Effects of Silica in Rice Husk Ash (RHA) in producing High Strength Concrete

High strength concrete (HSC) are known to have a higher amount of cement binder in the mix design properties with low w/b ratio. The high mass of cement content produced substantial heat liberation in the concrete due to the reaction between cement and water, which can lead to cracking. Additive likes silica fume is too expensive to use in the HSC in order to overcome the problems, however, the initiative of utilizing the rice husk ash (RHA) which have high silica content are apply for the design of HSC. The RHA is obtained by burning the rice husk which is an agro-waste material, and was found to have good pozzolanic material properties. This paper highlighted the study conducted in determining the effect of silica content in RHA in HSC production. The strength performance considered in this study is 60 N/mm2 and 70 N/mm2. The percentages used as cement replacement varies, i.e. 10%, 20%, 30%, 40% and 50% of RHA by cement weight, and with addition of superplasticizer. Compressive strength test was conducted at age of 28, 60 and 90 days to see the development of strength, while for the durability index performance, the Rapid Chloride Penetration Test (RCPT) tested at age 28, 60 and 90 days and water absorption test tested at age 28 and 90 days of water curing were performed. This research paper reported that 10% replacement of cement with RHA was found to be the optimum replacement in achieving the targeted strength, however, for durability index performance, higher replacement level (up to 50%) can be achieved, resulted in decreased in charge passed and decreased in water absorption, therefore, improved the durability performance of the concrete. These shows that high amount of silica in RHA gave some effects on the strength and durability of the HSC.