Potential of Stabilised Composite Mud Block as an Eco Construction Material

Abstract

Present concerns for sustainable development have led to a revival of traditional building practices using natural or recycled resources. There is a perception that the use of earth as a conventional construction material is likely to save manufacturing and transportation cost, time, energy and environmental pollution. Stabilized compressed earth block is an innovative advancement of the traditional earth technology that involves adding a little quantity of stabilizer such as cement to earth and making compressed earth blocks. While available research has focused on performance of typical soils, no research has delved into the structural performance of the several types of soil available in Kenya. Moreover, no research has sought alternative and cheap stabilizers for these soils. In this research, three types of soils available in Kenya (murram, red coffee and black cotton soils) were used. Different percentages of stabilizers such as cow dung, quarry dust, waste paper, plastic fibre, cement and limes were also used. In order to evaluate the different kinds of stabilized earth as sustainable and acceptable construction materials for eco-housing construction in the African subcontinent, this experimental work delved into basic material properties, as well as strength tests on specimens made of blended or composite soils. Tests conducted include Atteberg limit, particle density, particle size distribution, compaction and linear shrinkage test on different soils as well as strength test on composite blocks and walling unit. The percentages of stabilizers used were 4% and 6% for cement, 4%for lime while the soils were blended with sand and quarry dust at varying percentage. Further, this study also involved blending the soil with cow dung, waste paper and plastic polythene fibre at varying ratios as well as alternative compaction method. Result obtained from this study show that murram blocks stabilized with 6% of cement had a satisfactorily higher strength of 4.4MPa which is above the minimum strength required by Kenya standard of 2.5MPa. When an alternative compaction method involving both hand compaction followed by machine compaction was used, the compressive strength of blocksat 28 days increased from 3MPa to 4.3 MPa, from 3.9MPa to 5.2MPa, from 4.4MPa to 6.2MPa for composite black cotton soil, red coffee soil and murram soil respectively. The results obtained further reveal that stabilized black cotton soil blocks blended with 20% cow dung gave a strength of 2Mpa, which is much higher than the strength of unblended black cotton block of 0.6MPa. Furthermore, the results of compressive test on wall panels show that the compressive strength of stabilized compressed earth block wall is higher than the compressive strength of stone blocks wall. It also showed that 40% of the cost of construction materials could be saved when stabilized compressed earth blocks are used as alternative construction materials.