PSI - Issue 70

C. Raghu Rami Reddy et al. / Procedia Structural Integrity 70 (2025) 223–230

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relatively low mechanical strength and brittle failure behavior by Narayanan & Ramamurthy (2000). The high porosity, resulting from the intentional incorporation of stable air voids during mixing (as per ASTM C796-97), contributes to its lightweight character but compromises compressive, flexural, and tensile performance by Shanmugapriya & Kavitha (2017). Adding reactive mineral admixtures, like fly ash (FA) and metakaolin (MK), can greatly improve the performance of foamed concrete. and silica fume (SF), as recent advancements in mix design have shown. According to Zhang et al. (2023) and Karthik & Sudarsana Rao (2017), these materials enhance matrix densification, refine the pore structure, and take part in pozzolanic processes. Fly ash contributes to improved workability and long-term strength development by Kearsley & Wainwright (2002), metakaolin enhances early strength and reduces pore connectivity by Li et al. (2024), while silica fume, owing to its ultrafine particle size and high pozzolanic activity, acts as both a filler and a strength-enhancing additive by producing an ultra-dense C – S – H gel matrix by Shanmugapriya & Kavitha, (2017) & Chen et al. (2025). To counter the brittleness of foamed concrete, fiber reinforcement, especially with polypropylene (PP) fibers, has emerged as a successful strategy, per Zollo (1997). According to Liang et al. (2016) and Wang et al. (2024), PP fibers, when incorporated at a volume of 0.5% to 1.0% do not appreciably jeopardize the material's lightweight properties, while they tremendously boost the tensile capacity, impact resistance, and post-cracking ductility of foamed concrete. Moreover, Ma (2014) and Liu et al. (2023) add that the increase in wholeness and resilience of foamed concrete achieved with PP fibers makes it far more suitable and feasible for construction of structural and semi-structural entities. Despite recent advancementsThe long-term mechanical behaviour and microstructural evolution of foamed concrete including polypropylene (PP) fibers and mineral admixtures remain underexplored. Further research is needed to elucidate the specific interactions between these admixtures and PP fibers, particularly their influence on interfacial bonding, Refined pore structure and C-S-H gel morphology by Liu et al .(2023). Research in this area aims to completely assess the mechanical and microstructural characteristics of foamed concrete that has been reinforced with 0.8% polypropylene (PP) fibers and 10% the desired density is 1200 kg/m³, and the mineral admixtures used include silica fume, fly ash, or metakaolin.The study evaluated split tensile, compressive, and flexural strengths at 7, 14, 28, 56, and 90-day curing times. Amran et al. (2015) and Kearsley & Wainwright (2002) used scanning electron microscopy (SEM) to analyze microstructural changes, such as fiber-matrix bonding, hydration product shape, and pore structure. The primary objectives are to: (i) quantify the mechanical enhancements from incorporating fibers and admixtures; (ii) characterize the microstructural transformations induced by each fiber admixture combination; and (iii) identify the most effective admix ture for optimizing foamed concrete’s structural performance. The findings provide valuable guidance for developing durable, lightweight concrete with improved strength, expanding its applications in structural engineering Zhao et al. (2025). A 53-grade ordinary Portland cement that meets the requirements of IS: 12269-1987 (Bureau of Indian Standards, 1959), as well Class F fly ash, metakaolin, and silica fume. as mineral admixtures, were the raw materials employed in this investigation. A polycarboxylate ether (PCE)-based superplasticizer was incorporated to enhance workability. Following Ramachandran (1981), polypropylene (PP) fibers were introduced at a dosage of 0.8% by volume. The properties. The raw materials are summarized in Table 3. to ensure experimental consistency and reliability (Chen et al., 2025). The impact of polypropylene fibers mineral additives' influence on mechanical and microstructural qualities of foamed concrete was assessed by creating concrete specimens. The reference mix, M1, which included cement, water, foam, and superplasticizer, M2 (10% metakaolin + 0.8% PP fibers), M3 (10% fly ash + 0.8% PP filaments), and M4 (10% silica fume + 0.8% PP fibers) were the four mixes that were created. In all mixes, natural sand was utilized as the fine aggregate together with a protein-based foaming agent in order to reach the necessary density. Exactly the amounts of each ingredient are shown in Table 3. Following normal techniques, the specimens' mechanical properties At7,14,28,56, and 90 days, the flexural, splitting, and compressive tensile strengths were measured. following casting and curing under close observation. We used scanning electron microscopy to look at the broken specimens. (SEM) at 28 and 90 days to examine the internal matrix structure. The SEM focused on pore morphology, 2. Materials and Mix Proportions 2.1 Materials