Lect 7 pavement materials

Road Building Materials:
Materials, Testings, Properties
Analysis

MANAGEMENT OF INFRASTRUCTURE
AND COMMUNITY DEVELOPMENT

What will you learn?
 Basically you will learn about types and
characteristics of road building materials, its
testings, mix design method of asphalt for asphalt
pavement, and green road materials

MANAGEMENT OF INFRASTRUCTURE AND COMMUNITY DEVELOPMENT

What competency do you want to expect?
 Knowledge competency: You will recognize types
and characteristics of road building materials, its
testings, and mix design method of asphalt for
asphalt pavement.
 Skill competency: you are able to bridge
communication between community and
engineering service provider (road
planner/designer/contractor) in regards with
selecting appropriate materials for building road


Contents
 Subgrade/soil
 Aggregates
 Asphalt and asphalt mixture
 Portland cement concrete


Soil/subgrade
The soil investigation provides pertinent information about
soil and rock for decisions related to the following:
 selection of road alignment;

 the need for subgrade or embankment foundation
treatment;
 investigation of slope stability in cuts and
embankments;
 location and design of ditches and culverts;

 selection and design of road pavement;

 location and evaluation of suitable borrow and
construction materials;
 design of foundations for bridges and other structures.


Effect of poor design subgrade


Preliminary soil investigation
 An early phase of the soil investigation encompasses
collection and examination of all existing information. This
may include the identification of soil types from topographic
maps, geological maps, soil maps, aerial photos, and satellite
images, registration of groundwater conditions, and
examination of existing road cuttings.
 The visual examination may be coupled with a small amount
of sampling and testing.
 The preliminary soil investigation will help to secure a broad
understanding of soil conditions and associated engineering
problems that may be encountered.


Topographic map
 Most countries in the world are covered by
topographic maps on the scale of 1: 50,000 to 1:
250,000.
 These maps may be used as an aid to geological
interpretation, to identify drainage networks, and to
estimate gradients and earthworks volume.
 However, topographic maps may be inaccurate,
and they are often out of date.


Geological map
 Most countries are covered by national geological
maps of scale 1: 100,000 or smaller. More detailed
mapping may exist, but few developing or emerging
countries have large-scale maps.
 Geological maps normally depict the bedrock up to
the level beneath the soil. In some cases, rock
types can be correlated with particular soil types
but, for the road engineer, the main use of
geological maps is for planning and for providing
background information for the interpretation of
aerial photos.


Soil maps
 Soil maps are mainly produced for agricultural
purposes, but only limited areas in developing and
emerging countries are covered. Engineering
particulars cannot be read from agricultural soil
maps, but they are useful for planning purposes,
because they indicate where variations in the soil
types can be expected.


Detailed soil investigation
 The detailed soil investigations may be divided into
field investigations and laboratory testing. The field
investigations include geophysical explorations, test
pits and borings, sampling of soils and rocks,
registration of soil profiles, and measurements of
groundwater levels. Laboratory testing includes
testing of representative samples


Geophysical methods as field soil investigation for
road
 Two geophysical methods of soil exploration are used for road
purposes. These are the electrical resistivity and the seismic
refraction methods
 The electrical resistivity method makes use of the varying
electrical resistivity of different soils. The resistivity depends
mainly on the content of clay minerals, moisture content, and
the type and concentration of electrolyte in the soil–water. An
increasing content of clay, water, or electrolyte causes
decreasing resistivity. In performing the test, four electrodes
are inserted in the surface of the soil and arranged on line
symmetrical about a point


Geophysical methods as field soil investigation for
road (continued)
 The seismic refraction method relies on the principle that the
velocity of sound in soils and rocks is different for different
materials. A shock wave is created by detonation of a small
explosive charge on the surface of the terrain. The time taken
for the shock wave to reach detectors placed on a line at
different distances from the source are recorded. Providing
the soil is uniform to some depth, these time intervals are
directly proportional to the distance from the point of
detonation. If the sound velocity in a substratum is higher than
in the overburden, then the time interval to more distant points
is shortened because the shock wave travels through the
substratum for some of the distance. By plotting travel time
against distance from the point of detonation, the depth to the
substratum can be calculated. The seismic refraction method
is particularly useful in predicting the depth to bedrock.


Laboratory soil testing
 Particle-size distribution
 Moisture content
 Specific gravity
 Atteberg limits
 Plasticity
 Free swell
 Density
 Compaction
 California bearing ratio
 Dynamic cone penetrometer
 Soil classification


Particle-size distribution
 The distribution of particle sizes in soils is important
in road engineering since the value of many
properties, such as internal friction, voids content,
wear resistance, and permeability, depend on the
gradation. The distribution of particle sizes larger
than 75m is determined by sieving a sample
through a number of standard sieves


Test devices


Analysis
 The results of a sieve analysis are normally
displayed in a graph. The sieve seizes are plotted
on a logarithmic scale as the abscissa. The
proportions, by mass, of the soil sample passing the
corresponding sieves are plotted on an arithmetic
scale as the ordinate.
 A well-graded soil is one with a gently sloping sieve
curve, indicating that the soil contains a wide range
of particle sizes.
 A uniformly graded soil is one with predominance of
single sized particles.
 A gap-graded soil has one size range of particles
missing.


Soil gradation curve


Coefficient of uniformity and Coeff. Of
Curvature
 The coefficient of uniformity is sometimes used as a
single numerical expression of particle-size
distribution for purposes of succinct communication.
The coefficient is defined as the ratio of the sieve
size through which 60 per cent of the material
passes to that of the sieve size through which 10
per cent passes.



 The coefficient of curvature is factor describing
shape of gradation


D10

Effective Size = D10 10
percent of the sample is
finer than this size


D30 and D60


Well graded requirements


Well graded sand?


Atteberg limits


Water content and specific gravity
 The engineering properties of a soil, such as the strength
and deformation characteristics, depend to a very large
degree on the amount of voids and water in the soil. The
moisture content is defined as the mass of water
contained in a soil sample compared with the oven-dry
mass of the sample. It is customarily expressed as a
percentage, although the decimal fraction is used in most
computations.
 The specific gravity of a soil is used in the equations
expressing the phase relation of air, water, and solids in a
given volume of material. The specific gravity of a soil is
calculated as the ratio between mass and volume of the
solid particles of a sample. The volume of the particles is
determined by placing the sample in a volumetric bottle
(pycnometer) filled with water and measuring the volume
of displaced water.


Atteberg test device


Plasticity
 The plasticity limits are used to estimate the engineering
behaviour of clayey soils and form an integral part of several
engineering classification systems.
 The plasticity limits include the liquid limit (LL) and the plastic
limit (PL), and they are determined by arbitrary tests on the fine
soil fraction passing the 42m sieve.
 The LL is determined by performing trials in which a sample is
spread in a metal cup and divided in two by a grooving tool. The
LL is defined as the moisture content of the soil that allows the
divided sample to flow together, when the cup is dropped 25
times on to a hard rubber base.
 The PL is determined by alternately pressing together and
rolling a small portion of soil into a thin thread causing
reduction of the moisture content. The PL is defined as the
moisture content of the soil when the thread crumbles.
 The difference between the LL and the PL is called the plasticity
index (PI).


Free swell
 Expansive clays are a problem in many regions in
the tropics.
 A simple test can be used to verify swelling
tendencies. A measured volume of dry, pulverized
soil is poured into a graduated glass containing
water. After the soil comes to rest at the bottom of
the cylinder, the expanded volume is measured.
The free swell is calculated as the increase of
volume as a percentage of the initial volume.


Density
 The field density (in-place density) has a great
influence on the bearing capacity and the potential
for settlement. Soil compaction is therefore an
important component of road construction because
it increases the density. Measurements of field
density are made during soil investigation, but most
measurements are taken to assist with compaction
control during construction.


Sand cone
 The sand cone or sand replacement method is
widely used to determine the density of compacted
soils.
 A sample is removed by hand excavation of a hole
in the soil. The in situ volume of the sample is then
determined by measuring the volume of dry, free-
flowing sand necessary to fill the hole. A special
cone is used to pour the sand into the hole. The dry
mass of the sample is determined in the laboratory.
The method is not recommended for soils that are
soft, friable or in a saturated condition. The method
is rather time-consuming


Sand cone


Compaction
 The level of compaction to be achieved in the field
during construction is normally specified as a
percentage of the maximum dry density obtained in
a compaction test in the laboratory. The traditional
laboratory tests are the „standard‟ and the „modified‟
AASHTO compaction or the „light‟ and „heavy‟
British Standard (BS) compaction. They are also
known as standard and modified „proctor tests‟ after
the person who invented the laboratory compaction
tests.


Compaction


Example


California bearing ratio
 The California bearing ratio (CBR) test is the
most common test for evaluating the
bearing capacity of subgrade soils.
 It measures the force needed to cause a
plunger to penetrate 2.5 or 5mm into a soil
sample compacted into a 2-litre cylindrical
mould with a diameter of 150 mm.
 The measured force is taken as a
percentage of a standard force.


Laboratory CBR equipment


CBR value
 It is the ratio of force per unit area required to
penetrate a soil mass with standard circular piston
at the rate of 1.25 mm/min. to that required for the
corresponding penetration of a standard material.
 The C.B.R. values are usually calculated for
penetration of 2.5 mm and 5 mm. Generally the
C.B.R. value at 2.5 mm will be greater that at 5 mm
and in such a case/the former shall be taken as
C.B.R. for design purpose. If C.B.R. for 5 mm
exceeds that for 2.5 mm, the test should be
repeated. If identical results follow, the C.B.R.
corresponding to 5 mm penetration should be taken
for design.


CBR value
 C.B.R. = (Test load/Standard load) * 100

Penetration of Standard load
plunger (mm) (kg)
2.5 1370
5 2055
7.5 2630
10.0 3180
12.5 3600


CBR Curve


Quick estimation of CBR


Dynamic cone penetrometer
 The dynamic cone penetrometer (DCP) is a quick
and cheap alternative to in situ CBR tests. A 30o
steel cone is forced into the soil by use of a drop
hammer, and the penetration is measured in
millimetres per blow. Empirical relations between
penetration and CBR may be derived


Exercise: what the unified soil classification
system?


Range of
CBR values
by soil
types


Exercise: what is AASHTO classification?


Aggregates
 Mineral aggregates make up 90 to 95% of a HMA
mix by weight or approximately 75 to 85% by
volume. Their physical characteristics are
responsible for providing a strong aggregate
structure to resist deformation due to repeated load
applications.
 Aggregate is defined as “a granular material of
mineral composition such as sand, gravel, shell,
slag, or crushed stone, used with cementing
medium to form mortars or concrete or alone as in
base courses, railroad ballasts, etc.”
 These aggregates can be divided into three main
categories natural, processed, and synthetic
(artificial) aggregates.

Natural aggregates
 Natural aggregates are mined from river or glacial
deposits. They are frequently referred to as pit- or
bank-run materials. Gravel and sand are examples
of natural aggregates. Gravel is normally defined as
aggregates passing the 3 in. (75 mm) sieve and
retained on the No. 4 (4.75 mm) sieve. Sand is
usually defined as aggregate passing the No. 4
sieve with the silt and clay fraction passing the No.
200 (0.075 mm) sieve. These aggregates in their
natural form tend to be smooth and round.


Processed aggregates
 Processed materials include gravel or stones that
have been crushed, washed, screened, or
otherwise treated to enhance the performance of
HMAC. Processed materials tend to be more
angular and better graded.


Synthetic aggregates
 Synthetic aggregates are not mined or quarried.
Rather, they are manufactured through the
application of physical and/or chemical processes
as either a principal product or a by-product. They
are often used to improve the skid resistance of
HMAC. Blast furnace slag, lightweight expanded
clay, shale or slate are examples of synthetic
aggregates


Testing of aggregates: Particle size
analysis
 Particle size analysis on aggregates is carried out using
the same procedure as described for soils. Circular
sieves with a frame diameter of 200mm are normally used
for analysis of soils and fine aggregate. However, for
analysis of coarse aggregate it is useful to employ sieves
with a frame diameter of 300 mm or more, because bigger
samples are needed to obtain representative results. An
important use of the sieve curve is for estimating the
volume occupied by different fractions of the soil.
 In some types of natural gravel, particularly laterite, there
may be a significant difference between the specific
gravity of the coarse and the fine particles. For these
types of soils, it may be useful to convert mass
proportions to volume proportions when plotting the
sieve curve


Testing of aggregates: Specific gravity
 The specific gravity of aggregates is used for
converting mass to volume. Volume calculations of
aggregates are primarily used in connection with
mix design for cement and asphaltic concrete. The
test procedure is similar to that described for soils,
except that bigger samples and bigger pycnometers
are needed for coarse aggregate. Instead of using
a volumetric bottle, the volume of the sample may
be determined by placing the sample in a wire
basket and weighing it before and after immersing
in water.


Specific aggregates equipment kits


Water absorption
 High porosity of aggregates may be a sign of low
mechanical strength. Furthermore, aggregates with
high porosity may be difficult and costly to dry
during processing of asphalt hot mix. The porosity
is estimated by measuring the water absorption.
This is determined by immersing a dry sample in
water for 24h. The surfaces of the particles are then
dried by rolling the sample gently in a dry cloth. The
water absorption is calculated as the difference in
mass between the saturated, surface-dry sample
and the dry sample as a percentage of the mass of
the dry sample


Sand equivalent test
 The sand equivalent test is useful for evaluating the
plastic properties of the sand fraction of aggregates.
A volume of damp aggregate passing the 4.75mm
sieve is measured. The material should not be dried
before testing as this may change its properties.
The sample and a quantity of flocculating (calcium
chloride) solution are poured into a graduated glass
and agitated. After a prescribed sedimentation
period, the height of sand and the height of
flocculated clay are determined.
 The sand equivalent (SE) is the height of sand as a
percentage of the total height of sand and
flocculated clay in the glass.


CBR test
 The CBR test is unsuitable for testing of crushed
stone and coarse gravel, because of the need for
removing particles bigger than 20mm. For design
purposes, the CBR is sometimes estimated based,
not on testing, but on previous experience
combined with evaluation of the shape of the
particle-size distribution curve


Particle shape
 The particle shape influences the compaction and strength
characteristics of aggregate mixtures. Cubic particles are less
workable but more stable than flaky and elongated particles.
The particle shape test is performed on coarse particles, for
example, particles retained on the 6mm sieve. Each particle is
measured using a length gauge. Particles with a smallest
dimension less than 0.6 of their mean size are classified as
„flaky‟. Particles with a largest dimension more than 1.8 times
their mean size are classified as „elongated‟. The mean size is
defined as the mean of the two sieve sizes between which the
particle is retained in a sieve analysis. The percentage by
mass of flaky particles in a sample is called the „flakiness
index‟.


Soundness
 The soundness test is used as part of the materials
survey and design process to estimate the
soundness of aggregate when subjected to
weathering. The test subjects samples to repeated
immersion in saturated solutions of sodium or
magnesium sulphate, followed by drying. The
internal expansive force, derived from the
rehydration of the salt upon re-immersion,
simulates the weathering action. The sample is
sieved before and after the test, and the percentage
of loss for each fraction is calculated.
 The precision of the test is poor, and it is not usually
considered for outright rejection of aggregates
without confirmation by other tests


Field density
 Field density tests are used in construction to
evaluate the compaction achieved in aggregate
base and sub-base. Common methods are sand
cone and nuclear density gauge, as described
earlier. However, measurements of field density are
not very precise when dealing with coarse material.
In some countries, this has led to the use of
method-specifications for compaction instead of
end-product specifications


Los Angeles abrasion test
 The los angeles abrasion test gives an indication of
the resistance to abrasion in combination with the
impact strength of coarse aggregates. The test is
used for selecting the most suitable aggregate
sources for quarrying. A sample is loaded together
with a number of steel balls into a steel drum, which
revolves on a horizontal axis. The los angeles
abrasion value is the percentages of fines passing
the 1.7 mm sieve after a specified number of
revolutions of the drum.


Higher water absorption, poorer abrasion resistance


Affinity for bitumen/asphalt
 Different test methods exist for determining the
resistance to stripping, that is, the separation of a
bitumen film from the aggregate resulting from the
action of water.
 However, none of the methods are very reliable. In
the simplest method, the resistance to stripping is
determined by immersing an uncompacted sample
of bitumencoated aggregate in water. At the end of
a soaking period, the percentage of surface


Asphalt
 Asphalt pavements consist of selected mineral
aggregates bound together by a bituminous binder.
 Asphalt layer is used as different asphalt pavement
types, ranging from thin surface dressings to thick
layers of asphalt concrete.


Bituminous binders
 Bitumen or asphalt cement is a black to dark brown
sticky material, composed principally of high
molecular-weight hydrocarbons.
 It can be found as a component of natural rock
asphalt, but most bitumen is derived from the
distillation of crude oil.


Basic Characteristics of Bitumen
 Bitumen is a thermoplastic material that gradually
softens, and eventually liquefies when heated.
Bitumen is characterized by its consistency at
certain temperatures.
 Traditionally, the consistency is measured by a
penetration test, a softening point test and a
viscosity test.


Asphalt Cement Specifications and Tests


Bitumen Tests
 Penetration test. Penetration is the number of units of 0.1 mm
penetration depth achieved during the penetration test


 Softening points test


Ductility test
 Ductility is the number of centimeters a standard briquette of
asphalt cement will stretch before breaking


Flash point
 Flash point is the temperature to which asphalt cement may
be heated without the danger of causing an instantaneous
flash in the presence of an open flame


Solubility test
 Solubility is the percentage of an asphalt cement
sample that will dissolve in trichloroethylene. In this
procedure, an asphalt cement sample is dissolved
in trichloroethylene and then filtered through a
glass-fiber pad where the weight of the insoluble
material is measured. The solubility is calculated by
dividing the weight of the dissolved portion by the
total weight of the asphalt cement sample. This test
is used to check for contamination in asphalt
cement. Most specifications require a minimum of
99% solubility in trichloroethylene


Bitumen grade
 Bitumen is available commercially in several
standard grades. In many countries, the grades are
based on the penetration value. The grade is
usually expressed in a penetration value bracket,
for example, 80–100. The British Standard (BS)
specifies 10 different grades ranging from pen 15 to
pen 450. Earlier standards in the United States
specified five types, with pen 40–50 as the hardest
and pen 200–300 as the softest. In Indonesia used
bitumen has penetration grade 60-80.


Volumetric Properties of Asphalt Mixtures


Mass – volume relationship diagram


Solution


Portland cemen concretet (PCC)
 PCC is composed of cement paste and aggregates.
The cement paste consists of Portland cement
mixed with water while the aggregates are
composed of fine and coarse fractions.


Portland cement


Portland cement
 Portland cement is composed of approximately 60
to 65% lime (CaO), 20 to 25% silica (SiO2), and 7
to 12% iron oxide (Fe2O3) and alumina (Al2O3).
The percentages of the different components may
be varied to meet different physical and chemical
requirements based on its intended use


Aggregate
 Particle size distribution can be further divided into coarse-
aggregate and fine aggregate grading. The particle size and
distribution has an impact on the workability of the mix. In
general, the larger the maximum particle size, the less Portland
cement is necessary. Particle shape and surface texture have a
greater impact on the properties of fresh concrete than they do
on the properties of hardened concrete. The rougher and more
angular the particles are, the more water is required to produce
workable concrete. However, rougher and more angular
particles tend to have a stronger bond with the cement and
water mixture. Voids between aggregates also increase with
increased aggregate angularity. Specific gravity is not generally
considered a measure of aggregate quality, but is required in
the mix design process. Absorption and surface moisture are
used to determine the aggregate’s appetite for moisture and its
current moisture condition. The results of these tests are used
to control concrete batch weights


Water, chemical admixtures
 Almost all naturally occurring water that is safe for
drinking should be suitable for making PCC.
 Chemical admixtures may be used to enhance
Portland cement properties based on the
requirements for a specific application. The primary
reasons for using admixtures are to reduce the cost
of concrete construction, to enhance certain
concrete properties, and to ensure the quality of
concrete during the different stages of construction.


 Water-reducing admixtures are used to reduce the quantity of
mixing water required to produce concrete of a specific slump,
reduce the water– cement ratio, or increase slump. Regular
water reducers may decrease the water content by 5 to 10%.
High-range water reducers (also called Superplasticizers) may
decrease the water content by 12 to 30%. While high-range
water reducers are typically more effective than regular water
reducers, they are more expensive. Water reducers typically
produce an increase in strength because of the reduction in
the water– cement ratio. The effectiveness of water reducers
is dependent on its chemical composition, concrete
temperature, cement composition, cement fineness, cement
content, and the presence of other admixtures. The
effectiveness of water reducersdiminishes with time after it is
introduced into the batch.


 Retarding admixtures are used to slow down the
rate at which concrete sets. Retarders may be used
tocomp ensate for accelerated setting due to hot
weather or delay initial set for prolonged concrete
placements. The presence of retarders may reduce
early (first few days) strength gain. Accelerating
admixtures have the opposite effect from retarding
admixtures in that they increase early strength gain.
 However, the use of accelerating admixtures may
lead to increase in drying shrinkage, potential
reinforcement corrosion, discoloration, and scaling.


 Fly ash, ground granulated blast-furnace slag, and
condensed silica fume are commonly used mineral
admixtures.


Finely divided mineral admixtures
Finely divided mineral admixtures are powdered or
pulverized materials added to PCC to enhance the
properties of fresh and/or hardened concrete. They
may be broadly put into four categories:
 Cementitious materials,

 Pozzolanic materials,

 Pozzolanic and cementitious materials,

 Inert materials.


Lect 7 pavement materials

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Lect 7 pavement materials