Hemp Crete 1p455t

HEMPCRETE

SEMINAR PRESENTATION BY PRAJITH K P REG NO 15010602 GUIDED BY Sri EBIN JOE SYRIAC

Dept of Civil Engineering GOVT POLYTECHNIC COLLEGE, PALAKKAD

INTRODUCTION 

Hemp (Cannabis sativa) is an agricultural crop that can be used as a building material in combination with lime and cement.

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A composite building material that combines a cementitious binder (building limes and cement) with hemp shives, the woody core of the hemp stalk is generally referred to as hemp concrete (HC).

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HC has many advantages as a building material but it is not load-bearing and must be used in combination with a loadbearing RCC frame.

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The aim of this seminar was to evaluate the feasibility of using both hemp shives and fibres in a HC to determine an optimal mix of the different binding agents and to investigate if adding cement binder would improve mechanical strength of the material.

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The effects on compressive strength of pre-mixing the binder or creating perforations in the test specimens were also investigated.

INTRODUCTION 

Hempcrete is a lightweight concrete, made from hemp pulp (or shiv), and hydraulic or aerated lime.

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It is typically used for timber frame infill, roofing tiles, insulation, renders, and floor slabs. Hempcrete can make up for its mechanical drawbacks through functionality and environmental benefits. For instance, hempcrete exhibits a low thermal conductivity (λ= 0.1–0.2 W/m·K) that regulates the temperature and humidity levels within a dwelling, a high acoustic performance when compared to traditional concretes, and an exceptional resistance to fire without the need for fire-preventative measures

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ECO EFFICIENCY AND HEMPCRETE Specific criteria for eco-efficiency entails the following characteristics 

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Sustainability of the material: This entails the use of Life Cycle Analysis to determine the durability of the material. In addition, we include how it affects the decrease in consumption of natural resources. Reduction of Pollutants: Non-biodegradable and toxic waste production, emission of greenhouse gases, and water contamination is to be objectively avoided. Retention of economic value: Regarding the use of sustainable building materials, the goal of engineering remains the same in regard to the efficient and practical implementation of services.

ECO EFFICIENCY AND HEMPCRETE In light of this, eco-efficiency can have a more hands-on application in the form of an eco-material, or rather, a material that exhibits the qualities of eco-efficiency.

This definition sets the context for the use of hempcrete, which is to be defined as an eco-material. A picture of a hempcrete block is shown in Figure.

APPLICATION OF HEMPCRETE 

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In the construction phase, hempcrete is most commonly used for a timber frame infill, which is built using a removable formwork mold, such as a plastic casing. The hempcrete is poured between the two formwork plates into a dismountable mold. Each layer is carefully leveled when placed in the mold, around 20 cm in thickness for each addition. This infill consists of a density at 400 kg/m3, and a thermal conductivity (λ) of 0.1 W/m.K, at 0% RH. Alternatively, hemp can be applied as roofing insulation with a density of 200-250 kg/m3 (λ=.06 W/ (m.K), at 0% RH), as well as a floor application, where the density becomes 500 kg/m3 (λ=0.12 W/(m.K) at 0% RH). The walling and roofing applications must meet a

VAPOR PERMEABILITY  Hempcrete is a highly breathable material, which allows for the regulation of indoor temperature and humidity.  As the physical states of water (which has a heat conductivity of λ=0.6 W/m.K) alternate from liquid to vapor, it will actually modify the specific heat and thermal conductivity of hempcrete (normally λ= 0.1 W/m.K).  This works to regulate the indoor temperature, reducing the need for heating and cooling systems, in addition to lending the material greater insulation capacity, while maintaining the quality of the air.

ACOUSTIC ABSORPTION Figure 2.2 compares the NRC of hempcrete to several common materials used in houses.

DRAWBACKS TO THE USE OF HEMPCRETE MECHANICAL DRAWBACKS The most significant setback of hempcrete is its poor mechanical performance, which prevents hemp from being used as a loadbearing material. This is due primarily to the fact that hempcrete is highly porous, causing a poor adhesion to the lime binder that results in an elastic-like behavior

Flexural stress of hemp/rHDPE composite at various fiber fraction along with pure Rhdpe

DRAWBACKS TO THE USE OF HEMPCRETE WATER RETENTION  In addition to poor mechanical performance, hempcrete also has a high capacity to absorb and retain water. it can be a significant detriment to its use as a construction material.  For instance, the hemp shiv is able to absorb up to 300-400 times its weight in water problem comes when hempcrete undergoes water absorption for an elongated amount of time without proper ventilation.  When this occurs, the possibility of bio-decay arises, in addition to freezing and thawing issues, and the formation of salt crystals, which all decrease durability.

HEMPCRETE AS A SUSTAINABLE BUILDING MATERIAL  Hempcrete is a bio-composite mix made up of hemp shive, lime, cement and water  It has low density, good thermal and acoustic insulation properties, and can ively regulate humidity in a built environment  However it also has low compressive strength and modulus of elasticity.  Thus hempcrete cannot be used as a direct load bearing material but can used as an infill material in timber stud walls.

Hempcrete Block

OBJECTIVES AND METHODOLOGY OBJECTIVES The aim is to investigate the potential of producing local hemp masonry blocks, using traditional mixes and local raw material.  Study the physical properties of Hempcrete a) Specific gravity of Hempcrete b) Fire resistance of Hempcrete c) Water absorption Identify mechanical properties of hemp concretes using hemp shives and binder compositions. d) Compressive Strength e) Split tensile Strength Investigate whether pre-mixing the binding agents with water before adding it to the hemp affects the final strength of the material.

OBJECTIVES AND METHODOLOGY METHODOLOGY The following steps were involved in implementation of the project and are not limited to, • Collection of raw materials • Mix design • Casting and cubing of Cubes, Cylinders. • Testing of Hempcrete • Discussions and conclusions on the results obtained

MIX DESIGN Hempcrete was moulded for 3 different types of samples. The samples were mixed at different mix ratios. The mix ratios are given at Table 7.1.The 1st sample was moulded with low water ratio.2nd sample was moulded with high water ratio.OPC was added in 3rd sample.

MIX DESIGN  The hemp fibre is chopped up to the length of 5 cm.It must constitute 62% of shives, 35% of fibres and dust particles must not be more than 3%.  The fibre must be kept in water for 24 hours, in order to absorb water.  The lime used can be of Class C, which is commonly used for whitewashing purpose.  The lime has to be powdered and lumps must be avoided.  When lime reacts with water heat is evolved which leads in evaporation of water.  Therefore, the water required is very high as compared to cement.  Also considering that the hemp absorbs more water, the water-binder ratio for the three samples are 100%, 120% and 120 % respectively

MIX DESIGN Sample 1 Quantity Of Materials For Sample 1

MIX DESIGN Sample 2 Quantity Of Materials For Sample 2

MIX DESIGN Sample 3 Quantity Of Materials For Sample 3

MIX DESIGN Moulding into cube

OBSERVATIONS AND DISCUSSIONS

COMPRESSIVE STRENGTH The test method covers determination of compressive strength of cubic hempcrete specimens. It consists of applying a compressive axial load to molded cubes at a rate which is within a prescribed range until failure occurs. The compressive strength is calculated by dividing the maximum load attained during the test by the cross sectional area of the specimen.   APPARATUS: Weights and weighing device. Tools and containers for mixing. Tamper (square in cross section) Testing machine Three cubes (150 mm side)

OBSERVATIONS AND DISCUSSIONS

COMPRESSIVE STRENGTH Compressive strength for different samples at 45 days

OBSERVATIONS AND DISCUSSIONS

COMPRESSIVE STRENGTH Compressive strength for different samples at 60 days

OBSERVATIONS AND DISCUSSIONS

COMPRESSIVE STRENGTH RESULT   The average compressive of Hempcrete is found to be 0.973 MPa and 1.113 for 45 and 60 days respectively. The strength of sample 3, which also constituted OPC was found to be higher than other samples.   INFERENCE   The compressive strength of hempcrete is 1/20 to that of cement concrete. It is also found that the strength of concrete improves if cement is

OBSERVATIONS AND DISCUSSIONS

SPILT TENSILE STRENGTH This method covers the determination of the splitting tensile strength of Cylindrical hempcrete specimens.   Apparatus: • Weights and weighing device. • Tools, containers and pans for carrying materials & mixing. • A circular cross-sectional rod (φl6mm & 600mm length). • Testing machine. • Three cylinders (φ150mm & 300mm in height).

OBSERVATIONS AND DISCUSSIONS

SPILT TENSILE STRENGTH After split tensile test

OBSERVATIONS AND DISCUSSIONS

SPILT TENSILE STRENGTH Split tensile Strength @ 45 days

OBSERVATIONS AND DISCUSSIONS

SPILT TENSILE STRENGTH Split tensile Strength @ 60 days

OBSERVATIONS AND DISCUSSIONS

SPILT TENSILE STRENGTH Split tensile strength

OBSERVATIONS AND DISCUSSIONS

SPECIFIC GRAVITY OF HEMPCRETE Volume of hempcrete block = 150X150X150 = 0.003375

Therefore, the specific gravity of hempcrete was found to be 0.817 which is lesser than that of water. This property of hempcrete makes it floatable in water

CONCLUSION 

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Hempcrete has very low compressive strength and elastic modulus which does not make it suitable as a direct load bearing structural material. Compressive of hempcrete increases with time. These particles can absorb water and hinder in the hydration process of the binding materials and thus result in a lower strength Another important property of hempcrete observed from the compression tests was the large deformation it can undergo after reaching the ultimate load . This shows hempcrete has a quasi-ductile behaviour unlike the sudden brittle failure associated with concrete It was also found that the density is affected by water content of the sample. For higher water content the density decreases due to volume of voids. But this has a good impact on compressive strength. As strength is more for less density.