The work described in this thesis has been performed in order to gain further understanding of the effect of physical properties and chemical composition of Rice Husk Ash as an admixture on the properties of mortar and concrete in related to the percentage of replacement ratio. However, the RHA properties based on the literature had a contradiction impact on the ordinary Portland cement (OPC) concrete performance. Thus, contradiction in performance of RHA properties gives a point of view offers challenge to more investigation. To reach these objects, different types of RHA (A, B, C, C1, C2, C3, C4, and C5) with various mortar and concrete were produced. The water-binder (w/b) ratios were maintained at 0.50, with variable replacement ratio range in between 0% to 80% of cement by weight. To obtain the rice husk ash properties, the silica structure, chemical composition, physical properties and microstructure form were quantitatively analyzed using a wide range of advanced techniques such as X-Ray Diffraction (XRD), X-Ray Fluorescence (XRF), Laser diffraction particle sizing and scanning electron microscopy (SEM). These investigations are crucial for gaining a more detailed understanding on how RHA properties act as a pozzolanic admixture in OPC concrete at high replacement ratio. The Influences of RHA on the, workability, compressive strength, splitting tensile strength, dry shrinkage, microstructure and durability of RHA mortar and concrete were evaluated. Finally, various heat treatments were applied to study the RHA silica structure. All the characteristics of these mortars and concrete containing RHA were compared to those of OPC mixtures. Overall, the results showed that RHA acts as a highly water absorbing material, which is also act as an internal curing agent in OPC. The decrease in the internal relative humidity and thus self-desiccation of OPC is reduced by the presence of RHA. The incorporation of RHA-A, B and C are improving the packing of the mortar and concrete mixtures, resulting in increased compressive and tensile strength. Moreover, with increase fineness of particles up to 4.0µm, RHA presented significant improvement in strength performance of mortar. In addition to that, with re-burned RHA-C at different temperature to time (C1, C2, C3, C4 and C5), a sustainable increase in the compressive and tensile strength were observed with C2 and C5, reactively. Drying shrinkage was another parameter was investigated and the results prove it that fineness of RHA particles effect directly on the drying shrinkage performance of concrete. Where, each of RHA-A and B (coarse particle size) strongly reduces drying shrinkage compare to RHA-C and C5. In addition to the strength and drying shrinkage, the chloride diffusion coefficient of concrete blended RHA was investigated. The results demonstrated the extent of the effect
The effect of rice husk ash on the mechanical and durability properties of concrete
Rasoul, B. I. (Author). 2018
Student thesis: Doctoral Thesis