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1. INTRODUCTION
Our society is now concerned with global warming and carbon emissions. So,
we civil engineers proposing green buildings, zero carbon buildings etc. The
“Hempcrete” can be used to built buildings better than this. This building material has
been prepared from the ecological plant „hemp‟.
1.1 HISTORY
Hempcrete is an ecological and economic building material. It was first
conceived by an imaginative builder and inventor by the name Charles Rassetti
whilst working on a medieval house in a town called Norgent sur Seine in N.W.
France. Within a few years it had become apparent to many people working
around him that this was a product of enormous potential and soon there were
several varieties of Hempcrete being promoted and used in France. Later, Steve
Allin has enthusiastically pioneered the use of hemp in building for the last 14
years and is the author of “Building with Hemp” 2005. He was a director of
Hemp Ireland Ltd. (1998-2003) which was set up to research the possibility of
hemp processing in Ireland. He was now a leading expert in the field, with a
wide knowledge of the growing, processing and utilization of hemp for
construction. In 2009 he founded the International Hemp Building Association,
which has over 100 members throughout the world. He is now working as a
Hemp Building consultant internationally and developing training courses for
Hemp Building techniques and travelling around the world spreading the
knowledge.

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1.2 WHAT IS HEMPCRETE?
Hempcrete is a mixture of hemp hurds (shives) and lime (possibly
including natural hydraulic lime, sand, pozzolans or cement) used as a material
for construction and insulation. Hemp-lime or „Hempcrete‟ is the broad, generic
title for a multitude of mixes containing (as a minimum) a lime based binder and
the inner woody core of the hemp plant. The materials are mixed with water and
this then sets to form a solid mass. The resulting mix has characteristics
depending on the particular constituents, their grading, and the relative ratios of
the constituents in a mix and the method of application.
We are all familiar with concrete and the great variability of properties
and applications it can be put to. Hempcrete shares this variability and hence it is
vitally important that the appropriate material is specified to ensure that the
required properties and performance will be realized. In addition to the material
properties, the detailing within a construction is equally important. When these
two aspects are both appropriate, there can be certainty of a durable
performance.

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2. HEMP
2.1 INTRODUCTION
Hemp is one of the faster growing biomasses known, producing up to 25
tonnes of dry matter per hectare per year. Hemp is very environmentally friendly
as it requires few pesticides and no herbicides. It has been called a carbon-
negative raw material. Hemp is one of the earliest domesticated plants known.
The world leading producer of hemp is China and also legally grown in Spain,
Japan, Korea, France, North Africa, Ireland etc and Europe, Chile and North
Korea in small scale. While more hemp is exported to the United States than to
any other country, the United States Government does not consistently
distinguish between marijuana and the non-psychoactive Cannabis (scientific
name) used for industrial and commercial purposes.
As a new alternative crop for farmers hemp as a crop, offers many
things. The speed at which it grows to heights of 2 metres or more and the dense
canopy it produces keeps competing unwanted plants suppressed and shades the
ground beneath. Its input cost is low as it needs low level fertilizer.
Figure 2.1 Sectional view of the plant

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Also the roots left behind in the ground after harvesting are long and
tough, preventing erosion and providing aeration to the soil once the crop is
removed. The hemp stem comprises an outer skin called bast, which, like jute
contains long fibres, and a woody core, which is most interested in Hempcrete.
The combination of these woody chips or Hurds as they age called with a
„breathing‟ binder can create a material we can build walls with and use as an
infill in roofs and floors.
2.2 USES
Figure 2.2 shows roughly the wide variety uses of the plant hemp:
Hemp is used for a wide variety of purposes including the manufacture
of cordage of varying tensile strength, durable clothing and nutritional products.
The bast fibers can be used in 100% hemp products, but are commonly blended

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with other organic fibers such as flax, cotton or silk, for apparel and furnishings,
most commonly at a 55%/45% hemp/cotton blend. The inner two fibers of hemp
are more woody and are more often used in non-woven items and other
industrial applications, such as mulch, animal bedding and litter. The oil from
the fruits ("seeds") oxidizes (commonly, though inaccurately, called "drying") to
become solid on exposure to air, similar to linseed oil, and is sometimes used in
the manufacture of oil-based paints, in creams as a moisturizing agent, for
cooking, and in plastics. Hemp seeds have been used in bird seed mix as well.
Hempseed is also used as a fishing bait.
Figure 2.3 Hemp stem showing fibers.
The fiber is the most valuable parts of the hemp plant, which refers to
that grow on the outside of the woody interior of the plant's stalk, and under the
outermost part (the bark). Bast fibers give the plant's strength. Hemp fibers can
be between approximately 0.91 m (3 ft) and 4.6 m (15 ft) long, running the
length of the plant. Depending on the processing used to remove the fiber from
the stem, the hemp may naturally be creamy white, brown, gray, black or green.
Hemp has been used to make paper but the paper industry has switched
over to wood pulp. It was often used to make sail canvas, and the word canvas
derives from cannabis. Abaca, or "Manila hemp", a relative of the banana plant,
replaced its use for rope. Burlap, made from jute, took over the sacking market.

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The carpet industry switched over to wool, sisal, and jute, then nylon. Netting
and webbing applications were taken over by cotton and synthetics. Hemp is still
a traditional choice for seals in water plumbing, but is competing with Teflon
and other synthetic materials. Hemp can be used as a "mop crop" to clear
impurities out of wastewater, such as sewage effluent, excessive phosphorus
from chicken litter, or other unwanted substances or chemicals.
2.3 CULTIVATION
Hemp is usually planted between March and May in the northern
hemisphere, between September and November in the southern hemisphere.It
matures in about three to four months.The seeds are sown from mid April to mid
May with grain drills to 4–6 cm sowing depth. Organic fertilizers such as
manure can utilize industrial hemp well. Neither weeds nor crop protection
measures are necessary.
Figure 2.4 hemp plant

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2.4 HARVESTING
Smallholder plots are usually harvested by hand. The plants are cut at 2
to 3 cm above the soil and left on the ground to dry. Mechanical harvesting is
now common, using specially adapted cutter-binders or simpler cutters. The cut
hemp is laid in swathes to dry for up to four days.
Figure 2.5 Industrial hempseed harvesting machine in France.
Figure 2.6 Hemp harvesting by Hand

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3. HOW HEMPCRETE IS FORMED?
As explained above, Hempcrete is mixture of hemp hurds and lime products as
binding material. The hemp is harvested and let to dry in sunshade. Then it is baled and
brought to the factory. With the help of the machines it is processed to separate the
fibers and hurds (shives). These hemp shives when mixed with hydraulic lime products
to form Hempcrete.
Figure 3.1 Hemp shives
3.1 TRADEMARKED VARIATIONS
There are a number of trademarked variations for hempcrete. Here are some
of them:
3.1.1 HEMCRETE
Hemcrete, or Tradical Hemcrete, is a trademarked version of hempcrete
produced by Lime Technology in the UK.

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3.1.2 CANOBIOTE
Canobiote consists of hemp hurds coated with mineral salts. Canobiote is
intended to provide insulation for wood-framed, closed lofts and floors. It‟s
particularly ideal for those that receive regular use. Canobiote was patented by a
group called La Chanvriere de L‟Aube (LCDA). LCDA is a French company
that specializes in production and processing of industrial hemp. Established in
1973, LCDA works together with many hemp farmers located in Champagne -
the vineyard region in Eastern France.
3.1.3 CANOSMOSE
Also patented by LCDA, Canosmose is a light-weight concrete made
with hemp hurds and natural lime. Canosmose is intended for non-load bearing
masonry, such as walls sectioned with wooden supports.
3.1.4 ISOCHANVRE
Isochanvre was created by France Périer, who previously worked for
LCDA promoting Canobiote. Like Canobiote, Isochanvre is typically used for
acoustic and thermal insulation. It is also increasingly being used as a
construction material.
3.2 THE DIFFERENCE?
These products appear to be quite similar. Isochanvre and Canobiote are slanted
towards insulation, while Canosmose and Hemcrete are promoted as a construction
material. Hempcrete is self insulating. It‟s resistant to rotting, mice, rodents, etc. It is
also fireproof, waterproof, and weather resistant. Hempcrete actually has some pretty
cool benefits over concrete too.
From the above Hemcrete or Tradical Hemcrete is most commonly used.
Tradical Hemcrete is based on a UK produced formulated lime binder (Tradical HB)
and UK grown hemp shive (Tradical HF).

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3.3 TRADICAL HEMCRETE
Tradical Hempcrete has been available in France for many years and has
also been used for many important high profile projects in the UK. Tradical Hemcrete
is an insulation material that works in conjunction with a structural frame (normally
timber) to provide a wall build system. Generally it is only used on the external
envelope walls where the highest thermal insulation standards are required. The
thickness of the wall determines the design insulation value of the wall, with thicker
walls providing better insulation values however they can take significantly longer to
dry thoroughly. Cured and dried Tradical Hemcrete is a Vapour-Permeable (Breathable
or Vapour-Open) material that as a minimum must be able to easily pass moisture to the
external atmosphere and preferably also through the internal face of the wall. This can
also be used in roof applications and has excellent characteristics to prevent summer
overheating.
3.3.1 COMPOSITION
3.3.1.1 Tradical HB.
Tradical HB is a formulated lime made in the UK by Lime Technology
under licence from Lhoist UK and based on many years research and testing by
the Lhoist Group. The Lhoist Group is the largest lime manufacturers in the
world and Tradical HB has been specially developed to use with hemp.
3.3.1.2 Tradical HF
Tradical HF is made from UK grown hemp, processed in the UK by
Hemp Technology under an ISO-9001 regime.
3.3.2 FEATURES
Lime Technology has developed standard building systems for use with
Tradical Hemcrete. These building systems are approved by LABC (Local Authority
Building Control).

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3.3.2.1 Product
Tradical Hemcrete is a, robust, highly breathable and sustainable
insulation, which can be cast or sprayed. It is a blend of specially selected and
chopped woody core (shive) of industrial hemp and lime based formulated
binder that is in powder form.
3.3.2.2 Suitable uses and Benefits
It can be used for the creation of walls, and used in roof and wall
construction with excellent thermal and breathable, creating healthy living and
working environments. It is a lightweight material that achieves a negative
carbon footprint as it locks up approximately 130kg of CO² per m3 of wall and
when protected by Limetec lime renders and plasters, provides one of the best
value walling systems for high thermal mass, good insulation, breathable,
sustainable and commercially viable construction. It reduces cost and
construction time. It provides some racking strength for the frame and as a result
the frame may not need additional bracing. The high thermal performance and
air-tightness avoids the need for cavity wall construction. The ability of the
walls to breathe and to store heat allows for passive self regulation of the
temperature and humidity within the building, often reducing the need for
heating and air conditioning. It is easy to use and can be formed to almost any
castable shape. It has good synergy with other natural breathable building
products. It has good fire resistance and e effective thermal inertia delivering
temperature change buffering.
3.3.2.3 Manufacture and Packaging
Radical HB is a special lime binder based on hydrated air lime blended
with selected cementitious, hydraulic and inorganic materials. This ensures the
perfect particle size distribution and setting characteristics to create the binder
for use with Tradical HF Hemp. Tradical HB Lime Binder is manufactured to
BS EN 459 (part 1) and packed in water resistant paper containing 22kg (48 per
pallet) per bag to facilitate mixing.

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Tradical HF is a hemp aggregate made from the inner woody core of the
hemp plant‟s stem. The hemp is chopped, graded and de‐dusted to give a natural,
sound and breathable product. It is cultivated in the UK without agrochemicals
and is harvested annually. The hemp is a renewable primary material; the
industrial processing is mechanical and requires little energy or toxic products. It
is packed in recyclable polymer bales of 200 ltr (36 per pallet) capacity to
facilitate mixing.
3.3.2.4 Storage
Keep dry and protected particularly the binder. Once the protective
cover has been removed, pallets should be protected. Do not store pallets more
than two high.
3.3.2.5 Quality Assurance
The product constantly undergoes in-house monitoring, using tested and
certificated quality management systems conforming to the current international
standard EN ISO 9001 and the environment standard EN ISO 14001.
3.3.2.6 Mix Ratio
Tradical Hemcrete is specified as three product densities,
• Standard 275
• Hi Strength 330
• Hi Insulation 220.
The higher the density the stronger the Tradical Hemcrete mix, the higher the
thermal mass (thermal capacity) and the lower the insulation value. The thermal
inertia (diffusivity or resistance to temperature change) remains approximately
the same for all mixes. Tradical Hemcrete Standard 275 is the most commonly
used mix that provides an excellent combination of insulation, thermal mass and
thermal inertia. Some technical data of this mix are:

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• Nominal Dried Density of 275kg/ m³
• Thermal conductivity: λ=0.06W/m.K
• μ Vapour Diffusion Resistance: 4.84
• Heat Capacity: 1500 – 1700 J/kg
• Air Permeability: 0.75 gm/m²/mm hg
• Vapor permeability: 24.2 gm/m²/mm hg
The binder mix ratios are usually specified as follows:
Table: 3.1 STANDARD MIX RATIOS OF HEMCRETE
MIX TRADICAL
TO HEMP
RATIO
THERMAL
CONDUCTIVITY
(W/m.K)
APPLICATION
STANDARD 275 3:2 0.06 Timber frame on
inner wall with direct
fix breathable wall
panel
HIGH
STRENGTH 330
2:1 0.07 Timber frame centred
to wall thickness with
Tradical Hemcrete on
both sides of the
framing
HIGH
STRENGTH 220
1:1 0.05 Floor and roof infill
3.3.2.7 Training
Lime Technology offers full training support to customers using Tradical
Hemcrete. Contractors are training in a two stage process (theory and practical)
and are required to pass the test. Beyond this they implement a checking
procedure to completed works as well as advice to main contractors for
subsequent and on-going works when the specialist installer has completed
works.

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3.3.2.8 Testing
Tradical Hemcrete has been independently tested for fire performance,
racking strength and other key parameters.
3.3.2.9 Cost
Tradical Hemcrete can produce high performance walls that compete on
price with conventional construction techniques.
3.3.2.10 Performance
Casting is a straight forward method of use and can be readily achieved
with good tradesman following training by Lime Technology Ltd. Spraying
requires bespoke equipment and trained operatives, or members of the Sprayed
Concrete. A typical 300mm Tradical Hemcrete wall provides a U value of 0.19.
1m3 of Tradical HB & HF mix will cover approximately 3.3m2 of walls.
3.3.2.11 Timber structure
The timber frame should be designed to support the load from the upper
floors and roof by a qualified Structural Engineer. A typical timber frame could
use 38mm x 89mm studs at 600mm centres for two storey domestic
construction. Other types of frame such as lightweight steel frame may also be
used, please consult Lime Technology‟s technical department for details.
3.3.2.12 Finishes
Only use Baumit breathable lime renders with the Tradical Hemcrete
Insulation Wall System to ensure performance and maintain the product
warranty. Other finishes that can be considered such as timber cladding, tile and
slate hanging or brick or stone facing, laid in Limetec Hydraulic Lime Mortar.

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4. DESIGN AND CONSTRUCTION
The hempcrete buildings are constructed according to the design procedure
given by Lime technology. This type of building is not yet constructed in India so only
an American standard code has been used by them. The following are the design
guidance given by the Lime technology Ltd for domestic scale external walls and timber
structures (version 1-2010).
4.1 DESIGN GUIDANCE
4.1.1 AXIAL COMPRESSION
Tradical Hemcrete will provide restraint to the timber studs against
buckling in the line of the wall. Other than this the study is designed to BS 5268
as for traditional timber framed construction. Horizontal noggins between the
studs are not required to reduce the stud effective length due to its continuous
restraint by the Tradical Hemcrete.
Restraint from the Tradical Hemcrete cannot be assumed across the wall.
4.1.2 LATERAL BENDING FROM WIND LOAD
Tradical Hemcrete will contribute to the lateral load capacity of the wall
panel under wind loading. The structural properties of Tradical Hemcrete such
as flexural strength are not fully established yet. A conservative approach for the
design of Tradical Hemcrete needs to be adopted at this stage. Work carried out
to date shows that Tradical Hemcrete will resist a wind load of at least
0.15kN/m² in panels 2.4m high. Further research is being carried out which is
expected to conclude that higher lateral loads can be resisted. Revised loads will
be included in an update of this design guide following the completion of the
research.
The remainder of the wind load above 0.15kN/m2
is to be taken by the timber
studs.

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4.1.3 RACKING FOR WIND
For a conventional timber frame design it is usual to provide studs on the
Inside face of the wall and sheath these externally to resist racking. For Tradical
Hemcrete walls the sheathing is on the inside face of the studs and acts as
permanent shuttering. There are other benefits of the board such as only skim
plastering being required and it providing a good substrate for internal fixtures.
The recommended 9mm Multi-Pro XS board has been tested for racking
resistance in conjunction with timber studs only (no Tradical Hemcrete) and has
shown satisfactory results.
Testing of Tradical Hemcrete alone to resist racking has also been undertaken
and has shown satisfactory results so Tradical Hemcrete alone is adequate to
resist normal racking loads without any contribution from an inner board. On
this basis it would be possible to omit the inner boarding altogether and cast the
Tradical Hemcrete against a temporary shutter. Temporary/permanent bracing
may be required to keep the structure braced until the Tradical Hemcrete sets. A
separate internal finish would then be needed.
4.1.4 WINDOW AND DOOR OPENINGS
Cripple studs will be needed to be designed to carry the concentration of
wind and vertical loads at the reveal of window and door openings in the usual
manner. Lateral restraint to the cripple studs cannot be assumed at openings as
the Tradical Hemcrete is on one side only.
4.1.5 SHRINKAGE OF TRADICAL HEMCRETE AND TIMBER FRAME
Tradical Hemcrete shrinks around the same amount as timber in the
direction of the grain but only around 10% of the shrinkage across the grain.
This means that there is little differential shrinkage between the timber studs and
the Tradical Hemcrete, but differential shrinkage of around 5mm can occur at
the floor zone if solid softwood floor joists are used; which could lead to
cracking in the finishes. It is therefore a requirement that engineered floor joists
are used at this location to limit the effects of shrinkage

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4.2 CONSRTUCTION
Tradical Hemcrete to be cast between temporary or permanent shuttering
or by spraying method and installed by a trained/competent contractor.
Thickness: Standard Tradical Hemcrete wall: between 250 and 400mm plus
finishes.
Density: Standard mix cast to a nominal density of 275 kg/m3 (ratio of 2 no.
Tradical HF to 3 no. Tradical HB).
Framing Structural frame on the internal face of the wall, designed by Project
Engineer or Timber Frame designer in accordance with Lime Technology Ltd‟s
„Timber Frame Design Guidance‟. Any metal brackets/strapping etc in direct
contact with Tradical Hemcrete to be either Stainless Steel or paint protected
galvanized.
4.2.1 TEMPORARY SHUTTERING
4.2.1.1 General
The procedure for this type is simple. Place the shuttering on the both
sides and fill the mixed hempcrete in between and compacted by simply
tamping.
Formwork: Temporary shuttering can be hired subject to availability on request
from Lime Technology Ltd or any other form of light weight shuttering can be
used. Leave temporary shuttering in place for at least 24 hours; provide support
to lintel sections for 2 weeks. Increase these timescales in cold weather
conditions. Leave Tradical Hemcrete for 6-8 weeks (min.) during the summer
months and 8-12 weeks (min.) during the winter months to dry following site
management guidance provided by Lime Technology Ltd, before any finishes
are applied.
External finish: Two coat system to be applied only when Tradical Hemcrete is
suitably dry. Prime any exposed timber or ply with 5mm MC55W bonding
adhesive and allow to cure at 1 day/mm.
Basecoat: Baumit Fibrous Lightweight Render FL68 10mm thick with
200 x 300mm strips of Baumit AG01 mesh applied diagonally across the corners

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of all openings and other stress points, followed by a further 5mm (total
thickness 15mm) of FL68 applied wet on wet. Rule off and grid-float (lattice
plane) within 24 hours. It is essential that this is undertaken and then to wait 1
day/mm of thickness before applying any finish to the basecoat.
Topcoat: Baumit SEP 02 textured finish in standard colours – other
finishes available - please discuss specification and application with Lime
Technology Ltd.
Internal finish: Onto 9mm Multi Pro XS LT: All joints must be taped and
boards sealed appropriately at board junctions. Use either: -
Lime finishes: 1mm primer of Baumit MC55W with a Baumit KG30
smooth finish applied at 2-3mm thick once priming coat has dried.
Gypsum finishes: 2-3mm British Gypsum Durafinish. Breathable
emulsion paint finish applied internally as required.
4.2.1.2 Working Constraints
General: Do not use frozen, water damaged or out of date materials or apply
Tradical Hemcrete to frozen or frost affected backgrounds.
External work: Halt the installation of Tradical Hemcrete when air temperature
is at or below 5°C and falling and do not resume installation until air
temperature is at 3°C and rising. Adequate waterproof but breathable covering
required to protect insitu Tradical Hemcrete when either air temperature is
below freezing or when precipitation is expected. Protection required to Tradical
Hemcrete until external finishes have been applied.
Internal work: Take all necessary precautions to enable internal work to proceed
without damage when air temperature is below 3°C.

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Figure 4.1 Temporary shuttered hempcrete walls
4.2.2 PERMANENT SHUTTERING
The method is same as in temporary shuttering. The only difference is
that the shuttering placed at one end is permanently placed for support. Usually
wooden panels or plywood are used as permanent supports. Recommended
permanent shuttering to internal face 9mm Multi Pro XS LT board attached to
the structural timber stud frame using stainless steel fixings. The rendering
process is done in the same way as in the temporary shuttering.

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4.2.3 SPRAYING METHOD
This is the easier method but is little costlier. Permanently shuttering
technique is used here. In this method the hempcrete mix is placed in spraying
machine. Then it is sprayed to the permanent shuttered panels up to the desired
thickness and with the pressure of spraying it is compacted. The rendering is
done in the same manner as that of the above methods.
Figure 4.2 Spraying hempcrete Mix using Machine

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5. PROPERTIES OF HEMPCRETE
 Thermal mass Insulation
 Negative Carbon
 Low Density
 Clean Air
 High Thermal Resistance (R-Value = 2.5 - 3.0 per inch)
 High Thermal Inertia
 Vapor Permeable (breathable)
 Design Flexibility (adjustable thickness)
 Fire and Pest Resistant (NO Termites)
 Significantly Reduce Co2 Emissions
 Inherently Airtight
 No Waste
 No Mold
 No Termites
 No Dry Rot
 Natural Substrates for Plasters and Renders
 Low Air Infiltration
 Zero Land Fill at end of life

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6. ADVANTAGES OF HEMPCRETE
 Hemp transforms CO2 during its growth by capturing carbon and releasing
oxygen. Using Hemp in construction locks up the captured carbon for the life of
the building. Approximately 110kg of CO2 is locked away per cubic metre of
Hempcrete.
 Hempcrete is highly insulating with very low U values, resulting in an energy
efficient building, ideal for meeting today's higher building standards.
 Hempcrete is a way of providing thermal mass. This means that hempcrete
buildings will change temperature more slowly and reduce heating loads
compared with lighter weight building materials with similar U values.
 Hempcrete can be sourced from within the UK using renewable UK grown
hemp.
 Hempcrete is natural and vapor permeable (or "breathable"), helping to facilitate
healthier buildings.
 Hemp can be grown in rotation with food crops to improve the soil and reduce
weeds, it does not require agrochemicals in its cultivation and there is no need
for pesticides or insecticides. The Hemp shive used in Hempcrete is a low-
value waste product of the hemp fiber producing industry.

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7. CONCLUSION
Hempcrete is a light weight material and is better than concrete. It is 7 times
stronger than concrete. The Hemcrete buildings are better than green buildings and zero
energy buildings. Studies have shown that, for each square meter of house walling, up
to 200 kilograms of carbon dioxide is emitted from its construction. This works out to
be around 40 tons of carbon dioxide emitted for a typical house. Hempcrete, on the
other hand, can actually remove carbon dioxide from the air, and trap it within the wall
construction. The producers of Tradical Hemcrete claim that it has been found to lock
up around 110 kilograms of carbon dioxide per m3
. Thus, it reduces the threat of global
warming. The product should install in India as the climatic conditions our nation needs
this type of materials. And also the plant has a wide variety of uses thus improving the
agricultural field of our nation.

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8. REFERENCE
1. M S Shetty (1994), Concrete Technology, Laxmi Publications
2. Steve Allin (2012), “ Hemp - A really ecological building material for India”. Energy
BLITZ, A Bi- monthly energy & environment magazine, New Delhi, Vol-I (IV), pg 10-
12