Browsing by Author "Mukama Mathias"

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    Investigating the Use of Chert Powder as a Partial Replacement of Cement in Concrete
    (Uganda Christian University, 2025-04-19) Mukama Mathias
    This study investigated the use of chert powder as a partial replacement for cement in concrete, particularly to improve concrete resistance against sulphate attack. Chemical composition using X-Ray Fluorescence (XRF) showed a combined composition of 97.65% for SiO₂, Al₂O₃, and Fe₂O₃, exceeding the ASTM C618 required minimum of 70%, confirming chert powder's pozzolanic properties. With a specific gravity of 2.805 and fineness of 4.51%, chert powder had physical properties comparable to Ordinary Portland Cement (OPC). Tests on consistency, setting time, and strength activity index further justified its suitability as a supplementary cementitious material (SCM). Class 40 concrete mix designs incorporating 0% to 20% chert powder were prepared and tested. The 10% partial replacement rate showed optimal results, with increase in workability of about 7.50%, Compressive strength increase of about 4.14% (That is from 48.2MPa to 50.3Mpa). Water absorption was reduced by 22.73% indicating improved durability. Additionally, concrete exposed to a 50 g/L sodium sulphate solution showed reduced expansion of about 0.201% and minimal strength loss of about 7.48%, thus reflecting a 75.15% improvement in sulphate resistance of concrete at 10% replacement.