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Hemp and lime as a building material copy


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Hemp and lime as a building material copy

  1. 1. Hemp and Lime as a Building Material Dinesh.
  2. 2. Contents:-  Introduction  Historical back ground  Hemp  Lime  Composite materials  Combination of hemp and lime  The three mixes  Method of sample preparation  Laboratary tests  conclusions
  3. 3. Introduction:- The combination of hemp and lime is considered as an alternate structural building to other conventional materials. These materials are ‘environmentally friendly’ and have, overall, a low level of embodied energy. Hemp is a plant and thus utilizes carbon dioxide during its growth. Natural hydraulic lime produces less co2 in its production than cement and also absorbs co2 as it sets.
  4. 4. Historical background The first documented use of organic materials in construction dates back as the Mesopotamian civilization(2000 Bc), where buildings were discovered made from mud bricks reinforced with reeds. This tradition has continued through the ages and is now being revitalized in the in the 21st century through the increased building with cob (monolithic mud and straw), straw-bale houses and adobe(mud and straw bricks).
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  6. 6. Hemp  There is much interest among both engineers and architects in using hemp hurds as an aggregate with hydraulic lime binders, as they are both strong and light.  Throughout the world, hemp is cultivated commercially for its strong, valuable fibers and oil  These hurds are natural by-product after the plant has been used for other purposes.  Hemp plant does not require pesticides and requires less fertilizing.  One hectare of hemp produces 3.5 tons of hurds.
  7. 7. Lime  Lime comes from lime stone rock and has been used in building for thousands of years.  It was used in ancient times and in the roman empire.  The earliest traces of lime use in construction have been found in early Egyptian buildings  The blocks of pyramids, were bond using a lime motor.
  8. 8. The dome of the pantheon is made of lime concrete
  9. 9. Composite materials  A composite building material consists of at least two different materials, neither of which is suitable for constricting buildings on its own but when combined, result in a strong and suitable material.  These materials have been used in buildings for thousands of years. Adobe mud huts made from a mixture of straw and clay have existed since the stone age.  In the last 40 years polymer composite materials have been developed.
  10. 10. Glass fiber mats and natural fiber like hemp fibers are the good composite mix inner car door made of hemp fibers
  11. 11. Combination of hemp and Lime  Hemp hurds can be used as an aggregate in the lime mix to form a durable and lightweight material  Currently, this is being used as an infill in timber frame houses Infill of timber frame structure with hemp hurds and lime
  12. 12. The three mixes 1) Hemp and lime 2) Hemp fibers (and hurds) and lime 3) Hemp, lime and sand volume proportions of materials in mix Hemp hurds: lime hemp fibers (and hurds):lime hemp hurds: lime: sand 0:1 0:1 3:1:0 1:1 1:1 3:1:1 2;1 2:1 3:1:2 3:1 3:1 3:1:3 4:1 no samples 3:1:4 5:1 5:1 no samples
  13. 13. • Three cubes and three cylinders were prepared so that an average strength could be calculated for each mix  The bulk density of each material was calculated bulk density of material Hemp hurds hemp fibers(and hurds):lime Lime sand 92 kg/m3 106 kg/m3 636kg/m3 1027kg/m3
  14. 14. Method of sample preparation  The dimensions of cubes used were 100mmx100mmx100mm. The cylinders had a diameter of 100mm and were 200mm high. The moulds are lined with a cling film.  A known volume of lime was mixed with water until a workable state was reached. This water/lime ratio was kept constant during the experiments. To prevent hemp from absorbing water during mixing, hemp hurds was soaked in water for 10minutes in advance. Mould lined with cling- film
  15. 15. • The materials were added gradually to a mixture. Slump test was carried out, for mixes with a slump less than 40mm a 2.5kg proctor hammer used for compacting.  The samples were de-moulded after 24 hours and allowed to dry at room temperature. They are then placed in a carbonation tank with a concentration=10%. They are allowed to cure for 30 days.  Lime sets firstly with water and secondly with co2. The use of carbonation tank accelerated this process, as the normal combination of co2 in air is 0.03%
  16. 16. A test was conducted for the samples to know how much lime reacted with co2. The samples were sprayed with phenolphthalein after testing. The purple colour in photos shows phenolphthalein reacted with the un-carbonated region.
  17. 17. Laboratory tests  The compressive and tensile material strength of the different mixes was measured using cube compression tests.  The cubes did not fracture but deformed slowly due to the fibrous nature of the material. This displacement was limited to 10mm, and the maximum force was recorded
  18. 18. Determination of young's moduli for various mixes Mix hurds[mpa] mix fibers[mpa] mix sand[mpa] 1:1 167 1:1 219 3:1:0 38 2:1 78 2:1 67 3:1:1 89 3:1 38 3:1 68 3:1:2 162 4:1 36 - - 3:1:3 77 5:1 24 5:1 22 3:1:4 38
  19. 19. Results of tensile tests for mixes Hurd lime mix Hurd mix density[kg/m3] force[kn] tensile strength[n/m3] 1:1 1269.27 10.44 0.22 2:1 1094.23 10.70 0.23 3:1 865.57 7.10 0.15 4:1 714.17 5.75 0.12 5:1 652.33 5.68 0.12 Fiber lime mix Mix density[kg/m3] force[kn] tensile strength[n/m3] 1:1 1331.90 11.98 0.25 2:1 1118.00 8.66 0.18 3:1 914.47 6.43 0.14
  20. 20. Hurd/lime/sand mix mix density[kg/m3] force[kn] tensile strength[n/mm2] 3:1:1 1274.60 5.64 0.12 3:1:2 1708.83 7.82 0.17 3:1:3 1878.40 8.21 0.17 3:1:4 1877.37 4.71 0.10 Advantages of hemp and lime as building material:-  Low embodied energy –an ‘environmentally friendly’ material.  A structural and insulating building material.  Durable and light weight.  Provides a ‘breathable’ and porous building membrane. This prevents moisture build-up and ensures a dry building.
  21. 21. conclusions  Building with this material uses less energy than conventional methods and is a sustainable building solution for the future.  It is a material which both insulates and provides structural strength.  A 5:1hurd/lime mix was considered to be as optimum mix ratio with a compressive strength of 0.7N/mm2 and an estimated thermal conductivity of 0.11w/mk.  A 3:1 hurd/lime mix has the same strength as 5:1hurd/lime mix. This is a significant result as previously hurd/lime mixes used as infill in timber frames have been based on 3:1 mix by volume which uses the lime binder less efficiently and has a higher thermal conductivity.
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