Abstract
The cost of cement has made concrete production expensive such that the housing deficit in developing countries is on the rise despite all the efforts by governments and other stakeholders to produce affordable housing units for the populace. Ashes of agricultural products such as rice husk, known as mineral admixtures may have pozzolanic characteristics which would be more beneficial to the housing industry in terms of strength gain and economy than being pollutants to the environment. Rice Husk Ash (RHA), because of its finely divided form and very high silica content and amorphousness, proved to be useful for strength gain of Rice Husk Ash Concrete (RHAC). Rice husk ash was manufactured by uncontrolled burning, ground, sieved and replaced with cement at 0%, 5%, 10%, 15%, 20% and 25% in mass for the mixes C20, C25, C30 and C35 where their compressive strengths were verified at 3, 7, 14, 21, 28, 56, 90 and 180 days. The X-ray diffraction pattern list indicated amorphous as well as diffused peak of about 8000 counts of SiO2 representing crystalline structures identified as cristobalite. A physical examination of the RHA showed very fine appearance, grey color and specific gravity of 2.06. The chemical analysis also revealed the existence of oxide content to be 55.8% representing 0.78% of Fe2O3, 54% of SiO2 and 1.06% of Al2O3 representing 20.23% lower than the minimum value of 70% required for pozzolans. Generally, the compressive strength values decreased as the RHA content in the mixes increased but when compared to the control concrete the optimum replacement percentage of Ordinary Portland Cement (OPC) with RHA at 5% showed an increase above the control concrete for C20 mix. The increase in the RHA in the mixes resulted in the high demand for water in all the mixes.
Highlights
The use of concrete in infrastructural developments in the world especially in developing countries has taken a center stage as the most expensive building material to be resourced as can be seen in the cost of housing units in Ghana.In spite of this, through the years, governments, private investors and other stakeholders in developing countries have made efforts to provide affordable housing facilities for citizens, but greater populations continue to live in deplorable conditions due to their inability to afford for housing, thereby resulting in their exposure to unhealthy environments and hazard-prone structures [1]
The compressive strength values decreased as the Rice Husk Ash (RHA) content in the mixes increased but when compared to the control concrete the optimum replacement percentage of Ordinary Portland Cement (OPC) with RHA at 5% showed an increase above the control concrete for C20 mix
Rice husk ash has been used in Europe, Asia and the Americas as a partial replacement of cement in concrete to reduce the quantity of cement in concrete as well as improving the compressive strength based on the target strength expected
Summary
The use of concrete in infrastructural developments in the world especially in developing countries has taken a center stage as the most expensive building material to be resourced as can be seen in the cost of housing units in Ghana.In spite of this, through the years, governments, private investors and other stakeholders in developing countries have made efforts to provide affordable housing facilities for citizens, but greater populations continue to live in deplorable conditions due to their inability to afford for housing, thereby resulting in their exposure to unhealthy environments and hazard-prone structures [1]. In line with the objectives of governments and their development partners to improve the standard of living of citizens through the provision of affordable housing facilities, the cost of production of ordinary Portland cement being one of the major factors of the cost of housing units needs to be reduced drastically to make housing affordability the accelerator of economic development to be envisaged. Rice husk ash has been used in Europe, Asia and the Americas as a partial replacement of cement in concrete to reduce the quantity of cement in concrete as well as improving the compressive strength based on the target strength expected. Several studies have been undertaken where ultrafine RHA was used as partial replacement of cement in concrete, as viscous modifying agent in self-compacting concrete, in low-cost sandcrete block production, in determining of its pozzolanic activity [3] as well as environmental and economic benefits being derived from it
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