The effect of rice husk ash and silica as admixtures on the properties of concrete

Mageswaran, Thanujha (2024) The effect of rice husk ash and silica as admixtures on the properties of concrete. Project Report. Universiti Teknikal Malaysia Melaka, Melaka, Malaysia. (Submitted)

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Abstract

This study explores the impact of rice husk ash (RHA) and silica as admixtures on concrete properties for building applications. The research project used a 1:2:0.5 ratio for concrete production, with varying percentages of admixtures. Three types of mixtures were tested: RHA 1, RHA 2, and SP 1, with different amounts of cement, fine sand, water, and admixtures. The research follows ASTM standards and uses a detailed process flowchart to test various admixture ratios and percentages. The process flowchart outlines a detailed procedure for investigating the impact of waste materials as admixtures on concrete properties for buildings. The experiment begins with material selection, mixing ratio, and apparatus purchase. The slump test, compressive strength, water absorption, and scanning electron microscopy tests are conducted, analyzing concrete qualities and providing recommendations. Workability tests reveal that RHA enhances workability even with reduced cement content. Compressive strength tests show that an increase in RHA percentage may reduce compressive stress, while higher silica percentages boost compressive stress. Unconfined compressive strength of the mixture increases slower with higher RHA content and higher with longer curing age. Water absorption tests reveal that higher RHA percentages increase water absorption, potentially posing durability concerns. However, silica consistently shows improved moisture resistance, highlighting its effectiveness in mitigating water absorption issues. SEM analysis reveals that elevated RHA percentages create voids, fractures, and pores, indicating potential challenges at the microstructural level. As water evaporates, more voids form, increasing porosity, and filling these voids with air reduces thermal conductivity due to low thermal conductivity. The study's recommendations emphasize the need for careful admixture selection, considering the impact on both macroscopic and microscopic concrete properties. The findings contribute to the development of sustainable and enduring concrete mixes tailored to specific applications.

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