Dynamically-compacted cement stabilised soil blocks for low-cost walling

This document contains the detailed results and conclusions of work carried out during a PhD to investigate the processing, production and performance of dynamically compacted cement-stabilised soil blocks suitable for sustainable low-cost building. An earlier project carried out by the author demonstrated that full-size blocks could be manufactured by dynamic compaction. It was hoped that this technique could be applied to the self-evident need for low-cost housing in the humid tropics. The apparent advantages of this process, over quasi-static compression (slow steady squeezing), have led to further investigation into the critical factors influencing the production of such building units. Initial tests on small cylindrical samples produced by both quasi-static compression and dynamic compaction provided a means of comparison and helped to develop relationships between dominant variables. These tests showed that the moisture content of the compact was a critical variable, influencing its consolidation and its final cured strength. Optimisation studies were undertaken to determine acceptable parameters for impactor mass, drop height and number of applied blows. These chosen parameters were then extrapolated to full-size block production with the necessary adjustments for practicality and cost. Full-size block production using the Test Rig indicated similar relationships as those discovered at the smaller scale, including the more effective consolidation offered by dynamic compaction. From this experience a production prototype was designed and disseminated to a collaborator in India for further trials and feasibility studies. These trials demonstrated that dynamic compaction could produce blocks with a 7-day wet compressive strength of between 3-5MPa with only 5% cement, (typical building regulations require block strength greater than 3.5MPa after 28-days). Feasibility studies there indicate dynamic compaction offers potential savings of 40% compared with local high-tech CSSB manufacture.

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