PSI - Issue 70

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

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mixture, the following tests were conducted based on weight loss due to acid attack and weight gain due to salt encrustation. 4.1 SEM/XRD results SEM is a final step in determining the microlevel and relatively invisible bonding status between conventional concrete materials and substituted foreign matter at permissible amounts. Bonding qualities can be observed by observing the lines of least resistance, promoting fracture development and the possible structural arrangement of elements. The development of CSH gels and their even distribution for intra- and inter-structural stability are crucial evaluation indicators. The output details from Figure 1 demonstrate the applicability and potential for the replacement materials to play a significant part in a long-term mass production scenario, supporting the acceptance of CRACS as an improvised concrete alternative. The successively distorted peaks and dips in the X-ray diffractions, which represent the integrated mineralogy that contributes to the final CSH gel production and proliferation around the concrete constituents for inter-spatial bonding, further support the SEM results. The improvement of a concrete mantle with techno-economically supported replacement proportions for its fundamental materials with eco-friendly substitute equivalents can only be seen at the macro level. However, the implications at a nearly invisible microdomain should also be understood to anchor the dependability of the improvised concrete mix for its advantage over equality on par with the strength and other evaluation criteria at specified levels. The SEM/XRD tests used for this purpose demonstrated that the bonding between the mixed concrete materials, namely, cement, sand, aggregates, proportionate waste tire fragments, and steel slag, is excellent. The micro-level cleavages along the paths of least resistance to fractures or cracks were virtually filled with an even distribution of CSH gel diffusion among the constituents. 4.2.1 Reduction in HCl and H 2 SO 4 Immersion In the case of the HCl dip, the control concrete mixture lost 0.50 kg of weight, leaving an initial stabilized weight of 8.45kg for the cube examined, Fig.2(a). The percentage decrease in weight was calculated to be 4.73%, which is well under the permitted 10% limit for the control mix. For the optimized percentage combination of 9% RFA and 9% SS, the weight reduction was 0.267 kg for an initial stabilized weight of 8.372 kg, which was 3.18%. This demonstrates that the improved concrete has an advantage over HCl attack, with a lower proportion of sensitivity to corrosion than the control concrete mix. In the sulfuric acid dip test, the control mixture lost 0.31 kg of weight, which is equivalent to 3.66%. In the case of the finalized improvisation mix with 9% RFA and 9% SS, Fig. 2(b), the settled concrete mix experienced a weight decrease of 0.18 kg for an initial stabilized weight of 8.495 kg, totalling 2.11%. As a result, a countercheck with another acid assault by H 2 SO 4 demonstrated that the improved concrete mixture is more durable and resistant than the control concrete mixture. By and large, an acid attack is supposed to cause deterioration of the bonding between the concrete ingredients, whereas salt encrustation is supposed to add upon the weight via deposition, both of which are harmful to a set of concrete. Dipping the control concrete mixture in hydrochloric acid resulted in a 0.5 kg weight loss, with an initial stabilized weight of 8.45 kg for the cube examined. The weight loss was 4.73%, which was greater than the permitted limit of 10% for the control mixture. However, the improvised concrete mix outperforms the normal concrete mix by 3.18%, which is only slightly lower. In the case of the H 2 SO 4 mixture, the weight loss was 3.66% for the control mixture and 2.11% for the improved mixture of CRACS. As a result, in terms of weight decrease owing to acid invasion and CRACS, the improvised concrete mix outperformed the regular concrete mix by registering a comparatively low percentage of weight loss. 4.2.2 Weight increase due to exposure to salts (MgSO 4 and NaCl immersion) In contrast to acid when acid showers or the contact of acidic solutions with the concrete surface, salt incrustation is conceivable. This impact is illustrated by the weight gain caused by the deposition of salt layers by MgSO 4 and 4.2 Variations in weight