Theses and Dissertation

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Browsing Theses and Dissertation by Author "Hamisi, Hashimu"

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    Synthesis of High-Strength and Durable Metakaolin-Based Geopolymer Cured at Ambient Temperature
    (NM-AIST, 2025-08) Hamisi, Hashimu
    This study aimed to synthesize high-strength and durable metakaolin-based geopolymers cured at ambient temperature, with a focus on enhancing the pozzolanic reactivity of metakaolin. It employed Taguchi design methods to optimize the compressive strength. The growing need for environmentally friendly building materials has sparked interest in geopolymers, which offer a viable substitute for conventional cement-based systems. Metakaolin, a pozzolanic material that results from kaolin clay, significantly enhances the mechanical properties and durability of geopolymers, making it an ideal candidate for this application. Using The Response Surface Methodology under the Box-Behnken Design, the study systematically examined the effects of several key parameters, including calcination temperature (650-850°C), heating rate (1-19°C/min), and soaking time (1-12 h), revealing that a temperature of 765°C at a rate 10°C/min and soaking time of 6.46 h yields the most reactive Metakaolin, characterized by high pozzolanic reactivity and optimized particle morphology both critical factors for effective polymerization. In achieving maximum compressive strength, the Taguchi method was applied, facilitating a structured approach to assess the influence of multiple variables: The concentration of sodium hydroxide solution (NaOH: 8-12M), the ratio of the Na2SiO3 to NaOH (SS/SH-1.5-2.5), and the solution to binder ratio (S/B-0, 6-1.0) on the mechanical-properties of the resultant geopolymers. The findings indicate that the optimal formulation achieved compressive strengths exceeding 70 MPa at 12M NaOH, 2.5 SS/SH, and a solution-to-binder ratio of 0.80. This significant improvement is attributed to the synergistic effects of the highly reactive Metakaolin and the strategic optimization of mixing ingredients. The strategic incorporation of RHA enhances compressive strength and improves durability, as evidenced by the geopolymers’ strong resistance to rapid chloride permeability and acidic environments. Experimental results demonstrated minimal degradation in aggressive environments, underscoring the materials’ suitability for diverse construction applications. A dense, homogenous matrix necessary for the geopolymers' mechanical integrity was proven by microstructural investigation using methods including X-ray Diffraction (XRD) and Scanning Electron Microscopy (SEM). The development of extra binding phases through pozzolanic interactions between Rice Husk Ash and Metakaolin enhanced the composite material's overall performance.