An Investigation on the Compressive Strength of Concrete with Rice Husk Ash as Cement Replacement and Addition of Chemical Admixtures

Rice husk ash (RHA) is a renewable agricultural by-product from rice milling that is abundantly available in rice-producing countries like the Philippines. It has the highest proportion of silica content among all plant residues. This study utilized RHA as a cement replacement with the addition of chemical admixture. An investigation of the influence of RHA and accelerating admixture on the compressive strength of concrete was conducted. A volumetric method concrete mix design was used with a 0.56 water-cement ratio. A 10% RHA partial cement replacement with chemical admixture variations of 0.5, 1.0, 1.5 and 2.0% was utilized. Cylindrical samples measuring 150 x 300 mm were tested for compressive strength at curing ages of 7, 14 and 28 days. The results of the study revealed that the optimum increase of compressive strength of 9.8% against the control concrete mix was achieved when a concrete mix of 10% RHA partial cement replacement was added with 1.5% of admixture. With a compression test result of 2,353 psi, the said mixture could be used for secondary applications such as flooring according to the American Concrete Institute M-15 code and for non-structural concrete such as concrete for sidewalks, borders and filling.