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<p>Supplementary cementitious materials (SCMs) derived from natural rock powders represent a promising strategy for reducing cement consumption and associated CO₂ emissions in concrete production. This study investigates the systematic application of gneiss powder (GP), sourced from the Egyptian Eastern Desert, as a direct cement replacement in ordinary concrete. GP was incorporated at replacement levels of 3, 6, 9, 12, and 15% by cement weight, and its effects on the physical, mechanical, and microstructural properties of concrete were comprehensively evaluated. The Strength Activity Index (SAI) was conducted on GP-mortar mixtures to evaluate pozzolanic performance, while physical properties were assessed through standard consistency, setting time, and workability tests. Mechanical performance was evaluated by measuring compressive, splitting tensile, and flexural strengths at multiple curing ages. A comprehensive microstructural analysis using Scanning Electron Microscopy (SEM) and Energy-Dispersive X-ray Spectroscopy (EDX) was conducted to understand the hydration mechanisms. The SAI achieved 91%, exceeding the 75% minimum requirement of ASTM C618, confirming GP's classification as an effective pozzolanic material. Increasing GP content progressively elevated water demand and accelerated setting times, while significantly reducing workability. The 9% GP replacement level proved optimal, achieving compressive strength improvements of 48.1%, 38.8%, and 32.4% at 7, 28, and 90&#xa0;days, respectively, alongside increases of 22.4% and 18.3% in splitting tensile and flexural strengths at 28&#xa0;days. SEM and EDX analyses confirmed that the optimal mixture produced a denser, nonporous matrix with enhanced calcium silicate hydrate content and a low Ca/Si ratio, underscoring the superior pozzolanic activity of GP. These findings confirm that GP can effectively enhance concrete performance while contributing to carbon emissions reduction through partial cement replacement, establishing it as a viable and sustainable SCM for ordinary concrete production.</p>

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Utilizing Gneiss Powder as Supplementary Cementitious Material in Sustainable Concrete

  • 期刊论文

  • 发表日期：

    2026年6月17日

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  • A. Serag Faried,
  • Yasser S. Ibrahim,
  • Abdelhalim S. Mahmoud,
  • Mohamed M. Abdelaziz

摘要

Supplementary cementitious materials (SCMs) derived from natural rock powders represent a promising strategy for reducing cement consumption and associated CO₂ emissions in concrete production. This study investigates the systematic application of gneiss powder (GP), sourced from the Egyptian Eastern Desert, as a direct cement replacement in ordinary concrete. GP was incorporated at replacement levels of 3, 6, 9, 12, and 15% by cement weight, and its effects on the physical, mechanical, and microstructural properties of concrete were comprehensively evaluated. The Strength Activity Index (SAI) was conducted on GP-mortar mixtures to evaluate pozzolanic performance, while physical properties were assessed through standard consistency, setting time, and workability tests. Mechanical performance was evaluated by measuring compressive, splitting tensile, and flexural strengths at multiple curing ages. A comprehensive microstructural analysis using Scanning Electron Microscopy (SEM) and Energy-Dispersive X-ray Spectroscopy (EDX) was conducted to understand the hydration mechanisms. The SAI achieved 91%, exceeding the 75% minimum requirement of ASTM C618, confirming GP's classification as an effective pozzolanic material. Increasing GP content progressively elevated water demand and accelerated setting times, while significantly reducing workability. The 9% GP replacement level proved optimal, achieving compressive strength improvements of 48.1%, 38.8%, and 32.4% at 7, 28, and 90 days, respectively, alongside increases of 22.4% and 18.3% in splitting tensile and flexural strengths at 28 days. SEM and EDX analyses confirmed that the optimal mixture produced a denser, nonporous matrix with enhanced calcium silicate hydrate content and a low Ca/Si ratio, underscoring the superior pozzolanic activity of GP. These findings confirm that GP can effectively enhance concrete performance while contributing to carbon emissions reduction through partial cement replacement, establishing it as a viable and sustainable SCM for ordinary concrete production.