Optimization of Soil-Lime and Cement Mixes for Compressed Earth Stabilized Blocks for Low-Cost Housing in East Africa (Kenya)

Abstract

The population of East Africa (Kenya) has continued to increase steadily due to rural urban migration. This has created a large population influx of low-income earners which has resulted in lack of low-cost affordable housing. Low-cost housing has always been in short supply and the large urban population has only exacerbated the situation. Furthermore, these economic migrants are poor and look to the governments for assistance in housing. The lack of adaptation of new construction techniques and use of locally available low-cost building materials has made housing to be scarce. Cement is two to three times the cost of construction lime in East Africa, thus the need to maximize the use of lime. Conventional building materials (fired bricks and concrete blocks) have proved to be expensive and unsustainable; stabilized earth is the cheapest of the materials locally available. There is a huge incentive to investigate the use of sustainable and appropriate technologies that are affordable in local communities. This study research project looks at enhancing the use of soil-cement normally used for compressed stabilized earth blocks (CSEBs) with the addition of lime. Also investigated is the relationship between soil properties, stabilizers (lime & cement). Areas considered are: • Proportions between soil and stabilizer will be optimized taking into consideration the specific characteristics of soil. • The use of lime and cement in a two-stage mixing process; reduce the shrink swell of high Plasticity Index (PI) soils by reducing the PI with lime (cure for 24 hrs.). Then provide strength with cement to ensure blocks are dense and durable with regular surfaces and edges. Phase 1 testing revealed improvements in the samples dry and wet compressive strength, abrasive strength and capillary absorption, compared to the control soil-cement sample. Phase 2 testing entailed further mix design optimization of the samples with the highest properties tested in phase 1 by reducing the cementitious (lime and cement) materials used in the mix designs.