Investigating the suitability of using natural pozzolana(volcanic ash) activated by lime as a stabilizer on the strength of soft clay blocks for low-cost construction

Abstract

Adequate housing is considered one of the basic human rights. However, due to cost limitations, many people lack access to adequate housing and decent shelter. Construction materials constitute a significant component of the cost and Portland cement is one of the costly materials used in present-day construction. Soft clay blocks are common masonry units for construction of buildings all over Uganda both in heated and unheated form especially in rural areas. Un-stabilized soft clay blocks have low compressive and flexural strengths, and high-water absorption rates therefore prone to failure in masonry at loads lower than the stabilized soft clay blocks in addition to first deterioration rates when subjected to dump conditions and storms. The high cost of cement which is the traditional stabilizing agent, and its greenhouse effect on the environment has led to the use of alternative building materials in the production of blocks and bricks. This study seeked to investigate the suitability of using Natural Pozzolana and lime on the engineering properties of soft clay blocks i.e., Compressive strength and Water Absorption. Soft clay blocks of size 210 × 110 × 100 mm were prepared with natural pozzolana in percentages of 5, 10 and 20% by weight of soil and hydrated lime in percentages of 4,8 and 10% by weight of soil. The Mud blocks were prepared using the manual hand mixing method and cured. The blocks, after 7, 14, 21 and 28 days of curing were tested for compressive strength and water absorption. It was found that as the natural pozzolana and lime increased, there was a reduction in the water absorption of the stabilized soft clay blocks over the unstabilized blocks. The water absorption reduced from 12.2% at 5% Natural pozzolana and 4% Lime to 7.8% at 20% Natural pozzolana and 10%Lime after 28days compared to the unstabilized mud blocks with water absorption of 15.9% after 28 days. On the other hand, the compressive strength increased from 2.2MPa at 5% Natural pozzolana and 4% Lime to 2.9MPa at 20% VA and 10%Lime after 28 days compared to the unstabilized mud blocks with 1.6MPa after 28 days. Therefore, the study concludes that the inclusion of the natural pozzolana and Lime generally improved the properties of the soft clay blocks, and therefore recommended it for use in the building of low-cost houses.