Effect of the addition of silica obtained from rice husk on physicochemical and mechanical properties of fibercement.

After replacing asbestos with other types of fibers used as reinforcement of cementitious matrices, it has been found that rice husk, an agro-industrial waste with high silica content, can be used to improve the properties of fibercement. In this work, the effect of adding different forms of silica (rice husk, rice husk ash, and silica microparticles) on fibercement's physicochemical and mechanical properties was investigated. Rice husk ash and silica microparticles were extracted from the rice husk incineration and acid leaching process. The chemical composition of silica was determined by X-Ray Fluorescence, and the ash leached with hydrochloric acid was found to contain more than 98% silica. Cement, fiberglass, additives, and different forms of silica were used to manufacture fibercement specimens in their different forms. Concentrations of 0%, 3%, 5%, and 7% were taken for each form of silica, and four replicates were performed. The setting time was 28 days, during which absorption, density, and humidity tests were performed. Experiments were statistically analyzed at a 95% confidence value, and it was determined that there are significant differences in the compressive resistance, density, and absorption in relation to the type of additive and the interaction between the type of additive and its percentage of addition, but not whit percentage of addition. It was found that the fibercement specimens with 3% of rice husk present a modulus of elasticity of 9.4% higher than de control sample. The use of rice husk as an additive in fibercement composites seems to be interesting because these agro-industrial wastes are inexpensive and easily available everywhere to utilize in the cement industry and also helpful in reducing environmental pollution due to their cost and the positive effect on their properties.