Design, modelling and optimisation of an interlocking stabilised soil block (issb) making machine for improved performance

Abstract

In Zambia it is estimated that the existing housing stock stands at 2.5 million units catering for about 16 million people. The national housing deficit stands at more than 2 million houses and is compounded by urbanisation. Efforts have so far been made to use alternative building technology called Interlocking Stabilised Soil Block (ISSB) technology. Currently, two manually operated compressing machines IBM-M1 and IBM-M2 have been developed by Technology Development and Advisory Unit (TDAU) of the University of Zambia (UNZA). However, the machines have challenges of low productivity and compressive strength which does not conform to the standards governing the performance of interlocking soil blocks. According to tests the two machines IBM-M1 and IBM-M2 machines have production rates of 232 and 283 blocks per eight-hour shift respectively which are by far lower than the 2200 blocks as produced by motorised machines. Compressive strength test was performed and the resultant mean failure loads for both machines were 3.9 MPa and 2.9 MPa respectively which is below the international standards of 6 to 7 MPa for compressed stabilised soil blocks. In view of this shortfall a hydraulically operated ISSB machine (IBM-H1) was designed and fabricated and the machine production capacity improved by 239.22%. The mean block strength also improved significantly to 7 MPa and 6 MPa from 3.9 MPa and 2.9 MPa using 25% and 12% respectively of Portland cement content. This study has drawn the conclusion that ISSB making machine production rate is affected by the mould loading rate, soil compression and block ejection time. Furthermore, the strength of ISSB blocks increases linearly as the block bulk density and the stabiliser quantity increases. Key words: Interlocking Stabilised Soil Block (ISSB), Technology Development and Advisory Unit (TDAU), Interlocking Block Maker-Manual 1 (IBM-M1), Interlocking Block Maker-Manual 2 (IBM-M2), Compressive strength.