Properties of Structural Concrete Made by Recycled Sand, Flyash, and Silica: A Study Towards Enhancing Sustainability in the Concrete Industry

Natural sand and high OPC utilization in the concrete industry have affected our environment and caused climate change. This study developed a novel methodology to prepare modified sand by adding (50% R-Sand + 50% M-Sand) to replace 100% natural sand. The two SCMs (5-20% of FA) and 10% of optimized SF) were added to the four newly developed concrete mixes. The developed sustainable design mix concrete achieved the design and target strength after a curing period of 28 days. The findings for flexural strength showed comparable trends. Significant strength improvement was also seen at later curing ages till 182 days. The water absorption and sulphuric acid attacks of design mix concrete at the hardened stage were also measured. The analysis reveals that water absorption percentages tend to decline as the curing age progresses. The developed mixes show better resistance against sulphuric acid attacks than the reference mix NAC*. A mass loss of around 5% was discovered, much closer to the published studies. The developed mix 15FASFRSC showed consistent results when the modified sand (50%R-Sand+50%M-Sand) was combined with the SCMs of (15%FA+10%SF). Hence, the mix 15FASFRSC is the best sustainable mix for the concrete industry.