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<p>Lightweight foamed concrete (LWFC) has attracted attention for its low density, thermal insulation, and flowability. However, its brittleness and reduced tensile resistance limited its structural applications. Previous studies focused on supplementary cementitious materials or fiber reinforcement separately, whereas the combined effect of binder modification with mono- or hybrid-fiber systems on the mechanical, durability-related, ultrasonic, thermal, and microstructural characteristics of structural-grade LWFC has been rarely reported. Seven LWFC mixtures were developed in the laboratory with a w/c ratio of 0.32 and a constant target density. For supplementary material, silica fume and ground granulated blast-furnace slag (GGBFS) were used, while steel, carbon, and polypropylene fibers were incorporated as a single or hybrid-fiber strengthening system. At 28 days of curing, hardened densities, workability, compressive strength, splitting tensile strength, flexural strength, modulus of elasticity, water absorption (WA), ultrasonic pulse velocity (UPV), thermal conductivity, and microstructure were evaluated. Results indicated that all silica fume-based mixtures outperformed slag-based mixtures, attributed to pozzolanic activity and subsequent matrix densification. The SF–StF–CF mixture achieved a compressive strength of 46&#xa0;MPa, representing a 46% increase compared to the SG–StF mixture (31.5&#xa0;MPa), and an increase in the tensile splitting strength of 48.7% (from 3.12 to 4.64). The hybrid fiber systems enhanced the compressive strength, reduced water absorption, and increased the ultrasonic pulse velocity of concrete, suggesting higher internal compactness and reduced porosity in the mixtures. The fibrous interlocking effects reduced workability, but thermal conductivity remained within the lightweight concrete insulation range. The SEM results and visual analysis suggested these improvements are linked to fiber-bridging mechanisms, suitable interfacial bonding, and pore refinement. The proposed LWFC system show potential for structural applications and energy-efficient building components.</p>

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Mechanical Performance of Structural Lightweight Foamed Concrete Reinforced with Hybrid Fibers and Supplementary Cementitious Materials

  • 期刊论文

  • 发表日期：

    2026年7月14日

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  • Wahage Ibrahim Abdul-Kareem,
  • Nagham Tariq Al-shafi’i,
  • Zainab Mohammed Ali Hussien

摘要

Lightweight foamed concrete (LWFC) has attracted attention for its low density, thermal insulation, and flowability. However, its brittleness and reduced tensile resistance limited its structural applications. Previous studies focused on supplementary cementitious materials or fiber reinforcement separately, whereas the combined effect of binder modification with mono- or hybrid-fiber systems on the mechanical, durability-related, ultrasonic, thermal, and microstructural characteristics of structural-grade LWFC has been rarely reported. Seven LWFC mixtures were developed in the laboratory with a w/c ratio of 0.32 and a constant target density. For supplementary material, silica fume and ground granulated blast-furnace slag (GGBFS) were used, while steel, carbon, and polypropylene fibers were incorporated as a single or hybrid-fiber strengthening system. At 28 days of curing, hardened densities, workability, compressive strength, splitting tensile strength, flexural strength, modulus of elasticity, water absorption (WA), ultrasonic pulse velocity (UPV), thermal conductivity, and microstructure were evaluated. Results indicated that all silica fume-based mixtures outperformed slag-based mixtures, attributed to pozzolanic activity and subsequent matrix densification. The SF–StF–CF mixture achieved a compressive strength of 46 MPa, representing a 46% increase compared to the SG–StF mixture (31.5 MPa), and an increase in the tensile splitting strength of 48.7% (from 3.12 to 4.64). The hybrid fiber systems enhanced the compressive strength, reduced water absorption, and increased the ultrasonic pulse velocity of concrete, suggesting higher internal compactness and reduced porosity in the mixtures. The fibrous interlocking effects reduced workability, but thermal conductivity remained within the lightweight concrete insulation range. The SEM results and visual analysis suggested these improvements are linked to fiber-bridging mechanisms, suitable interfacial bonding, and pore refinement. The proposed LWFC system show potential for structural applications and energy-efficient building components.