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<p>Urbanization is increasing the demand for building and paving blocks. Hollow concrete and paver blocks are usually made with OPC, but alkali-activated materials can provide a sustainable alternative by repurposing the industrial waste. This work assesses the potential of alkali-activated copper slag (CS) based composites for producing paver and hollow concrete blocks. Sodium silicate and sodium hydroxide were used as activators with 6% alkali content and a range of modulus of silica (1, 1.25, and 1.5). In addition to powdered CS as precursor, raw CS (granular material) and recycled concrete aggregates were incorporated as fine and coarse fractions, respectively. Paver blocks with binder contents of 500–550&#xa0;kg/m<sup>3</sup> achieved compressive strengths of 37&#xa0;MPa–42&#xa0;MPa, meeting the M30–M35 requirements for non-traffic and light traffic use following IS 15658:2021. Hollow blocks with aggregate-to-binder ratios of 6:1 to 4:1 achieved strengths of 8–12&#xa0;MPa and densities of 1950–2050&#xa0;kg/m<sup>3</sup>, meeting Grade A (7&#xa0;MPa) requirements under IS 2185 (Part 1): 2005. Both block types satisfied code limits for density, water absorption, abrasion resistance, and drying shrinkage. Improved strength was linked to decreased open porosity and refined pore structure, as observed through decreased interfacial transition zone (ITZ) porosity with increased silicate modulus and binder content. Energy Dispersive Spectroscopy and Scanning Electron Microscopy highlighted compact microstructure, hydrated paste morphology, and probable Fe incorporation in the reaction phases. Effective use of alkali-activated CS, raw CS, and recycled aggregates in concrete blocks shows enhanced waste utilization and promotes the circular economy.</p> Graphical Abstract <p></p>

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Mechanical and Microstructural Characterization of Alkali-activated Copper Slag-based Sustainable Paver and Hollow Concrete Blocks

  • 期刊论文

  • 发表日期：

    2025年11月3日

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  • Dhiraj Surendra Mahajan,
  • Salman Muhammad

摘要

Urbanization is increasing the demand for building and paving blocks. Hollow concrete and paver blocks are usually made with OPC, but alkali-activated materials can provide a sustainable alternative by repurposing the industrial waste. This work assesses the potential of alkali-activated copper slag (CS) based composites for producing paver and hollow concrete blocks. Sodium silicate and sodium hydroxide were used as activators with 6% alkali content and a range of modulus of silica (1, 1.25, and 1.5). In addition to powdered CS as precursor, raw CS (granular material) and recycled concrete aggregates were incorporated as fine and coarse fractions, respectively. Paver blocks with binder contents of 500–550 kg/m3 achieved compressive strengths of 37 MPa–42 MPa, meeting the M30–M35 requirements for non-traffic and light traffic use following IS 15658:2021. Hollow blocks with aggregate-to-binder ratios of 6:1 to 4:1 achieved strengths of 8–12 MPa and densities of 1950–2050 kg/m3, meeting Grade A (7 MPa) requirements under IS 2185 (Part 1): 2005. Both block types satisfied code limits for density, water absorption, abrasion resistance, and drying shrinkage. Improved strength was linked to decreased open porosity and refined pore structure, as observed through decreased interfacial transition zone (ITZ) porosity with increased silicate modulus and binder content. Energy Dispersive Spectroscopy and Scanning Electron Microscopy highlighted compact microstructure, hydrated paste morphology, and probable Fe incorporation in the reaction phases. Effective use of alkali-activated CS, raw CS, and recycled aggregates in concrete blocks shows enhanced waste utilization and promotes the circular economy.

Graphical Abstract