Structural Response of Interlocking Stabilized Laterite Soil Block Panels for Single Storey Housing

Abstract

The right to housing in Kenya has led to increasing demand for adequate and affordable housing units. The use of interlocking stabilised soil blocks (ISSB) is one of the technologies used to meet the shortage. The ISSB is a technology that encourages utilization of locally available building materials for walling structures. The performance of un-reinforced interlocking block masonry walls made using CINVA-Ram blocks subjected to static compression loads was investigated. Since masonry structures are mainly subjected to compressive stresses, the stress-strain relationship of ISSB masonry was used to model its behaviour and develop empirical formulae for predicting the compressive strength. Further, the social acceptability of ISSB technology in Kenyan construction industry was also determined through a survey design. In a laboratory study, Pozzolanic cement (PC), lime (L), rice husk ash (RHA) and cow dung (CD) were used to stabilize soil. Two types of soils: laterite soil with sandy clay loam texture (25% clay and 75% sand), and plasticity index (PI) of 12.09% and clay soil with 5.0 coefficient of uniformity were used. The stabilized blocks were used to make six types of walls of size 900 mm long x 1200 mm high. A finite element analysis adopting the Rankine failure criterion was performed using Abaqus software to simulate the deformability behaviour of the wall which was validated through experimental tests. The predictive empirical formulae for the compressive strength of the ISSB masonry was developed by performing statistical multiple regression analysis. The social acceptability of the ISSB technology was carried out through use of semi-structured interviews on two target groups: technology users and non-technology users. The collected data was analysed by use of thematic analysis. The experimental results indicated that block compressive strength, water absorption and durability (1-min abrasion test) were within the recommended levels at the optimum stabilizer percentages. It was found that lime stabilization causes a delayed gain of compressive strength in soils with higher clay content as compared to pozzolanic cement. However, for lime to perform better in clay soil stabilization it should be used together with pozzolanic cement. The wall failure modes were characterized by either diagonal cracking of individual blocks or spalling of block debris. The performance of interlocking block walls in load capacity can be divided into three parts: (1) slow closure of gaps, (2) rapid load uptake, and (3) wall failure. Through finite element modelling, contribution of stress distribution to the wall mode of failure was depicted. In addition to the mechanical properties of masonry, the FE simulation results indicated that the deformability behaviour of ISSB masonry is influenced by the type of stabilizer used on the target material. This dictates the stress distribution and vertical displacement of the masonry. The interview results found that the technology is most useful in the construction of residential houses, perimeter fencing walls and partition walls. Perceived low performance and inadequate demonstration projects amongst non-users limited their willingness to use the ISSB technology. Desirable features of the ISSB technology include: aesthetic value, ease of construction and non-use of mortar. The study recommends a combined system of constructing columns and ISSB masonry. Furthermore, clear design standards containing workmanship and construction guidelines must be provided to members of the construction industry.