Optimizing Compressive Strength Characteristics of Hollow Building Blocks from Granite Quarry Dust and Sand
As a result of the overdependence on river-sand for construction activities, there is need to source for a readily available material with comparable strength when used for certain purposes (in this case, sandcrete hollow blocks). This paper evaluates the compressive strength of sandcrete hollow building blocks when its sand fraction is partially replaced with quarry dust. A range of 0%, 10%, 15%, 20% and 25% sand replacement with quarry dust was used in the cement: sand mix ratios of 1:6 and 1:8 for molding the blocks of size 450mm x 225mm x 225mm.These blocks were produced by machine compaction under a pressure of 3N/mm2. Results indicate that for mix ratio of 1:6 at 28 days when 10% quarry dust partial replacement was applied, the compressive strength of the blocks was about 7% greater than that of blocks without partial replacement. Also, for the mix ratio of 1:8 at 28 days and 10% partial replacement with quarry dust, the compressive strength of the blocks was about 46% higher than that without partial replacement of the sand fraction. The strength of the blocks increases with increase in quarry dust partial replacement of sand. However, for the mix ratios employed, it is noted that 15% partial replacement of sand with quarry dust gave an optimum compressive strength of 3.8N/mm2 and 4N/mm2for the two mix ratios respectively. It is suggested therefore, that the optimum replacement of sand with granite quarry dust as fine aggregates should be 15% of the sand fraction in hollow building blocks of the size and mix ratio adopted herein.