Development of an environmental-friendly durable self-compacting concrete.

Current construction practices rely heavily on natural sand and Portland cement, both of which have environmental drawbacks. Natural sand extraction contributes to ecological degradation, while cement production is energy-intensive and carbon-intensive. Prior research has shown that manufactured sand (M-sand) and fly ash (FA) can serve as partial replacements in concrete mixtures. However, the long-term durability of such mixtures in aggressive environments remains unclear. This gap motivated researchers to test SCC formulations with M-sand and FA. The study aims to evaluate the environmental and mechanical performance of these alternatives. No prior work had resolved the optimal replacement levels for both materials. The need for sustainable building materials has driven this investigation. The focus is on sulphate resistance, a key factor in concrete durability. This paper addresses the need for eco-friendly construction materials.

The study aimed to develop an environmentally friendly self-compacting concrete (SCC) by substituting natural sand and cement with manufactured sand (M-sand) and fly ash (FA). The researchers sought to determine the optimal replacement levels for these materials. They also aimed to compare the fresh and hardened properties of the new SCC mix with a conventional mix. The goal was to assess the durability of the new SCC in a sulphate environment. The study focused on compressive strength, weight change, and sorptivity over 360 days. The researchers wanted to evaluate micro-structural changes using XRD, SEM, and EDS. The motivation was to create a sustainable concrete alternative with proven durability. This work addresses the need for eco-friendly construction materials.

The study involved partial replacement of natural sand with manufactured sand (M-sand) and ordinary Portland cement with fly ash (FA). Two SCC mixes were prepared: SCC-I (100% OPC + 100% N-sand) and SCC-II (80% OPC + 20% FA + 50% N-sand + 50% M-sand). Fresh concrete properties were tested using slump flow, T₅₀ time, V-funnel, L-box, U-box, and J-ring tests. After 28 days of curing, the samples were immersed in a 2.0 g/l ammonium sulphate solution for 360 days. Compressive strength, weight change, and sorptivity were measured periodically. Micro-structural analysis was conducted using X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy-dispersive spectroscopy (EDS). The data were used to compare the performance of the two mixes.

The optimal replacement level of OPC with FA was found to be 20%, and for N-sand with M-sand, it was 50%. SCC-II showed improved workability in fresh state tests like slump flow and V-funnel. After 360 days of sulphate exposure, SCC-II retained higher compressive strength compared to SCC-I. The weight loss in SCC-II was lower than in SCC-I, indicating better durability. Sorptivity values for SCC-II were consistently lower, suggesting reduced permeability. XRD analysis revealed the formation of additional hydration products in SCC-II. SEM and EDS confirmed the denser microstructure and reduced porosity in SCC-II. These findings suggest that FA and M-sand enhance the durability of SCC in sulphate environments.

The study demonstrated that replacing 20% OPC with FA and 50% N-sand with M-sand improves the durability of self-compacting concrete (SCC). SCC-II showed better performance in sulphate exposure tests compared to SCC-I. The researchers propose that FA and M-sand contribute to a denser microstructure and lower permeability. The findings suggest that these materials can make SCC more environmentally friendly. The compressive strength of SCC-II remained stable over 360 days of sulphate exposure. XRD, SEM, and EDS analyses confirmed the formation of hydration products and reduced porosity. The authors suggest that this mix design could be used in aggressive environments. The results support the use of FA and M-sand in sustainable concrete formulations.