Performance of acid leached rice husk ash as cement replacement material

Teng, Kar Ing (2024) Performance of acid leached rice husk ash as cement replacement material. Final Year Project, UTAR.

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Abstract

This study investigated the impact of acid on rice husk ash and the performance of acid leached rice husk ash (RHA) as a replacement of cement. The main objective of this study was to test the reactivity of rice husk ash (RHA) leached with different types of acids and the mechanical properties of mortar when mixed with rice husk ash (RHA) that leached by acids. Hydrochloric acid (HCL), sulfuric acid (H2SO4), and nitric acid (NHO3) were used as leaching agent, with two leaching times such as 30 hours and 36 hours. The RHA that leached by different acids and times were tested by x-ray diffraction test (XRD) and particle size analysis test (PSA). Mortars with different RHA contents such as 0%, 5%, and 10% were also prepared and tested for compressive strength and water absorption. The results of the study showed that the RHA that leached by acid can reduce the amount of crystalline silica and the smallest particle size was obtained in RHA that leached by hydrochloric acid for 36 hours. It was found that RHA with the smallest particle size can improve the compressive strength of mortar, where mortar containing 5% RHA has the highest compressive strength compared to mortar containing 10% RHA. It was also found that mortar containing 10% RHA leads to increased water absorption with reduced strength. It was also found that the addition of RHA in mortar mixtures leads to decreased workability. When the proportion of RHA in mortar increase, workability decrease. Based on the results, it is recommended to use acid leaching of RH to reduce crystalline silica and suggest hydrochloric acid to leach RH to obtain the smallest particles, because amorphous silica and small particles can enhance pozzolanic reaction. It was also found that leaching RHA for 36 hours is more effective than 30 hours. The proportion of RHA leached with hydrochloric acid to replace cement in mortar should be 5% as it can maximize the compressive strength while reducing water absorption. Further research is needed to investigate the effect of other acid types and the long-term durability of mortar mixtures with RHA as cement replacement materials in different environments. In addition, the use of other additives or adjustment of the water-cement ratio should be investigated to optimize the workability of mortar mixture that mixed with RHA. Keywords: Acid, Rice husk ash, Cement replacement, Mortar, X-ray diffraction, Particle size, Durability, Workability, Compressive strength

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