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<p>The limited availability of traditional supplementary cementitious materials (SCMs) has driven research on new easily accessible materials with pozzolanic properties. Thermally activated low-grade clays have shown good potential in that regard. At the edge of these clays are brick soils, with only a moderate content of clay minerals. This study investigates the potential of such thermally activated brick soils (TABS) as viable SCMs. Specifically, three brick soils deposited in the Czech Republic were calcinated at 650 °C and used as an SCM in the dosage of 5 to 25% of the total mix mass. Given that the calcinated soils contained only about 50% amorphous content, the mixture design was adapted to such composition, and the rational design was implemented. This means that the total amount of TABS was divided into two portions, one replacing the cement, while the second one replacing the finest aggregate. The portions were in the ratio of the determined amorphous and crystalline phases. This way, the reactive (i.e. amorphous) part partially replaced cement, while the non-reactive (i.e. crystalline) part of TABS was employed as the filler element. The designed high-strength concretes were investigated in terms of reaction heats, structure and phase composition, and basic physical and mechanical properties. In general, the pozzolanic reaction of the TABS resulted in the rise of alumina-bearing AFm and Aft phases at the expense of portlandite and tobermorite. The structure was more compact with a finer-grained crystal structure. The performance of the two composites depended on the replacement level (optimum was about 10–15%), while the third composites showed similar superior performance regardless of the TABS content. However, the highest replacement levels with cement dosage lowered by 37%, 40 and 50% also showed applicable properties. These findings demonstrate that brick soils, when properly activated and incorporated through rational design, are a promising SCM for sustainable high-performance concretes.</p>

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Thermally activated brick soils used as SCM in high-strength concrete

  • 期刊论文

  • 发表日期：

    2025年7月24日

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  • Vojtěch Pommer,
  • Dana Koňáková,
  • Kateřina Šádková,
  • Jaroslava Zatloukalová,
  • Petr Konvalinka,
  • Martin Keppert,
  • Eva Vejmelková

摘要

The limited availability of traditional supplementary cementitious materials (SCMs) has driven research on new easily accessible materials with pozzolanic properties. Thermally activated low-grade clays have shown good potential in that regard. At the edge of these clays are brick soils, with only a moderate content of clay minerals. This study investigates the potential of such thermally activated brick soils (TABS) as viable SCMs. Specifically, three brick soils deposited in the Czech Republic were calcinated at 650 °C and used as an SCM in the dosage of 5 to 25% of the total mix mass. Given that the calcinated soils contained only about 50% amorphous content, the mixture design was adapted to such composition, and the rational design was implemented. This means that the total amount of TABS was divided into two portions, one replacing the cement, while the second one replacing the finest aggregate. The portions were in the ratio of the determined amorphous and crystalline phases. This way, the reactive (i.e. amorphous) part partially replaced cement, while the non-reactive (i.e. crystalline) part of TABS was employed as the filler element. The designed high-strength concretes were investigated in terms of reaction heats, structure and phase composition, and basic physical and mechanical properties. In general, the pozzolanic reaction of the TABS resulted in the rise of alumina-bearing AFm and Aft phases at the expense of portlandite and tobermorite. The structure was more compact with a finer-grained crystal structure. The performance of the two composites depended on the replacement level (optimum was about 10–15%), while the third composites showed similar superior performance regardless of the TABS content. However, the highest replacement levels with cement dosage lowered by 37%, 40 and 50% also showed applicable properties. These findings demonstrate that brick soils, when properly activated and incorporated through rational design, are a promising SCM for sustainable high-performance concretes.