PSI - Issue 70

R. Mohanraj et al. / Procedia Structural Integrity 70 (2025) 409–416

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cement mortar. The results show that geopolymers have better interfacial adhesion, reduced porosity, flexural strength, and toughness with rubber aggregates, although they are weaker in compressive strength (Zheng et al. 2021). Geopolymers are more environmentally friendly but costlier. Further research will optimize mix designs with rubber aggregates (Piro et al. 2024). This study aims to investigate the durability of an improved concrete mixture incorporating RFA and SS by evaluating its resistance to acid attack and salt encrustation. The research included weight loss measurements following immersion in hydrochloric and sulfuric acids and weight gain measurements following exposure to magnesium sulfate and sodium chloride solutions. Additionally, scanning electron microscopy (SEM) and X-ray diffraction (XRD) analyses were conducted to examine the microstructural changes and bonding characteristics within the concrete matrix. By comparing the performance of the improvised mix to that of a conventional control mix, this study seeks to validate the potential of using RFA and SS as sustainable and durable alternatives in concrete production. 2. Materials and methodology The materials used in this study included ordinary Portland cement (OPC) conforming to IS: 8112-2012, natural river sand and rubber fine aggregate (RFA) derived from waste rubber tires, crushed granite aggregates, steel slag (SS), and potable water. Two concrete mixes were prepared, a control mixture (CC) and an optimized mixture with 9% RFA and 9% SS (CRACS), based on the IS 10262:2009 guidelines (Mohanraj and Vidhya 2024). The concrete cubes were cast, cured for 28 days, and subjected to durability tests, including acid attack and salt encrustation (Mohanraj et al. 2024). The samples were immersed in 5% solutions of hydrochloric acid (HCl) and sulfuric acid (H 2 SO 4 ) for acid attack tests and 5% solutions of magnesium sulfate (MgSO 4 ) and sodium chloride (NaCl) for salt encrustation tests, with weight changes recorded after 28 days (Ortega-López et al. 2018). The percentage weight loss and gain were calculated to assess durability. Additionally, scanning electron microscopy (SEM) and X-ray diffraction (XRD) analyses were conducted to examine the microstructural characteristics and bonding of the cement matrix with RFA and SS, focusing on the formation and distribution of calcium silicate hydrate (C-S-H) gels and identifying the mineralogical composition and crystalline phases (Raghav et al. 2021; Mohanraj & Krishnasamy 2024). The experimental data were analysed to compare the durability performance of the control and improved mixes, validating the potential of the improved concrete mixture for sustainable construction applications (Nguyen et al. 2021). 3. Experimental Study This experimental study aimed to evaluate the durability of an improved concrete mixture incorporating rubber fine aggregate (RFA) and steel slag (SS) as partial replacements for natural aggregates. The materials used in the study included Ordinary Portland Cement (OPC) conforming to IS: 8112-1989, natural river sand, RFA derived from waste rubber tires, crushed granite aggregates, SS, and potable water (Algaifi et al. 2024). Two concrete mixes were prepared following the IS 10262:2009 guidelines: a control mix (CC) and an improved mix (CRACS) containing 9% RFA and 9% SS (Che et al. 2024). The concrete cubes were cast and cured for 28 days (Qureshi et al. 2020). After curing, the samples were subjected to durability tests, including acid attack and salt encrustation. For the acid attack test, the samples were immersed in 5% solutions of hydrochloric acid (HCl) and sulfuric acid (H 2 SO 4 ) for 28 days. The weight loss of the concrete cubes was recorded, and the percentage weight loss was calculated to assess the resistance of the concrete to acid attack. For the salt encrustation test, the samples were immersed in 5% solutions of magnesium sulfate (MgSO4) and sodium chloride (NaCl) for 28 days (Loganathan et al. 2022). The weight gain of the concrete cubes was recorded, and the percentage weight gain was calculated to evaluate the susceptibility of the concrete to salt deposition (Velumani et al. 2023). In addition to these tests, scanning electron microscopy (SEM) and X-ray diffraction (XRD) analyses were conducted to investigate the microstructural characteristics of the concrete mixtures. SEM analysis provided detailed images of the bonding between the cement matrix and the RFA and SS, highlighting the formation and distribution of C-S-H gels. XRD analysis revealed the mineralogical composition and crystalline phases present in the concrete, further supporting the findings from the SEM analysis (Gopalakrishnan et al. 2024).