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<p>One of the most commonly used materials in construction is concrete, with global production exceeding two billion tons annually. The production of ordinary Portland cement (OPC) consumes huge amounts of energy and releases significant quantities of CO<sub>2</sub>, negatively impacting the environment. A promising solution to this issue was using natural pozzolans as a partial replacement for cement, which can help reduce the environmental effects associated with the massive amounts of cement produced annually. This study explores using kaolin, bentonite, and glauconite as supplementary cementitious materials (SCM) as sustainable alternatives to cement to address environmental concerns. This study specifically investigates the influence of elevated temperatures on the mechanical and physical properties of cementitious concrete containing 20% cement replacement with these supplementary materials. The raw materials were tested both in their untreated state and after undergoing thermal treatment at 600 °C. Five groups were cast (G1: C the control mix), (G2: K, B, and G) without treatment, (G3: K600, B600, and G600) made with 600 °C- treated forms, G4 (KGB, untreated blend) and G5 (KGB600, thermally treated blend) after 28&#xa0;days of water curing in room temperature, three cubes per mix were exposed to (250, 300, 350 and 400 °C) for 2&#xa0;h, exposed to sudden water cooling, and then tested for compressive strength. The physical and chemical compositions of the raw materials were analyzed using X-ray diffraction (XRD) and X-ray fluorescence (XRF) techniques. The microstructure of the raw materials and samples was carried out using a scanning electron microscope (SEM–EDX). Results demonstrated that thermally treated SCMs significantly enhances the fire resistance. Compressive strength improvements over the control mix reached up to 39.6% at 250 °C. However, all mixes experienced strength degradation at higher temperatures (350–400 °C) due to thermal shock from water cooling, which induced microcracking and spalling. The study concludes that thermally activated natural pozzolans are effective SCMs for improving fire resistance, though the cooling method is a critical factor in post-fire performance.</p>

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Effect of high temperatures and suden cooling on the strength of cementitious concrete with kaolin, bentonite, and glauconite as supplementary cementitious materials

  • 期刊论文

  • 发表日期：

    2025年9月30日

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  • A. Mindil,
  • Amr B. ElDeeb,
  • Gamal M. A. Mahran,
  • Azza I. Anan

摘要

One of the most commonly used materials in construction is concrete, with global production exceeding two billion tons annually. The production of ordinary Portland cement (OPC) consumes huge amounts of energy and releases significant quantities of CO2, negatively impacting the environment. A promising solution to this issue was using natural pozzolans as a partial replacement for cement, which can help reduce the environmental effects associated with the massive amounts of cement produced annually. This study explores using kaolin, bentonite, and glauconite as supplementary cementitious materials (SCM) as sustainable alternatives to cement to address environmental concerns. This study specifically investigates the influence of elevated temperatures on the mechanical and physical properties of cementitious concrete containing 20% cement replacement with these supplementary materials. The raw materials were tested both in their untreated state and after undergoing thermal treatment at 600 °C. Five groups were cast (G1: C the control mix), (G2: K, B, and G) without treatment, (G3: K600, B600, and G600) made with 600 °C- treated forms, G4 (KGB, untreated blend) and G5 (KGB600, thermally treated blend) after 28 days of water curing in room temperature, three cubes per mix were exposed to (250, 300, 350 and 400 °C) for 2 h, exposed to sudden water cooling, and then tested for compressive strength. The physical and chemical compositions of the raw materials were analyzed using X-ray diffraction (XRD) and X-ray fluorescence (XRF) techniques. The microstructure of the raw materials and samples was carried out using a scanning electron microscope (SEM–EDX). Results demonstrated that thermally treated SCMs significantly enhances the fire resistance. Compressive strength improvements over the control mix reached up to 39.6% at 250 °C. However, all mixes experienced strength degradation at higher temperatures (350–400 °C) due to thermal shock from water cooling, which induced microcracking and spalling. The study concludes that thermally activated natural pozzolans are effective SCMs for improving fire resistance, though the cooling method is a critical factor in post-fire performance.