PSI - Issue 71

Yash Rathore et al. / Procedia Structural Integrity 71 (2025) 401–408

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1. Introduction The concrete industry is a significant consumer of natural resources and a notable contributor to global CO 2 emissions (Felipe Arbeláez Pérez et al., 2024). As the demand for concrete in infrastructure projects continues to grow, there is an urgent need to develop more sustainable and environmentally friendly concrete mixtures (Coffetti et al., 2022; Kioumarsi & Plevris, 2024). This necessity has driven extensive research into using supplementary cementitious materials (SCMs) and alternative aggregates in concrete production. Among the SCMs being explored, MK and RHA have attracted significant attention due to their pozzolanic properties and their potential to enhance concrete performance (Pillay et al., 2022; Siddika et al., 2021). MK, produced by calcining kaolinite clay at temperatures ranging from 650-800°C, is a highly reactive pozzolan known for significantly improving concrete properties (Shi et al., 2022). Studies show that MK can increase compressive strength, reduce permeability, and enhance resistance to chemical attacks when used as a partial cement replacement (Dhinakaran et al., 2012). The optimal replacement level for MK typically ranges from 10-15% of the cement's weight, although some research suggests benefits even at higher levels of 20-25% (Homayoonmehr et al., 2021; Mansour & Al Biajawi, 2022; Siddique & Klaus, 2009). RHA, a by-product of rice milling rich in amorphous silica, has also shown potential for improving concrete's durability and strength (Antiohos et al., 2014; Lacerda Gomes et al., 2023). When processed correctly, RHA can enhance workability, increase compressive strength, and improve resistance to chloride penetration (Jayanti et al., 2016; Vieira et al., 2020). The ideal replacement level for RHA usually falls between 10-20% of the cement's weight (Alex et al., 2016; Endale et al., 2022; Siddika et al., 2021). While the individual impacts of MK and RHA on concrete properties are well understood, there is limited research on their combined use. The synergistic use of both MK and RHA as partial cement replacements might lead to better concrete performance by combining MK's early strength benefits with the long-term durability improvements offered by RHA. The rapid depletion of natural river sand resources has highlighted the need to find alternative fine aggregates for concrete production (Anh et al., 2023; Rathore & Raheem, 2025b). M sand, produced by crushing rock, has emerged as a viable substitute for river sand (Rathore & Raheem, 2024, 2025a). Research indicates that concrete made with M-sand can match or even surpass the strength and durability of conventional concrete (Nadimalla et al., 2020; Shen et al., 2018). The angular shape and rough texture of M-sand particles enhance their bond with cement paste, potentially leading to improved concrete strength (Kavya & Venkateshwara Rao, 2020). In the Indian subcontinent, Deccan basalt is a widely available rock formation (Bose, 1972). Using Deccan basalt M sand in concrete not only addresses the shortage of river sand but also utilizes a locally abundant resource, which can reduce transportation costs and associated environmental impacts. Although the benefits of using MK, RHA, and M sand individually in concrete are well recognized, there has been little research on their combined effects. The interactions between these cement replacements (MK and RHA) and alternative fine aggregates (M-sand) in concrete mixtures remain largely unexplored, representing a significant gap in sustainable concrete technology knowledge. This study seeks to address this gap by examining the combined effects of using RHA and MK as partial cement replacements, alongside Deccan basalt M-sand as a substitute for river sand in concrete. The research will investigate various mix proportions to determine optimal replacement levels, focusing on their impact on mechanical strength development and concrete durability. Additionally, this study will explore how these alternative materials interact within a complex concrete system, potentially leading to innovative mix designs that optimize performance while reducing environmental impact. The findings could have important implications for sustainable concrete technology, especially in regions where Deccan basalt is abundant, and rice husks are readily available as an agricultural by-product. 2. Material Overview and Key Properties In this study, grade 43 OPC, conforming to IS 269:2015 standards is used (IS 269, 2015). MK and RHA are employed as SCMs, with specific gravities of 2.24 and 2.40, respectively. Fig.1(a) and Fig.1(b) show images of MK and RHA. The particle size distribution of OPC 43 grade, MK, and RHA is presented in Fig. 2(a). Among the three binder materials, MK was the finest, while RHA was coarser than both OPC and MK. The fine aggregates consist of locally sourced river sand and Deccan basalt M-sand from the Deccan region of Madhya Pradesh. Both types of sand comply with zone II specifications according to BIS: 383-2016 (BIS 383, 2016). The river sand has a fineness modulus of 3.03 and a specific gravity of 2.68, while the Deccan basalt M-sand has a fineness modulus of 2.76 and a specific gravity of 2.84. An image of the crushed Deccan basalt M-sand is shown in Fig.1(c). For coarse aggregates, crushed basalt stone is used, which

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