density. Greater the amount of consolidation higher the strength, and lower the permeability. Since it is not possible to duplicate the in-place consolidation levels in a pervious concrete pavement one has to be cautious in interpreting the properties of pervious concrete specimens prepared in the laboratory. Such specimens may be adequate for quality assurance namely to ensure that the supplied concrete meets specifications. Core testing is recommended for knowing the in-place properties of the pervious concrete pavement. The relationship between the w/cm and compressive strength of conventional concrete is not significant. A high w/cm can result in the paste flowing from the aggregate and filling the void structure. A low w/cm can result in reduced adhesion between aggregate particles and placement problems. Flexural strength in pervious concretes generally ranges between about 1 MPa and 3.8 MPa. Numerous successful projects have been successfully executed and have lasted several winters in harsh Northern climates. This is possibly because pervious concrete is unlikely to remain saturated in the field.
  10. 10. 10 The freeze thaw resistance of pervious concrete can be enhanced by the following measures 1. Use of fine aggregates to increase strength and slightly reduce voids content to about 20%. 2. Use of air-entrainment of the paste. 3. Use of a perforated PVC pipe in the aggregate base to capture all the water and let it drain away below the pavement. Abrasion and ravelling could be a problem. Good curing practices and appropriate w/cm (not too low) is important to reduce ravelling. Where as severe ravelling is unacceptable some loose stones on a finished pavement is always expected. Use of snow ploughs could increase ravelling. A plastic or rubber shield at the base of the plough blade may help to prevent damage to the pavement. 1.4 Benefits of Pervious Concrete: Pervious concrete pavement systems provide a valuable stormwater management tool under the requirements of the EPA Storm Water Phase II Final Rule Phase II regulations provide programs and practices to help control the amount of contaminants in our waterways. Impervious pavement particularly parking lots collect oil, anti-freeze, and other automobile fluids that can be washed into streams, lakes, and oceans when it rains. EPA Storm Water regulations set limits on the levels of pollution in our streams and lakes. To meet these regulations, local officials have considered two basic approaches. They are 1) Reduce the overall runoff from an area 2) Reduce the level of pollution contained in runoff Efforts to reduce runoff include zoning ordinances and regulations that reduce the amount of impervious surfaces in new developments (including parking and roof areas), increased green space requirements, and implementation of “stormwater utility districts” that levy an impact fee on a property owner based on the amount of impervious area. Efforts to reduce the level of pollution from stormwater include requirements for developers to provide systems that collect the “first flush” of rainfall, usually about 25 mm, and “treat” the pollution prior to release. Pervious concrete pavement reduces or eliminates runoff and permits “treatment” of pollution: two studies conducted on the long-term pollutant removal in porous pavements suggest high pollutant removal rates. By capturing the first flush of rainfall and allowing it to percolate into the ground, soil chemistry and biology are allowed to “treat” the polluted water naturally. Thus, stormwater retention areas may be reduced or eliminated, allowing increased
  11. 11. 11 land use. Furthermore, by collecting rainfall and allowing it to infiltrate, groundwater and aquifer recharge is increased, peak water flow through drainage channels is reduced and flooding is minimized. In fact, the EPA named pervious pavements as a BMP for stormwater pollution prevention (EPA 1999) because they allow fluids to percolate into the soil. Another important factor leading to renewed interest in pervious concrete is an increasing emphasis on sustainable construction. Because of its benefits in controlling stormwater runoff and pollution prevention, pervious concrete has the potential to help earn a credit point in the U.S. Green Building Council’s Leadership in Energy & Environmental Design (LEED) Green Building Rating System, increasing the chance to obtain LEED project certification. This credit is in addition to other LEED credits that may be earned through the use of concrete for its other environmental benefits, such as reducing heat island effects recycled content and regional materials. The light colour of concrete pavements absorbs less heat from solar radiation than darker pavements, and the relatively open pore structure of pervious concrete stores less heat, helping to lower heat island effects in urban areas. Trees planted in parking lots and city sidewalks offer shade and produce a cooling effect in the area, further reducing heat island effects. Pervious concrete pavement is ideal for protecting trees in a paved environment. (Many plants have difficulty growing in areas covered by impervious pavements, sidewalks and landscaping, because air and water have difficulty getting to the roots.) Pervious concrete pavements or sidewalks allow adjacent trees to receive more air and water and still permit full use of the pavement pervious concrete provides a solution for landscapers and architects who wish to use greenery in parking lots and paved urban areas. Although high-traffic pavements are not a typical use for pervious concrete, concrete surfaces also can improve safety during rainstorms by eliminating ponding (and glare at night), spraying, and risk of hydroplaning.
  12. 12. 12 1.5 Major applications of pervious concrete:  Low-volume pavements  Residential roads, alleys, and driveways  Sidewalks and pathways  Parking areas  Low water crossings  Tennis courts  Sub base for conventional concrete pavements  Slope stabilization  Well linings  Hydraulic structures  Swimming pool decks  Pavement edge drains and Tree grates in sidewalks  Groins and seawalls  Noise barriers  Walls (including load-bearing)
  13. 13. 13 Chapter-2 LITERATURE REVIEW 2.1 Background: Portland cement pervious concrete (PCPC) has great potential to reduce roadway noise, improve splash and spray, and improve friction as a surface wearing course. A pervious concrete mix design for a surface wearing course must meet the criteria of adequate strength and durability under site-specific loading and environmental conditions. To date, two key issues that have impeded the use of pervious concrete in the United States are that strengths of pervious concrete have been lower than necessary for required applications and the freeze-thaw durability of pervious concrete has been suspect. A research project on the freeze-thaw durability of pervious concrete mix designs at Iowa State University (ISU) has recently been completed (Schaefer et al. 2006). The results of this study have shown that a strong, durable pervious concrete mix design that will withstand wet, hard- freeze environments is possible. The strength is achieved through the use of a small amount of fine aggregate (i.e., concrete sand) and/or latex admixture to enhance the particle-to-particle bond in the mix. The preliminary results were reported in Kevern et al. (2005). The recent work has been limited to laboratory testing and to only a few mixes using two sources of aggregates. Preliminary laboratory testing has shown the importance of compaction energy on the properties and performance of the mixes, an issue that has direct bearing on the construction technique used to place the materials in the field. Tests conducted in Purdue University’s Tire-Pavement Test Apparatus showed reduced noise levels above 1,000 hertz (Hz) and some increase in noise levels below 1,000 Hz. The increased porosity of pervious concrete increased mechanical excitation and interaction between the tire and pavement at frequencies below about 1,000 Hz and at frequencies above about 1,000 Hz; the air pumping mechanics that dominate at such frequencies are relieved by the increased porosity leading to decreased high-frequency noise levels. A recent European Scan (sponsored by the Federal Highway Administration/FHWA) indicated that the use of pervious pavements as friction courses is declining, due to the European preference toward an exposed aggregate concrete. Also, clogging, ravelling, and winter maintenance were indicated as problem areas. Participants in the Scan felt that the use of pervious concrete was not given enough time to develop into a viable paving alternative.
  14. 14. 14 The American experience with pervious concrete is limited. It is important to ascertain what material elements can be included in the pervious mix design to address the ravelling and clogging issues. If winter maintenance elements and concerns cannot be overcome, pervious concrete may be able to be used in warm weather regions The National Concrete Pavement Technology Centre (National CP Tech Centre) at ISU developed a research project titled “An Integrated Study of Portland Cement Pervious Concrete for Wearing Course Applications.” The objective of the research was to conduct a comprehensive study focused on the development of pervious concrete mix designs having adequate strength and durability for wearing course pavements and having surface characteristics that reduce noise and enhance skid resistance while providing adequate removal of water from the pavement surface and structure. A range of mix designs was used necessary to meet requirements for wearing course applications. Further, constructability issues for wearing course sections were addressed to ensure that competitive and economical placement of the pervious concrete can be done in the field. The focus of the National CP Tech Centre’s work on pervious concrete was the development of a durable wearing course that can be used in highway applications for critical noise, splash/spray, skid resistance, and environmental concerns. The comprehensive study is anticipated to be conducted over a five- year period and is further described below. 2.2 Strength development of pervious concrete: A recent National CP Tech Centre report titled Mix Design Development for Pervious Concrete in Cold Weather Climates (Schaefer et al. 2006) provides a summary of the available literature concerning the construction materials, material properties, surface characteristics, pervious pavement design, construction, maintenance, and environmental issues for PCPC. The primary goal of the research conducted was to develop a pervious concrete that would provide freeze- thaw resistance while maintaining adequate strength and permeability for pavement applications. The key findings from the literature review can be summarized as follows: The engineering properties reported in the literature from the United States indicate a high void ratio, low strength, and limited freeze-thaw test results. It is believed that these reasons have hindered the use of pervious concrete in the hard wet freeze regions (i.e., Midwest and Northeast United States). The typical mix design of pervious concrete used in the United States consists of cement, single-sized coarse aggregate (i.e., between 25mm and 100mm),
  15. 15. 15 and water to cement ratio ranging from 0.27 to 0.43. The 28-day compressive strength of pervious concrete ranges from 5 to 20 MPa, with a void ratio ranging from 14% to 31% and a permeability ranging from 0.025 to 0.6 cm/sec. The advantages of pervious concrete include improving skid resistance by removing water that creates splash and spray during precipitation events, reducing noise, minimizing heat islands in large cities, preserving native ecosystems, and minimizing cost in some cases. Surface coarse pervious concrete pavement systems have been reported to be used in Europe and Japan. Studies have shown that pervious concrete generally produces a quieter than normal concrete with noise levels ranging from 3% to 10% lower than those of normal concrete. The research conducted at ISU included studies of the materials used in the pervious concrete, the mix proportions and specimen preparation, the resulting strength and permeability, and the effects of freeze-thaw cycling. A variety of aggregate sizes was tested and both limestone aggregates and river run gravels were used. The key parameters investigated were strength, permeability, and freeze-thaw resistance. It can be seen that as the void ratio increases, the strength decreases but the permeability increases. Shown in the figure is a target range of void ratio between 15% and 19% in which the strength and permeability are sufficient for the intended purpose. Subsequent freeze-thaw tests showed that a durable mix can be developed is Key to the development of a mix that would provide sufficient strength, adequate permeability, and freeze-thaw resistance was the addition of a small amount of sand, about 5% to 7%, that increased the bonding of the paste to the aggregates. The laboratory studies also raised the issue of compaction energy on the results. The difference between the compaction energies related to the amplitude of the vibrating pan, while the frequency was constant. The results of comparisons of two compaction energies used in the laboratory, and it can be seen that higher compaction energy results in stronger mixes at given void ratios. These results point to the importance of proper compaction in the field. A number of field sites have also been investigated and the results are reported in the master’s thesis by Kevern (2006). Samples from a Sioux City, Iowa site showed more uniform compaction in the top 150mm, with low compaction causing high voids and low strength in the bottom layer. A mix proposed for a site in North Liberty, Iowa showed that limestone mixes with unit weight less than 2000kg/m3 can be freeze-thaw resistant.
  16. 16. 16 Chapter-3 EXPERIMENTAL WORK 3.1 MATERIALS USED: 3.1.1 CEMENT: Cement is a key to infrastructure industry and is used for various purposes and also made in many compositions for a wide variety of uses. Cements may be named after the principal constituents, after the intended purpose, after the object to which they are applied or after their characteristic property. Cement used in construction are sometimes named after their commonly reported place of origin, such as Roman cement, or for their resemblance to other materials, such as Portland cement, which produces a concrete resembling the Portland stone used for building in Britain. The term cement is derived from the Latin word Caementum, which is meant stone chippings such as used in Roman mortar not-the binding material itself. Cement, in the general sense of the word, described as a material with adhesive and cohesive properties, which make it capable of bonding mineral fragments in to a compact whole. The first step of reintroduction of cement after decline of the Roman Empire was in about 1790, when an Englishman, J.Smeaton, found that when lime containing a certain amount of clay was burnt, it would set under water. This cement resembled that which had been made by the Romans. Further investigations by J. Parker in the same decade led to the commercial production of natural hydraulic cement. Table 3.1: Typical composition of ordinary Portland cement Name of compound Chemical Composition Abbreviation Tricalcium Silicate 3CaO.SiO2 C3S Dicalcium Silicate 2CaO.SiO2 C2S Tricalcium aluminate 3CaO.Al2O3 C3A Tetracalcium alumino ferrite 4CaO.Al2O3.Fe2O3 C4AF
  17. 17. 17 Figure3.1: Ordinary Portland cement These compounds interact with one another in the kiln to form a series of more complex products. Portland cement is varied in type by changing the relative proportions of its four predominant chemical compounds and by the degree of fineness of the clinker grinding. A small variation in the composition or proportion of its raw materials leads to a large variation in compound composition Calculation of the potential composition of Portland cement is generally based on the Bogue composition (R.H Bogue). In addition to the main compounds, there exist minor compounds such as MgO, TiO2, K2O and Na2O; they usually amount to not more than a few percent of the mass of the cement. Two of the minor compounds are of particular interest: the oxides of sodium and potassium known as the alkalis. They have been found to react with some aggregates, the products of the reaction causing disintegration of the concrete and have also observed to affect the rate of gain of strength of cement. Present knowledge of cement chemistry indicates that the major cement compounds have the following properties.  Tricalcium Silicate, C3S hardens rapidly and is largely responsible for initial set and early strength development. The early strength of Portland cement concrete is higher with increased percentages of C3S.  Dicalcium Silicate, C2S hardens slowly and contributes largely to strength increase at ages beyond one week.
  18. 18. 18  Tricalcium aluminate, C3A liberates a large amount of heat during the first days of hardening. It also contributes slightly for early strength development. Cements with low percentages of this compound are especially resistant to soils and waters containing sulphates. Concrete made of Portland cement with C3A contents as high as 10.0%, and sometimes greater, has shown satisfactory durability, provided the permeability of the concrete is low.  Tetracalcium Alumina ferrite, C4AF reduces the clinkering temperature. It will act as a flux in burning the clinker. It hydrates rather rapidly but contributes very little to strength development. Most colour effects are due to C4AF series and its hydrates. The compounds Tricalcium aluminate and Tricalcium silicate develop the greatest heat, then follows Tetracalcium alumino ferrite, with dicalcium silicate developing the least heat of all. In our project work, we have used Ordinary Portland Cement (OPC) of grade 53. It is a higher strength cement to meet the needs of the consumer for higher strength concrete. As per BIS requirements the minimum 28 days compressive strength of 53 Grade OPC should not be less than 53 MPa. For certain specialised works, such as pre stressed concrete and certain items of precast concrete requiring consistently high strength concrete, the use of 53 grade OPC is found very useful. 53 grade OPC produces higher-grade concrete at very economical cement content. In concrete mix design, for concrete M-20 and above grades a saving of 8 to 10 % of cement may be achieved with the use of 53 grade OPC. Ordinary Portland Cement (OPC) 53 Grade should surpass the requirements of IS: 12269-1987 Grade. It is produced by inter grinding of high grade clinker (with high C3S content) and right quality gypsum in predetermined proportions. It is recognized for its high early strength and excellent ultimate strength because of its optimum particle size distribution, superior crystalline structure and balanced phase composition and hence widely used and suitable for speedy construction, durable concrete and economic concrete mix designs.
  19. 19. 19 3.1.1.1 Advantages:  Superior quality ensures substantial savings in cement consumption  Development of very high compressive strength in early stages helps in early de- shuttering  Superior resistance to sulphate attack due to less C3A content  Durable Concrete  Feasible for economical concrete mix designs  Low percentage of alkalies, chlorides, magnesia and free lime results in longer life of concrete structures. 3.1.2 AGGREGATES: 3.1.2.1 Coarse aggregates: Aggregates were first considered to simply be filler for concrete to reduce the amount of cement required. However, it is now known that the type of aggregate used for concrete can have considerable effects on the plastic and hardened state properties of concrete. They can form 80% of the concrete mix so their properties are crucial to the properties of concrete. Aggregates can be broadly classified into four different categories: these are heavyweight, normal weight, lightweight and ultra-lightweight aggregates. However in most concrete practices only normal weight and lightweight aggregates are used. The other types of aggregates are for specialist uses, such as nuclear radiation shielding provided by heavyweight concrete and thermal insulation using lightweight concrete. 3.1.2.1.1 Classification of aggregates: The alternative used in the manufacture of good quality concrete, is to obtain the aggregate in at least two size groups, i.e.:  Fine aggregate often called sand which are less than 4.75mm in size.  Coarse aggregate, which comprises material greater than 4.75mm in size.
  20. 20. 20 On the other hand, there are some properties possessed by the aggregate but absent in the parent rock: particle shape and size, surface texture, and absorption. All these properties have a considerable influence on the quality of the concrete, either in fresh or in the hardened state. It has been found that aggregate may appear to be unsatisfactory on some count but no trouble need be experienced when it is used in concrete 3.1.2.1.2 Aggregate properties: By selecting different sizes and types of aggregates and different ratios of aggregate to cement ratios, a wide range of concrete can be produced economically to suit different requirements. Important properties of an aggregate which affect the performance of a concrete are discussed as follows: Figure3.2: 20mm coarse aggregates 3.1.2.1.3 Sampling: Samples shall be representative and certain precautions in sampling have to be made. No detailed procedures can be laid down as the conditions and situations involved in taking samples in the field can vary widely from case to case. Nevertheless, a user can obtain reliable results bearing in mind that the sample taken is to be representative of the bulk of the material. The main sample shall be made up of portions drawn from different parts of the whole. In the case of stockpiles, the sample obtained is variable or segregated, a large number of increments should be taken and a larger sample should be dispatched for testing.
  21. 21. 21 3.1.2.1.4 Particle shape and texture: Roundness measures the relative sharpness or angularity of the edges and corners of a particle. Roundness is controlled largely by the strength and abrasion resistance of the parent rock and by the amount of wear to which the particle has been subjected. In the case of crushed aggregate, the particle shape depends not only on the nature of the parent rock but also on the type of crusher and its reduction ratio, i.e. the ratio of the size of material fed into the crusher to the size of the finished product. Particles with a high ratio of surface area to volume are also of particular interest for a given workability of the control mix. Elongated and flaky particles are departed from equi-dimensional shape of particles and have a larger surface area and pack in an isotropic manner. Flaky particles affect the durability of concrete, as the particles tend to be oriented in one plane, with bleeding water and air voids forming underneath. The flakiness and elongation tests are useful for general assessment of aggregate but they do not adequately describe the particle shape. The presence of elongated particles in excess of 10 to 15% of the mass of coarse aggregate is generally undesirable, but no recognized limits are laid down .Surface texture of the aggregate affects its bond to the cement paste and also influence the water demand of the mix, especially in the case of fine aggregate. The shape and surface texture of aggregate influence considerably the strength of concrete. The effects of shape and texture are particularly significant in the case of high strength concrete. The full role of shape and texture of aggregate in the development of concrete strength is not known, but possibly a rougher texture results in a larger adhesive force between the particles and the cement matrix. The shape and texture of fine aggregate have a significant effect on the water requirement of the mix made with the given aggregate. If these properties of fine aggregate are expressed indirectly by its packing, i.e. by the percentage voids in a loose condition, then the influence on the water requirement is quite definite. The influence of the voids in coarse aggregate is less definite. Flakiness and shape of coarse aggregates have an appreciable effect on the workability of concrete.
  22. 22. 22 3.1.2.1.5 Bond of aggregate: Bond between aggregate and cement paste is an important factor in the strength of concrete, but the nature of bond is not fully understood. Bond is to the interlocking of the aggregate and the hydrated cement paste due to the roughness of the surface of the former. A rougher surface, such as that of crushed particles, results in a better bond due to mechanical interlocking; better bond is not usually obtained with softer, porous, and minor logically heterogeneous particles. Bond is affected by the physical and chemical properties of aggregate. For good development of bond, it is necessary that the aggregate surface be clean and free from adhering clay particles .The determination of the quality of bond of aggregate is difficult and no accepted tests exist. Generally, when bond is good, a crushed specimen of normal strength concrete should contain some aggregate particles broken right through, in addition to the more numerous ones pulled out from their sockets. An excess of fractured particles, might suggest that the aggregate is too weak. 3.1.2.1.6 Strength of aggregate: The compressive strength of concrete cannot significantly exceed that of the major part of the aggregate contained. If the aggregate under test leads to a lower compressive strength of concrete, and in particular if numerous individual aggregate particles appear fractured after the concrete specimen has been crushed, then the strength of the aggregate is lower than the nominal compressive strength of the concrete mix. Such aggregate can be used only in a concrete of lower strength. The influence of aggregate on the strength of concrete is not only due to the mechanical strength of the aggregate but also, to a considerable degree, to its absorption and bond characteristics. In general, the strength of aggregate depends on its composition, texture and structure. Thus a low strength may be due to the weakness of constituent grains or the grains may be strong but not well knit or cemented together. A test to measure the compressive strength of prepared rock cylinders used to be prescribed. However, the results of such a test are affected by the presence of planes of weakness in the rock that may not be significant once the rock has been reduced to the size used in concrete. In essence the crushing strength test measures the quality of the parent rock rather than the quality of the aggregate as used in concrete. For this reason the test is rarely used. Crushing value test BIS: 812-1990, measures the resistance to pulverization. There is no obvious physical relation between this crushing value and the compressive strength, but the results of the two tests are usually in agreement.
  23. 23. 23 3.1.2.1.7 Deleterious substances of aggregate: For satisfactory performance, concrete aggregates should be free of deleterious materials. There are three categories of deleterious substances that may be found in aggregates: impurities, coatings and weak or unsound particles. 3.1.2.1.8 Grading of fine and coarse aggregate: The actual grading requirements depend on the shape and surface characteristics of the particles. For instance, sharp angular particles with rough surfaces should have a slightly finer grading in order to reduce the possibility of interlocking and to compensate for the high friction between the particles 3.1.2.1.9 Maximum aggregate size: Extending the grading of aggregate to a larger maximum size lowers the water requirement of the mix, so that, for a specified workability and cement content, the water /cement ratio can be lowered with a consequent increase in strength. Experimental results indicated that above the 38.1mm maximum size the gain in strength due to the reduced water requirement is offset by the detrimental effects of lower bond area of discontinuities introduced by the very large particles. In structural concrete of usual proportions, there is no advantage in using aggregate with a maximum size greater than about 25 or 40mm when compressive strength is a criterion. The standard type aggregate for use in pervious concrete is typically crushed stone or river gravel. Typical sizes are from 10mm to 25mm. (Tennis et al 2004). Fine aggregates are either used sparingly or removed altogether from the mix design. It has been shown that using smaller aggregates increases the compressive strength of pervious concrete by providing a tighter bond between coarse aggregate and cement. Using fine aggregates in the mix design of pervious concrete will also decrease the void space (Tennis et al 2004). Increasing the percent amount of larger aggregates will increase the void ratio in pervious concrete, but will decrease the compressive strength. Using recycled aggregates has also been researched. Four mix designs were studied using 15%, 30%, 50%, and 100% recycled aggregates and compared to the virgin pervious concrete samples. It was found that samples containing 15% or less recycled aggregates exhibited almost identical characteristic to the virgin sample.
  24. 24. 24 The size of the aggregate also has an important role in pervious concrete. While a 20mm aggregate size allows for greater void space, a 20mm aggregate improves the workability. The use of 10mm aggregate can decrease settling and workability. Recent studies have also found that pervious concrete with smaller aggregates had higher compressive strength. It was noted that the smaller aggregate sizes allowed for more cementitious material to bind around the aggregate and hence allowed for greater contact between the aggregate/binder 3.1.2.2FINE AGGREGATES: While pervious concrete is considered a “no-fines” concrete, a small percentage of fine particles can be added to increase the compressive strength of the pervious concrete mix. The inclusion of fine particles has a direct correlation to the paste/mortar strength. Providing a thicker paste layer around the coarse aggregates results in improved compressive strength (Schaefer et al 2009). There is a significant relationship between compressive strength and sand to gravel ratio. When the sand to gravel ratio is increased to 8 %, the mortar bulks up and increases the strength. When the sand to gravel ratio increases beyond the 8 % mark, the 7 day compressive strength begins to fall (Schaefer et al 2009). Both Europe and Japan have been using smaller aggregates as well as the inclusion of sand for their mix design. An optimization of 10%-20% of fine sand to coarse aggregate has been shown to increase compressive strength from 14 to 19 MPa. A slight decrease in permeability correlates to the increase in fine particles. Figure3.3: Fine aggregates
  25. 25. 25 Figure3.4: Relationships between Fine Aggregate and Porosity/Compressive Strength 3.1.3 WATER: While any potable water can be used for mixing, the amount of water is critical for the formation of the voids in pervious concrete. Water-to-cement ratios can range from 0.27 to 0.30 with ratios as high as 0.40. Careful control of water is critical. A mix design with little water can create a very weak binder. This will create a very dry mix that is susceptible to spalling and crumbling. A mix design with too much water can collapse the void space, making an almost impenetrable concrete surface (NRMCA 2004).
  26. 26. 26 As seen in Figure, the specimen in Figure (a) has too little water, the specimen in Figure (b) has the correct amount of water, and the specimen in Figure (c) has too much water. (a) (b) (c) Figure 3.5: Pervious Concrete With a. too little Water, b. Appropriate Amount of Water, c. Too much Water
  27. 27. 27 A study done by Meininger (1998) demonstrated the relationship between compressive strength and water-to-cement ratio. The optimal w/c ratio with the highest compressive strength was found to be between 0.3 and 0.35. Lower w/c ratios provide poor cohesion between the aggregates. Higher w/c ratios reduce the tensile capacity by the introduction of capillary pores. Figure 3.6: graph showing relation between w/c ratio and compressive strength of concrete (Meininger, 1998) Another study by Chindaprasirt, Hatanaka, Chareerat, Mishima, and Yuasa determined that water-to-cement ratio has a direct correlation to cement paste characteristics, and mixing time of the porous concrete. It was noted that keeping a relatively low water-to- cement ratio, around 0.2 to 0.3, maintains the continuity of the paste layer with coarse aggregate. This also aids in the texture and workability of the pervious concrete. By achieving an even thickness of the paste (150-230 mm) within the porous concrete mix, this can achieve suitable void ratios of 15-25% and strengths ranges from 22-30 MPa.
  28. 28. 28 3.1.4 SUPPLEMENTARYCEMENTITIOUS MATERIALS (SCMS): SCM includes fly ash, pozzolans, and slag can be added to the cement. These influence concrete performance, setting time, rate of strength development, porosity, permeability, etc., The key to high-performance concrete is the use of SCMs. Silica fume, fly ash, and blast furnace slag all increase durability by decreasing permeability and cracking  Silica fume is a by-product of silicone production. It consists of superfine spherical particles which significantly increase the strength and durability of concrete. Used frequently for high-rise buildings, it produces concrete that exceeds 140 MPa compressive strength. Silica fume can replace cement in quantities of 5-12%.  Fly ash is the waste by-product of burning coal in electrical power plants; it used to be land filled, but now a significant amount is used in cement. This material can be used to replace 5-65% of the Portland cement  Blast furnace slag is the waste by-product of steel manufacturing. It imparts added strength and durability to concrete, and can replace 20-70% of the cement in the mix. In our project work, we have used fly ash and rice husk ash and mixture of both fly ash and rice husk ash as the partial replacement of cement in the quantities of 10% of cement. 3.1.4.1 Fly ash: Fly ash, also known as "pulverised fuel ash", is one of the coal combustion products, composed of the fine particles that are driven out of the boiler with the flue gases. Ash that falls in the bottom of the boiler is called bottom ash. In modern coal-fired power plants, fly ash is generally captured by electrostatic precipitators or other particle filtration equipment before the flue gases reach the chimneys. Together with bottom ash removed from the bottom of the boiler, it is known as coal ash. Depending upon the source and makeup of the coal being burned, the components of fly ash vary considerably, but all fly ash includes substantial amounts of silicon dioxide (SiO2) (both amorphous and crystalline), aluminium oxide (Al2O3) and calcium oxide (CaO), the main mineral compounds in coal-bearing rock strata.
  29. 29. 29 In the past, fly ash was generally released into the atmosphere, but air pollution control standards now require that it be captured prior to release by fitting pollution control equipment. In the US, fly ash is generally stored at coal power plants or placed in landfills. About 43% is recycled, often used as a pozzolan to produce hydraulic cement or hydraulic plaster and a replacement or partial replacement for Portland cement in concrete production. Pozzolans ensure the setting of concrete and plaster and provide concrete with more protection from wet conditions and chemical attack. After a long regulatory process, the EPA published a final ruling in December 2014, which establishes that coal fly ash is regulated on the federal level as "non-hazardous" waste according to the Resource Conservation and Recovery Act (RCRA). Coal Combustion Residuals (CCR's) are listed in the subtitle D (rather than under subtitle C dealing for hazardous waste, which was also considered). In the case that fly or bottom ash is not produced from coal, for example when solid waste is used to produce electricity in an incinerator, this kind of ash may contain higher levels of contaminants than coal ash. In that case the ash produced is often classified as hazardous waste. 3.1.4.1.1 Chemical Composition and Classification Fly Ash: Fly ash material solidifies while suspended in the exhaust gases and is collected by electrostatic precipitators or filter bags. Since the particles solidify rapidly while suspended in the exhaust gases, fly ash particles are generally spherical in shape and range in size from 0.5 µm to 300 µm. The major consequence of the rapid cooling is that few minerals have time to crystallize, and that mainly amorphous, quenched glass remains. Nevertheless, some refractory phases in the pulverized coal do not melt (entirely), and remain crystalline. In consequence, fly ash is a heterogeneous material. SiO2, Al2O3, Fe2O3 and occasionally CaO are the main chemical components present in fly ashes. The mineralogy of fly ashes is very diverse. The main phases encountered are a glass phase, together with quartz, mullite and the iron oxides hematite, magnetite and/or maghemite. Other phases often identified are cristobalite, anhydrite, freelime, periclase, calcite, sylvite, halite, portlandite, rutile and an atase. The Ca-bearing minerals anorthite, gehlenite, akermanite and various calcium silicates and calcium aluminates identical to those found in Portland cement can be identified in Ca- rich fly ashes.
  30. 30. 30 Table3.2: Chemical composition of fly ash and pond ash Compounds (%) Fly Ash Pond Ash SiO2 38-63 37-75 Al2O3 27-44 28-53 TiO2 0.4-1.8 0-1 Fe2O3 3.3-6.4 17-34 MnO 0.1-0.5 0.1-0.6 MgO 0.01-0.5 0.1-0.8 CaO 0.2-8 0.2-0.6 K2 O 0.04-0.9 0.1-0.7 Na2O 0.07-0.43 0.05-0.31 LOI 0.2-5.0 0.01-20.0 pH 06-09 06-08 Two classes of fly ash are defined by ASTM C618: Class F fly ash and Class C fly ash. The chief difference between these classes is the amount of calcium, silica, alumina, and iron content in the ash. The chemical properties of the fly ash are largely influenced by the chemical content of the coal burned (i.e., anthracite, bituminous, and lignite). Not all fly ashes meet ASTM C618 requirements, although depending on the application, this may not be necessary. Ash used as a cement replacement must meet strict construction standards, but no standard environmental regulations have been established in the United States. 75% of the ash must have a fineness of 45 µm or less, and have a carbon content, measured by the loss on ignition (LOI), of less than 4%. In the U.S., LOI must be under 6%. The particle size distribution of raw fly ash tends to fluctuate constantly, due to changing performance of the coal mills and the boiler performance. This makes it necessary that, if fly ash is used in an optimal way to replace cement in concrete production, it must be processed using beneficiation methods like mechanical air classification.
  31. 31. 31 3.1.4.1.2 Fly Ash as Replacement of Cement: Owing to its pozzolanic properties, fly ash is used as a replacement for Portland cement in concrete. The use of fly ash as a pozzolanic ingredient was recognized as early as 1914, although the earliest noteworthy study of its use was in 1937. Roman structures such as aqueducts or the Pantheon in Rome used volcanic ash or pozzolana (which possesses similar properties to fly ash) as pozzolan in their concrete. Use of fly ash as a partial replacement for Portland cement is particularly suitable but not limited to Class C fly ashes. Class "F" fly ashes can have volatile effects on the entrained air content of concrete, causing reduced resistance to freeze/thaw damage. Fly ash often replaces up to 30% by mass of Portland cement, but can be used in higher dosages in certain applications. Figure3.7: Fly ash used as cement replacement Fly ash can significantly improve the workability of concrete. Recently, techniques have been developed to replace partial cement with high-volume fly ash (50% cement replacement). For roller-compacted concrete (RCC) replacement values of 70% have been achieved with processed fly ash at the Ghatghar dam project in Maharashtra, India. Due to the spherical shape of fly ash particles, it can increase workability of cement while reducing water demand. Proponents of fly ash claim that replacing Portland cement with fly ash reduces the greenhouse gas "footprint" of concrete, as the production of one ton of Portland cement generates approximately one ton of CO2, compared to no CO2 generated with fly ash. New fly ash production, i.e., the burning of coal, produces approximately 20 to 30 tons of CO2 per ton of fly ash.
  32. 32. 32 3.1.4.2 Rice Husk Ash: 3.1.4.2.1 Chemical Composition and Properties of Rice husk ash: Rice husk can be burnt into ash that fulfils the physical characteristics and chemical composition of mineral admixtures. Pozzolanic activity of rice husk ash (RHA) depends on (i) silica content, (ii) silica crystallization phase, and (iii) size and surface area of ash particles. In addition, ash must contain only a small amount of carbon.RHA that has amorphous silica content and large surface area can be produced by combustion of rice husk at controlled temperature. Suitable incinerator/furnace as well as grinding method is required for burning and grinding rice husk in order to obtain good quality ash. Although the studies on pozzolanic activity of RHA, its use as a supplementary cementitious material, and its environmental and economical benefits are available in many literatures, very few of them deal with rice husk combustion and grinding methods. The optimized RHA, by controlled burn and/or grinding, has been used as a pozzolanic material in cement and concrete. Using it provides several advantages, such as improved strength and durability properties, and environmental benefits related to the disposal of waste materials and to reduced carbon dioxide emissions. For this reason, this study investigates the strength activity index of mortars containing residual RHA that is generated when burning rice husk pellets and RHA as received after grinding residual RHA. The effect of partial replacement of cement with different percentages of ground RHA on the compressive strength and durability of concrete is examined. Figure3.8: Rice Husk Ash
  33. 33. 33 Table3.3: Chemical Properties of R.H.A S.No Particulars Proportion 1 Silicon Dioxide 86.94% 2 Aluminium Oxide 0.20% 3 Iron Oxide 0.10% 4 Calcium Oxide 0.3 – 2.25% 5 Magnesium Oxide 0.2 – 0.6% 6 Sodium Oxide 0.1 -0.8% 7 Potassium Oxide 2.15 – 2.30% 3.1.4.2.2 Rice Husk Ash as Cement Replacement: Rice husk ash is used in concrete construction as an alternative of cement. The rice paddy milling industries give the by-product rice husk. Due to the increasing rate of environmental pollution and the consideration of sustainability factor have made the idea of utilizing rice husk. To have a proper idea on the performance of rice husk in concrete, a detailed study on its properties must be done. About 100 million tons of rice paddy manufacture by-products are obtained around the world. They have a very low bulk density of 90 to 150kg/m3. This results in a greater value of dry volume. The rice husk itself has a very rough surface which is abrasive in nature. These are hence resistant to natural degradation. This would result in improper disposal problems. So, a way to use these by-products to make a new product is the best sustainable idea. Among all industries to reuse this product, cement, and concrete manufacturing industries are the ones who can use rice husk in a better way. The rice husk ash has good reactivity when used as a partial substitute for cement. These are prominent in countries where the rice production is abundant. The properly rice husk ashes are found to be active within the cement paste. So, the use and practical application of rice husk ash for concrete manufacturing are important. The incorporation of rice husk ash in concrete converts it into an eco-friendly supplementary cementitious material.
  34. 34. 34 The following properties of the concrete are altered with the addition of rice husk  The heat of hydration is reduced. This itself help in drying shrinkage and facilitate durability of the concrete mix.  The reduction in the permeability of concrete structure. This will help in penetration of chloride ions, thus avoiding the disintegration of the concrete structure.  There is a higher increase in the chloride and sulphate attack resistance The rice husk ashes in the concrete react with the calcium hydroxide to bring more hydration products. The consumption of calcium hydroxide will enable lesser reactivity of chemicals from the external environment. 3.2 MIX DESIGN OF PERVIOUS CONCRETE 3.2.1 Void Content: At a void content lower than 15%, there is no significant percolation through the concrete due to insufficient interconnectivity between the voids to allow for rapid percolation. So, concrete mixtures are typically designed for 20% void content in order to attain sufficient strength and infiltration rate. 3.2.2 Unit Weight or Density: The density of pervious concrete depends on the properties and proportions of the materials used, and on the compaction procedures used in placement. In-place densities on the order of 1600 kg/m³ to 2100 kg/m³ are common, which is in the upper range of lightweight concretes. A pavement 125 mm thick with 20% voids will be able to store 25 mm of a sustained rainstorm in its voids, which covers the vast majority of rainfall events in the U.S. When placed on a 150mm thick layer of open-graded gravel or crushed rock sub base, the storage capacity increases to as much as 75 mm of precipitation.
  35. 35. 35 3.2.3 Water – Cement Ratio: The water-cementitious material ratio (w/cm) is an important consideration for obtaining desired strength and void structure in pervious concrete. A high w/cm reduces the adhesion of the paste to the aggregate and causes the paste to flow and fill the voids even when lightly compacted. A low w/cm will prevent good mixing and tend to cause balling in the mixer, prevent an even distribution of cement paste, and therefore reduce the ultimate strength and durability of the concrete. w/cm in the range of 0.26 to 0.40 provides the best aggregate coating and paste stability. The conventional w/cm-versus-compressive strength relationship for normal concrete does not apply to pervious concrete. Careful control of aggregate moisture and w/cm is important to produce consistent pervious concrete. 3.2.4 Cement Content: The total cementitious material content of a pervious concrete mixture is important for the development of compressive strength and void structure. An insufficient cementitious content can result in reduced paste coating of the aggregate and reduced compressive strength. The optimum cementitious material content is strongly dependent on aggregate size and gradation but is typically between 267 and 415 kg/m3. The above guidelines can be used to develop trial batches. ASTM C1688 provides the tests to be conducted in the laboratory to observe if the target void contents are attained. Figure3.9: Arrangement of pervious concrete for pavements
  36. 36. 36 3.2.5 Mix Design Criteria: Pervious concrete uses the same materials as conventional concrete, except that there is usually little or no fine aggregate. The quantity, proportions, and mixing techniques affect many properties of pervious concrete, in particular the void structure and strength. Usually single sized coarse aggregate up to 20 mm size normally adopted. Larger size aggregates provide a rougher concrete finish while smaller size aggregates provide smoother surface that may be better suited for some application such as pedestrian pathways. Although the coarse aggregate size 6 mm to 20 mm are used, the most common being 10 mm fairly uniform size is used. The aggregates may be rounded like gravel or angular like crushed stone Since the pervious concrete is highly permeable, the voids between aggregate particles cannot be entirely filled by cement paste. Use of smaller size aggregates can increase the number of aggregate particles per unit volume of concrete. As the aggregate particle increase the specific surface and thus increases the binding area. This results in the improved strength of pervious concrete. However, the major thrust for using pervious concrete stems from its capability to drain and potentially de-pollute enormous amounts of water in short time, thus reducing the runoff rates. The physical and mechanical properties of pervious concretes are reported elsewhere (Onstenk, 1993, Neithalath, 2004, Neithalath, 2005, Neithalath, 2006, Nelson, 1994). The use of larger size aggregates reduces clogging of pores in the pervious concrete. The water permeation capacity or drainage properties are closely related to the porosity with coefficient of permeability to about 0.01m/s is recommended. A drainage rate of 100 to 270 lit/m2/min has been reported for pervious concrete with a porosity ranging from 17% to 28% (Tennis, 2004). Recently it is suggested that the aggregate sizes of pervious concrete should be between 9.5 mm and 19 mm and no fine aggregate should be used. The binder normally used in ordinary Portland cement (OPC). Pozzolanic materials like fly ash, blast furnace slag and silica fume can also be used. However, use of pozzolanic materials will affect setting time, strength, porosity and permeability of the resulting concrete. Addition of fine aggregate will reduce the porosity and increase the strength of concrete.
  37. 37. 37 Chemical admixtures like water reducing admixture, retarders, hydration stabilizing admixtures, viscosity modifying admixtures and internal curing admixtures are used. Pervious concrete uses same materials as conventional concrete, except that there are usually No or little fine aggregates. The size of the coarse aggregate used is kept fairly uniform in size to minimize surface roughness and for a better aesthetic, however sizes can vary from 6.25 mm to 12.5 mm. Water to cement ratio should be within 0.27 to 0.34. Ordinary Portland cement and blended cements can be used in pervious concrete. Water reducing admixtures and retarders can be used in pervious concrete. General issues encountered compared to standards concrete are 1. Long mixing time in the batching plants (about 20 minutes) 2. Poor workability, very dry mix, difficult for placing 3. Amount of water used in mix is important as same as standards concrete 4. If too much water used, segregate is expected, usually higher than standards concrete 5. If too little water is used, not easy to mix, balling of mix in the mixer. Table3.4: Typical mix design of pervious concrete as suggested by ACI 522 R-10 Materials Proportions (Kg/m3) Cement (OPC or blended) 270 to 415 Aggregate 1190 to 1480 Water: cement ratio (by mass) 0.27 to 0.34 Fine: coarse aggregate ratio (by mass) 0 to 1:1 Chemical admixtures (retarders) are commonly used and Addition of fine aggregates will decrease the void content and increase strength
  38. 38. 38 Figure3.10: preparation of pervious concrete cubes 3.2.6 NRMCA procedure for Pervious Concrete Mixture Proportioning: The following mixture proportioning approach can be used to quickly arrive at pervious concrete mixture proportions that would help attain void content of freshly mixed pervious concrete when measured in accordance with ASTM C1688 similar to the target value. (1) Determine the dry-rodded unit weight of the aggregate and calculate the void content. Estimate the approximate percentage and volume of paste needed. The paste volume (PV) is then estimated as follows: Vp (%) = Aggregate Void Content (%) + CI (%) - Vvoid (%) Where, CI = compaction index and Vvoid = design void content of the pervious concrete mix.
  39. 39. 39 The value of CI can be varied based on the anticipated consolidation to be used in the field. For greater consolidation effort a compaction index value of 1 to 2% may be more reasonable. For lighter level of consolidation a value of 7 to 8% can be used. NRMCA used a value of 5% to get similar values between measured fresh pervious concrete void content (ASTM C1688) and design void content. Using a smaller value for CI (%) will reduce the paste volume. (2) Calculate the paste volume, Vp in ft3 per cubic yard of pervious concrete: Vp, ft3 = Vp (%) × 27 (3) Select the w/c ratio for the paste. Recommended values are in the range of 0.25 to 0.36. (4) Calculate the absolute volume of cement vc,ft3 = vp/[1+(w/c*RDc)] Where: RDc is the specific gravity of cement (typically 3.15) (5) Calculate the volume of water, Vw Vw, ft3 = Vp – Vc (6) Calculate the volume of SSD aggregate (Vagg) Vagg = 27 – (Vp +Vvoid) Where: Vvoid is the design void content for the pervious concrete mix. Convert the volumes to weights of ingredients per cubic yard and for trial batches: Cement (lb/yd3) = Vc × RDc × 62.4 Water (lb/yd3) = Vw × 62.4 SSD Coarse Aggregate (lb/yd3) = Vagg × RDagg × 62.4 Trial batches are prepared to evaluate mix characteristics of the pervious concrete mixture. Make appropriate adjustments are made to account for aggregate moisture content. If paste is high, pick a lower value or change CI (%). Avoid excessive cementitious content should be avoided. The consistency of the paste can be evaluated separately to ensure that it is not too dry or causes paste run down by being too wet. The density of the mixture should be measured in accordance with ASTM C1688 from which the void content is calculated to ensure that values are in line with the design void content. Then evaluate mixture for consistency, specification requirements and placement method used by the pervious concrete contractor.
  40. 40. 40 NRMCA has developed a pervious concrete mixture proportioning guideline and spreadsheet software that will develop trial batch mixture proportions using volumetric considerations and make the necessary calculations for production batches when mixture proportions are finalized after trial batch evaluations. 3.3 COMPRESSIVE STRENGTHAND PERMEABILITYOF PERVIOUS CONCRETE 3.3.1 Compressive Strength of Normal Concrete: Out of many test applied to the concrete, this is the utmost important which gives an idea about all the characteristics of concrete. By this single test one judge that whether Concreting has been done properly or not. Compressive strength of concrete depends on many factors such as water-cement ratio, cement strength, quality of concrete material, Quality control during production of concrete etc., Test for compressive strength is carried out either on cube or cylinder. Various standard codes recommend concrete cylinder or concrete cube as the standard specimen for the test. For cube test two types of specimens either cubes of 150 mm X 150 mm X 15 mm or 100 mm X 100 mm x 100 mm depending upon the size of aggregate are used. For most of the works cubical moulds of size 150 mm x 150 mm x 150 mm are commonly used. This concrete is poured in the mould and tempered properly so as not to have any voids. After 24 hours these moulds are removed and test specimens are put in water for curing. The top surface of these specimen should be made even and smooth. This is done by putting cement paste and spreading smoothly on whole area of specimen.
  41. 41. 41 Figure3.11: Standard compressive strength cube mould These specimens are tested by compression testing machine after 7 days curing or 28 days curing. Load should be applied gradually at the rate of 140 kg/cm2 per minute till the Specimens fails. Load at the failure divided by area of specimen gives the compressive strength of concrete. 3.3.1.1 Preparation of Cube Specimens The proportion and material for making these test specimens are from the same concrete used in the field. 3.3.1.2 Mixing Mix the concrete either by hand or in a laboratory batch mixer Figure3.12: mixing of pervious concrete
  42. 42. 42 3.3.1.3 Hand Mixing: (i)Mix the cement and fine aggregate on a water tight none-absorbent platform until the mixture is thoroughly blended and is of uniform colour (ii)Add the coarse aggregate and mix with cement and fine aggregate until the coarse aggregate is uniformly distributed throughout the batch (iii)Add water and mix it until the concrete appears to be homogeneous and of the desired consistency 3.3.1.4 Sampling (i) Clean the mounds and apply grease. (ii) Fill the concrete in the moulds in 3 equal layers (iii) Compact each layer with not less than 35strokes per layer using a tamping rod (steel bar 16mm diameter and 60cm long, bullet pointed at lower end) (iv) Level the top surface and smoothen it with a trowel Figure3.13: compaction of pervious concrete with tamping rod
  43. 43. 43 3.3.1.5 Curing The test specimens are stored in moist air for 24hours and after this period the specimens are marked and removed from the moulds and kept submerged in clear fresh water until taken out prior to test. 3.3.1.6 Procedure: (I) Remove the specimen from water after specified curing time and wipe out excess water from the surface. (II) Take the dimension of the specimen to the nearest 0.2m (III) Clean the bearing surface of the testing machine (IV) Place the specimen in the machine in such a manner that the load shall be applied to the opposite sides of the cube cast. (V) Align the specimen centrally on the base plate of the machine. (VI) Rotate the movable portion gently by hand so that it touches the top surface of the specimen. (VII) Apply the load gradually without shock and continuously at the rate of 140kg/cm2/minute till the specimen fails (VIII) Record the maximum load and note any unusual features in the type of failure. 3.3.1.7 NOTE: Minimum three specimens should be tested at each selected age. If strength of any specimen varies by more than 15 per cent of average strength, results of such specimen should be rejected. Average of these specimens gives the crushing or compressive strength of concrete. The strength of concrete increases with increase in age. The following table shows the strength of concrete at different ages in comparison with the strength at 28 days after casting.
  44. 44. 44 Table3.5: Compressive strength of concrete at various ages Age Strength per cent 1 day 16% 3 days 40% 7 days 65% 14 days 90% 28 days 99% Table3.6: Compressive strength of different grades of concrete at 7 and 28 days Grade of Concrete Minimum compressive strength N/mm2 at 7 days Specified characteristic compressive strength (N/mm2) at 28 days M15 10 15 M20 13.5 20 M25 17 25 M30 20 30 M35 23.5 35 M40 27 40 M45 30 45 3.3.2 COMPRESSIVE STRENGTH OF PERVIOUS CONCRETE: In the laboratory, pervious concrete mixtures have been found to develop compressive strengths in the range of 3.5 MPa to 28 MPa, which is suitable for a wide range of applications. Typical values are about 17 MPa. As with any concrete, the properties and combinations of specific materials, as well as placement techniques and environmental conditions, will dictate the actual in-place strength. However, currently there is no ASTM test standard for compressive strength of pervious concrete.
  45. 45. 45 Testing variability measured with various draft test methods has been found to be high and therefore compressive strength is not recommended as an acceptance criterion. Rather, it is recommended that a target void content (between 15% to 25%) as measured by ASTM C 1688: Standard Test Method for Density and Void Content of Freshly Mixed Pervious Concrete be specified for quality assurance and acceptance. Figure3.14: cubes tested for compressive strength 3.3.3 DENSITY AND POROSITY: Figure3.15: Typical cross section of pervious concrete for pavement. The density of pervious concrete depends on the properties and proportions of the materials used, and on the compaction procedures used in placement. In-place densities on the order of 1600 kg/m³ to 2100 kg/m³ are common, which is in the upper range of lightweight concretes. A pavement 125 mm thick with 20% voids will be able to store 25 mm of a sustained rainstorm in its voids, which covers the vast majority of rainfall events in the U.S.
  46. 46. 46 3.3.4 PERMEABILITY OF PERVIOUS CONCRETE: The permeability of pervious concrete was determined using a falling head permeability set up Figure 8. Water was allowed to flow through the sample, through a connected standpipe which provides the water head. Before starting the flow measurement, the samples were wrapped with polythene inside the cylinder. Then the test started by allowing water to flow through the sample until the water in the standpipe reached a given lower level. A constant time of 5seconds was taken for the water to fall from one head to another in the standpipe. The standpipe was refilled and the test was repeated when water reached a lower. The permeability of the pervious concrete sample was evaluated from the expression given below: Figure3.16: variable head permeability test apparatus
  47. 47. 47 Formula: K=2.303 aL/A (t2-t1) log (h1/h2) Where, a = the sample cross section area A = the cross section of the standpipe of diameter (d) = 0.95cm2 L = the height of the pervious concrete (t2 - t1) = change in time for water to fall from one level to another (5secs.) h1= upper water level h2= Lower water level D= diameter of sample (10.5cm) d= diameter of standpipe (1.1cm) Theoretically, the coefficient of permeability generally in the order of 1mm/sec for a void ratio of 20% and the rate of flow is in the range of 120 litres/min/m2 to 200 litres/min/m2 In general, the concrete permeability limitation is not a critical design criterion. Consider a passive pervious concrete pavement system overlying a well-draining soil. Designers should ensure that permeability is sufficient to accommodate all rain falling on the surface of the pervious concrete. For example, with a permeability of 140 L/m2/min, a rainfall in excess of 0.24 cm/s would be required before permeability becomes a limiting factor. The permeability of pervious concretes is not a practical controlling factor in design. However, the flow rate through the sub grade may be more restrictive.
  48. 48. 48 3.3.5 Storage Capacity: Storage capacity of a pervious concrete system typically is designed for specific rainfall events, which are dictated by local requirements. The total volume of rain is important, but the infiltration rate of the soil also must be considered. The total storage capacity of the pervious concrete system includes the capacity of the pervious concrete pavement, the capacity of any sub base used, and the amount of water which leaves the system by infiltration into the underlying soil. The theoretical storage capacity of the pervious concrete is its effective porosity: that portion of the pervious concrete which can be filled with rain in service. If the pervious concrete has 15% effective porosity, then every 25 mm of pavement depth can hold 4 mm of rain. For example, a 100mm thick pavement with 15% effective porosity on top of impervious clay could hold up to 15 mm of rain before contributing to excess rainfall runoff. Another important source of storage is the sub base. A conventional aggregate sub base, with higher fines content, will have a lower porosity (about 20%). From the example above, if 100 mm of pervious concrete with 15% porosity was placed on 150 mm of clean stone, the nominal storage capacity would be 75 mm of rain. The effect of the sub base on the storage capacity of the pervious concrete pavement system can be significant. A critical assumption in this calculation is that the entire system is level. If the top of the slab is not level, and the infiltration rate of the sub grade has been exceeded, higher portions of the slab will not fill and additional rainfall may run to the lowest part of the slab. Once it is filled, the rain will run out of the pavement, limiting the beneficial effects of the pervious concrete. These losses in useable volume because of slopes can be significant, and indicate the sensitivity of the design to slope. Pipes extending from the trenches carry water travelling down the paved slope out to the adjacent hillside. The high flow rates that can result from water flowing down slope also may wash out sub grade materials, weakening the pavement.
  49. 49. 49 3.4 Improvement of Strength of Pervious Concrete:  As the strength of pervious concrete is less when compared to conventional concrete, its applications are limited to great extent  The main aim of our project is to improve the strength of pervious concrete so that it can be used for large number of applications  The strength improvement can be done by (1) Addition of small quantity of fine aggregates (2) Addition of small quantities of cementitious materials (3) Usage of small sized coarse aggregates (4) Using low w/c ratio etc.,  Among the above methods, we have selected addition of small quantity of fine aggregates, addition of cementitious materials such as fly ash, rice husk ash and mixture of both fly ash and rice husk ash.  The compressive strength of pervious concrete inversely proportional to permeability. As the compressive strength increases, the permeability will be decreased and vice- versa.  The main purpose of pervious concrete is permeability. By improving the strength we should not forget the effect of permeability.  In our project work, we have considered both the aspects. We tried to improve the compressive strength of pervious concrete without compromising the permeability much.  Theoretically, it is stated that the strength characteristics will be increased if the fine aggregates are added 5-10% quantity of coarse aggregates.
  50. 50. 50 Chapter-4 RESULTS AND DISCUSSIONS 4.1 Optimised Mix Design of Pervious Concrete (With 20mm Aggregates, No Sand), Tested At NEC Nellore concrete technology laboratory: Properties of materials tested in the laboratory: 4.1.1 Tests on cement: OPC-53 grade cement: Table4.1: properties of cement tested at Concrete technology laboratory S.No Property Value 1 Specific gravity 3.15 2 Bulk density 1120 kg/m3 3 Fineness 225 m2/kg 4 Initial setting time 35 min 5 Final setting time 132 min 6 Consistency 28% 4.1.2 Tests on coarse aggregates: Coarse aggregates (locally available 20mm size aggregates): Table4.2: properties of coarse aggregates tested at Concrete technology laboratory S.No Property Value 1 Bulk density 1583.34 kg/m3 2 Impact strength 26.4% 3 Crushing strength 25.45% 4 Void content 37.16% 5 Specific gravity 2.65
  51. 51. 51 4.1.3 Tests on fine aggregates: Fine aggregates (locally available): Table4.3: properties of fine aggregates tested at Concrete technology laboratory S.No Property Value 1 Specific gravity 2.62 2 Fineness modulus 2.5 3 Dry rodded unit weight 1720 kg/m3 4 Water absorption 0.6% 4.1.4 Optimised mix proportions: Optimised mix proportion is calculated with 20mm coarse aggregate as standard pervious concrete:  The void ratio and unit weight are the important factors to be considered in mix design process  According to mix design, the quantity of cement calculated for one cubic meter of pervious concrete is 390 kgs based on NRMCA, USA  The other important considerations are aggregate to cement (A/C) ratio and water to cement (W/C) ratio. We can consider different types of aggregates to cement ratios and water to cement ratios as per our requirement.  The mix design procedure gave the value of cement to aggregate ratio as 1:4.25 or approximately 1:4 for the size of aggregates passing through 20mm and retained on 10mm IS sieve  The W/C ratio for the pervious concrete should be in the range of 0.25 to 0.36. For the proper workability we have selected the W/C ratio as 0.3 and it is fixed after doing samples with water to cement ratios o 0.25, 0.30 and 0.35.  The design void ratio of pervious concrete is 20% and the unit weight ranges from 1600 to 2100 kg/m3
  52. 52. 52  The quantities of Materials as per mix design Cement = 390 kg/m3 Coarse aggregates = 1669.2 kg/m3 Water = 117 liters Table4.4: optimised mix proportions Materials Proportions (Kg/m3) Cement (OPC-53 grade) 390 Aggregate (20mm) 1669.2 Water: cement ratio (by mass) 0.3 Fine aggregates 0  The cement we used in our project work is Ordinary Portland Cement of 53 grade  The size of coarse aggregates is passing 20 mm and retained on 10 mm IS sieve  The water used is available in the laboratory. 4.2 Compressive strength of Standard Pervious Concrete with 0% Fines: Quantities of materials: Cement = 390 kg/m3 Coarse aggregates = 1669.73 kg/m3 Fine aggregates = 0 kg/m3 Water = 117 litres per CUM The following table provides the information of compressive strength of standard pervious concrete with 0% fine aggregates tested for 7,14 and 28 days in compression testing machine, permeability tested in variable head permeability test after 28 days and also unit weight of concrete after 24 hours from preparation of concrete.
  53. 53. 53 4.2(a) COMPRESSIVE STRENGTH: Table4.5: compressive strength and unit weight of standard pervious concrete (0%fines) S.No Age of concrete (days) Compressive Strength Of Standard Pervious Concrete (MPa) Unit Weight After 24 Hours(Kg/m3) 1 7 16.72 2112.202 14 19.26 3 28 21.06 4.2(b) Compressive strength comparison between Normal concrete and Pervious concrete: Table4.6: Comparison of strength between normal concrete and pervious concrete S.NO Age of concrete (days) Normal Concrete of M20 (MPa) Pervious Concrete(MPa) 1 7 18.53 16.72 2 14 25.67 19.26 3 28 28.20 21.06 Figure4.1: Graph of showing relation between compressive strength of normal and pervious concrete The compressive strength of pervious concrete is less than the normal concrete due to the absence of fine aggregates or presence of voids. It should be noted that the normal concrete is completely impermeable in nature. 0 5 10 15 20 25 30 normal concrete 0%fines pervious concrete CompressivestrengthinMPa Types of concrete compressive strength comparison 7days 14 days 28 days
  54. 54. 54 4.3 Compressive strength of pervious concrete with the addition of fine aggregates 4.3.1 Addition of 5% Fines in Total Coarse Aggregate Quantity Quantities of materials: Cement : Fine aggregates : Coarse aggregates : Water 390 kgs : 83 kgs : 1577 kgs : 117 litres All the materials are calculated for 1 CUM Table4.7: compressive strength and unit weight of pervious concrete with 5% fines S.No Age Of Concrete (days) Compressive strength of pervious concrete with 0% fines(MPa) Compressive Strength Of Pervious Concrete With 5% Fines (MPa) Unit Weight After 24 Hours(Kg/m3 ) 1 7 16.72 17.36 2065.302 14 19.26 19.60 3 28 21.06 21.65 Figure 4.2: graph of Age of concrete Vs compressive strength of 5% fines pervious concrete From the above table and graph, the 7, 14 and 28 days compressive strength of 5% fines pervious concrete is high. The unit weight of 5% fines pervious concrete is less due to less weight fine particles in the place of coarse aggregates. 0 5 10 15 20 25 0% fines 5% fines compressivestrengthinMpa pervious concrete with 0 and 5% fines in % compressive strength comparisons 7 days 14 days 28 days
  55. 55. 55 4.3.2 Addition of 6% Fines in Total Coarse Aggregate Quantity Quantities of materials: Cement = 390 kg/m3 Coarse aggregates = 1560.40 kg/m3 Fine aggregates = 99.6 kg/m3 (6% of coarse aggregates) Water = 117 litres per CUM Table4.8: compressive strength and unit weight of pervious concrete with 6% fines S.No Age of concrete (days) Compressive strength of pervious concrete with 0% fines (MPa) Compressive Strength Of Pervious Concrete With 6% Fines (MPa) Unit Weight After 24 Hours(Kg/m3) 1 7 16.72 17.75 2040.502 14 19.26 19.73 3 28 21.06 22.47 Figure 4.3: Graph of age of concrete Vs compressive strength h of 6% fines pervious concrete 0 5 10 15 20 25 0% fines 6% fines compressivestrengthinMpa pervious concrete with 0 and 6% fines in % compressive strength comparison 7 days 28 days 14 days
  56. 56. 56 4.3.3 Addition Of 7% Fines in Total Coarse Aggregate Quantity Quantities of materials: Cement = 390 kg/m3 Coarse aggregates = 1543.80 kg/m3 Fine aggregates = 116.2 kg/m3 (7% of coarse aggregates) Water = 117 litres per CUM Table4.9: compressive strength and unit weight of pervious concrete with 7% fines S.No Age Of Concrete (days) Compressive Strength Of Pervious Concrete with 0% fines (MPa) Compressive Strength Of Pervious Concrete With 7% Fines (MPa) Unit Weight After 24 Hours(Kg/m3) 1 7 16.72 18.32 2025.872 14 19.26 19.93 3 28 21.06 23.79 Figure 4.4: Graph of Age of concrete Vs compressive strength of 7% fines pervious concrete 0 5 10 15 20 25 o%fines 7%fines compresssivestrengthinMPa Pervious concretewith 0 and 7% fines in % Compressive strength comparison 7days 14 days 28 days
  57. 57. 57 4.3.4 Addition Of 8% Fines in Total Coarse Aggregate Quantity Quantities of materials: Cement = 390 kg/m3 Coarse aggregates = 1527.20 kg/m3 Fine aggregates = 132.8 kg/m3 (8% of coarse aggregates) Water = 117 litres per CUM Table4.10: compressive strength and unit weight of pervious concrete with 8% fines S.No Age Of Concrete (days) Compressive Strength Of Pervious Concrete with 0% Fines (MPa) Compressive Strength Of Pervious Concrete With 8% Fines (MPa) Unit Weight After 24 Hours(Kg/m3) 1 7 16.72 18.98 1996.652 14 19.26 21.47 3 28 21.06 24.13 Figure 4.5: Graph of Age of concrete Vs compressive strength of 8% fines pervious concrete 0 5 10 15 20 25 30 0%fines 8%fines compresssivestrengthinMPa pervious concrete with 0 and 8% fines in % compressivestrength comparison 7 days 14 days 28 days
  58. 58. 58 4.3.5 Addition Of 9% Fines in Total Coarse Aggregate Quantity Quantities of materials: Cement = 390 kg/m3 Coarse aggregates = 1510.60 kg/m3 Fine aggregates = 149.40 kg/m3 (9% of coarse aggregates) Water = 117 litres per CUM Table4.11: compressive strength and unit weight of pervious concrete with 9% fines S.NO Age of concrete (days) Compressive Strength Of Pervious Concrete with 0% Fines (MPa) Compressive Strength Of Pervious Concrete With 9% Fines (MPa) Unit Weight After 24 Hours(Kg/m3) 1 7 16.72 18.76 1986.26 2 14 19.26 21.23 3 28 21.06 23.47 Figure 4.6: Graph of Age of concrete Vs compressive strength of 9% fines pervious concrete 0 5 10 15 20 25 0%fines 9%fines compresssivestrengthinMPa pervious concrete with 0 and 9% fines in % compressive strength comparison 7 days 14 days 28 days
  59. 59. 59 4.3.6 Addition Of 10% Fines in Total Coarse Aggregate Quantity Quantities of materials: Cement = 390 kg/m3 Coarse aggregates = 1494 kg/m3 Fine aggregates = 166 kg/m3 (10% of coarse aggregates) Water = 117 litres per CUM Table4.12: compressive strength and unit weight of pervious concrete with 10% fines S.NO Age of concrete (days) Compressive Strength Of Pervious Concrete with 0% Fines (MPa) Compressive Strength Of Pervious Concrete With 10% Fines(MPa) Unit Weight After 24 Hours(Kg/m3) 1 7 16.72 18.28 1986.26 2 14 19.26 20.23 3 28 21.06 22.87 Figure4.7: Graph of Age of concrete Vs compressive strength of 10% fines pervious concrete 0 5 10 15 20 25 0%fines 10%fines compresssivestrengthinMPa pervious concrete with 0 and 10% fines in % compressive strength comparison 7 days 14 days 28 days
  60. 60. 60 4.4 compressive strength of pervious concrete with the replacement of cementitious materials: We have tested 3 types of mixes. In the first mix, the fly ash is replaced by 10% of cement. In second mix, Rice Husk Ash is replaced by 10% of cement. In the third mix, mixture of both fly ash (5%) and Rice Husk Ash (5%) is replaced by 10% of cement. 4.4.1 Replacement of Fly ash by 10% of Cement Quantities of materials: Cement : Fly Ash : Coarse Aggregates : Water 351 kgs : 39 kgs : 1510.60 kgs : 117 litres All the materials are calculated for 1 CUM Table4.13: compressive strength and unit weight of pervious concrete with 10% fly ash S.No Age Of Concrete (days) Compressive Strength Of standard Pervious Concrete(MPa) Compressive Strength Of Pervious Concrete 10% Flyash(MPa) Unit Weight After 24 Hours(Kg/M3) 1 7 16.72 17.26 1941.922 14 19.26 19.92 3 28 21.06 22.87 Figure4.8: Graph of Age of concrete Vs compressive strength of 10% fly ash replacement 0 5 10 15 20 25 0%fines 10%flyash compresssivestrengthinMPa pervious concrete with 0 and 10% fly ash replacement compressive strength comparison 7 days 14 days 28days
  61. 61. 61 4.4.2 Replacement of Rice Husk Ash By 10% of Cement Quantities of materials: Cement = 351 kg/m3 Rice husk ash = 39 kg/m3 Coarse aggregates = 1510.60 kg/m3 Water = 117 litres per CUM Table4.14: compressive strength and unit weight of pervious concrete with 10% Rice husk ash S.No Age of Concrete (days) Compressive Strength Of standard Pervious Concrete (MPa) Compressive Strength Of Pervious Concrete 10% Rice Husk Ash(MPa) Unit Weight After 24 Hours(Kg/m3) 1 7 16.72 18.47 1960.602 14 19.26 21.13 3 28 21.06 23.93 Figure4.9: Graph of Age of concrete Vs compressive strength of 10% rice husk ash replacement 0 5 10 15 20 25 0%fines 10%Rice husk ash compresssivestrengthinMPa pervious concrete with 0 and 10% Rice husk ash replacement compressive strength comparison 7 days 14 days 28days
  62. 62. 62 4.4.3 Replacement of Both Fly Ash (5%) And Rice Husk Ash (5%) by 10% of Cement Cement : Coarse aggregates : Water 351 kgs : 1510.60 kgs : 117 litres Fly ash = 19.5 kg/m3 Rice husk ash = 19.5 kg/m3 All the materials are calculated per CUM Table4.15: compressive strength and unit weight of pervious concrete with 10% fly ash and Rice husk ash S.No Age of Concrete (days) Compressive Strength of Standard Pervious Concrete (MPa) Compressive Strength of Pervious Concrete 10% Rice Husk Ash(MPa) Unit Weight After 24 Hours(Kg/m3) 1 7 16.72 16.79 1952.852 14 19.26 20.33 3 28 21.06 23.12 Figure4.10: Graph of Age of concrete Vs compressive strength of 5% fly ash and 5% Rice husk ash replacement From the above three mixes, the cement replacement by mixture of fly ash and rice husk ash gives least values of compressive strength. This may due to different properties of fly ash and rice husk ash may not be homogeneous. 0 5 10 15 20 25 0% fines 5% fly ash and 5% RHA compressivestrengthinMpa pervious concrete with 0 and 5% fly ash and 5% rice husk ash replacement compressivestrength comparison 7 days 28 days 14 days
  63. 63. 63 4.5 PERMEABILITY: The permeability is the property to allow the water to flow through it. Generally, the permeability is determined either by constant head permeability test or by variable head permeability test. In our project work, we have taken variable head permeability test as it suits best for the pervious concrete. To determine the permeability of pervious concrete, we have prepared a beam of size 400*400*60mm. The permeability test is conducted for the standard pervious concrete (0% fines), pervious concrete with 8% fine aggregates, pervious concrete with 10% fine aggregates, pervious concrete with 10% fly ash as cement replacement and pervious concrete with 10% rice husk ash as cement replacement tested after 28 days from preparation. 4.5.1 Permeability of Standard pervious concrete with 0% fine aggregates Quantities of materials: Cement = 390 kg/m3 Coarse aggregates = 1660 kg/m3 Fine aggregates = 0 kg/m3 Water = 117 litres per CUM Table 4.16: unit weight and coefficient of permeability of standard pervious concrete with 0% fines S.No Unit weight of standard pervious concrete (0% fines) after 24 hours (kg/m3) Coefficient of permeability K (cm/sec) 1 2118.84 1.02
  64. 64. 64 4.5.2 Permeability of Pervious concrete with 8% fine aggregates Quantities of materials: Cement = 390 kg/m3 Coarse aggregates = 1527.20 kg/m3 Fine aggregates = 132.80 kg/m3 Water = 117 litres per CUM Table4.17: unit weight and coefficient of permeability of standard pervious concrete with 8% fines S.No Unit weight of standard pervious concrete (0% fines) after 24 hours (kg/m3) Coefficient of permeability K (cm/sec) 1 1998.78 0.76 4.5.3 Permeability of Pervious concrete with 10% fine aggregates Quantities of materials: Cement = 390 kg/m3 Coarse aggregates = 1494 kg/m3 Fine aggregates = 166 kg/m3 Water = 117 litres per CUM Table4.18: unit weight and coefficient of permeability of standard pervious concrete with 10% fines S.No Unit weight of standard pervious concrete (0% fines) after 24 hours (kg/m3) Coefficient of permeability K (cm/sec) 1 1949.76 0.49
  65. 65. 65 4.5.4 Pervious concrete with 10% fly ash as cement replacement Quantities of materials: Cement = 351 kg/m3 Fly ash = 39 kg/m3 Coarse aggregates = 1660 kg/m3 Fine aggregates = 0 kg/m3 Water = 117 litres per CUM Table4.19: unit weight and coefficient of permeability of standard pervious concrete with 10% Fly ash as cement replacement S.No Unit weight of standard pervious concrete (0% fines) after 24 hours (kg/m3) Coefficient of permeability K (cm/sec) 1 1949.76 0.59 4.5.5 Permeability of Pervious concrete with 10% Rice husk ash as cement replacement Quantities of materials: Cement = 351 kg/m3 Rice husk ash = 39 kg/m3 Coarse aggregates = 1660 kg/m3 Fine aggregates = 0 kg/m3 Water = 117 litres per CUM Table4.20: unit weight and coefficient of permeability of standard pervious concrete with 10% rice husk ash as cement replacement S.No Unit weight of standard pervious concrete (0% fines) after 24 hours (kg/m3) Coefficient of permeability K (cm/sec) 1 1949.76 0.53
  66. 66. 66 4.6 COMPARISONS: 4.6.1 Compressive Strength Comparisons: 4.6.1.1 Compressive Strength Comparison of Standard Pervious Concrete and Pervious Concrete with Fine Aggregates: Table4.21: compressive strength of pervious concrete with different quantities of fine aggregate S.No Age of concrete Standard pervious concrete(0% fines), MPa Pervious concrete with 5% fines, MPa Pervious concrete with 6% fines, MPa Pervious concrete with 7% fines, MPa Pervious concrete with 8% fines, MPa Pervious concrete with 9% fines, MPa Pervious concrete with 10% fines, MPa 1 7 16.72 17.36 17.75 18.32 18.98 18.76 18.28 2 14 19.26 19.60 19.73 19.93 21.47 21.23 20.23 3 28 21.06 21.98 22.47 23.79 24.13 23.47 22.87 The above table clearly shows that the compressive strength of pervious concrete increases with increase in age and percentage of fines up to 8%. Beyond this value, the compressive strength starts to decrease. A graph showing the variation in compressive strength of pervious concrete by using the above values by taking percentage fines on x-axis and compressive strength on y-axis for 7,14 and 28 days as shown below.
  67. 67. 67 Figure4.11: Graph of compressive strength of pervious concrete with different quantities of fine aggregates  The 7 days compressive strength of 5% fines pervious concrete is less than the standard pervious concrete with 0% fine aggregates. It may be due slow development of early strength due to mixing  The pervious concrete with 8% fine aggregates gives highest compressive strength beyond which the compressive strength begins to fall. 0 5 10 15 20 25 30 0 5 6 7 8 9 10 CompressivestrengthinMpa Percentage of fines(%) Comparisonof compressive strengthwith different fine aggregatequantities 7 days 14 days 28 days
  68. 68. 68 4.6.1.2 Compressive Strength Comparison of Standard Pervious Concrete and Pervious Concrete with cement replacement: Table 4.22: compressive strength of pervious concrete with cement replacement S.No Days Standard pervious concrete with 0% fines, MPa Pervious concrete with 10% FA as cement replacement, MPa Pervious concrete with 10% RHA as cement replacement, MPa Pervious concrete with 10% FA and RHA as, MPa 1 7 16.72 17.26 19.92 17.79 2 14 19.26 19.92 21.13 20.33 3 28 21.06 22.87 23.93 23.12 FA = Fly Ash RHA = Rice Husk Ash Figure 4.12: Graph of Age of concrete Vs compressive strength value comparisons with the cementitious materials  The pervious concrete with 10% Rice husk ash as cement replacement gives highest value of compressive strength when compared to fly ash replacement and standard pervious concrete.  The pervious concrete with mixture of fly ash and rice husk ash given least value of compressive strength. This may due to non homogeneity between the two cementitious materials. 0 5 10 15 20 25 30 0% Fines 10% Flyash 10% RHA 5% Flyash and 5% RHA Compressivestrength(Mpa) Pervious concrete with different quantities of CMs Compressivestrength comparison 7 days 14 days 28 days
  69. 69. 69 4.6.2 Permeability Comparisons: 4.6.2.1 Comparison of Permeability of Standard Pervious Concrete and Pervious Concrete with Little Amounts of Fine Aggregates: Table 4.23: Co-efficient of permeability of pervious concrete with addition of different quantities of fine aggregates and cementitious materials S.No Standard pervious concrete with 0% fines (cm/sec) Pervious concrete with 8% fine aggregates (cm/sec) Pervious concrete with 10% fine aggregates (cm/sec) Pervious concrete with 10% fly ash as cement replacement (cm/sec) Pervious concrete with 10% rice husk ash as cement replacement (cm/sec) 1. 1.02 0.76 0.49 0.59 0.53 Figure 4.13: Graph of co-efficient of permeability of pervious concrete with addition of different quantities of fine aggregates and cementitious materials  The co-efficient of permeability is maximum of 1.02 cm/sec for standard pervious concrete with 0% fine aggregates and minimum of 0.49 cm/sec for pervious concrete with 10% fine aggregates  The pervious concrete with 10% fly ash has minimum co-efficient of permeability of 0.59 cm/sec and that of rice husk ash is 0.53 cm/sec. The reason for least values of permeability is due to fineness of cementitious materials. 0 0.2 0.4 0.6 0.8 1 1.2 0 fines 8 10 10% Flyash 10% RHA Coefficientof permeability(K)cm/sec) Pervious concrete with different quantities of fines and CMs(%) Co-efficient of permeability coefficient of permeability

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