Alkaline Durability and Environmental-Economic Sustainability Assessment of Cementitious Composites with Manufactured Sand and Hybrid Fiber-Reinforcement

Engineered Cementitious Composites (ECC) are a modern class of high-performance fiber-reinforced cementitious composites (HPFRCC) designed to exhibit strain-hardening behavior through multiple steady-state cracking. Apart from the better performance of the ECC matrix, production costs also play an essential part in large-scale applications, especially in developing countries. This study investigated the economic feasibility, durability performance, and environmental impact of ECC incorporating PVA-polyester fiber reinforcement and manufactured sand (M-sand) while maintaining the structural performance. Durability assessments were conducted for different alkaline conditions, representing the cementitious alkalinity. The immersion test results revealed that polyester fibers demonstrated considerable degradation, reaching a mass loss of 13.25% under high alkalinity at 60°C, whereas PVA fibers exhibited superior resistance. In addition, Fourier Transform Infrared Spectroscopy (FTIR) and microstructural investigations confirmed significant hydrolysis and surface etching in polyester fibers, whereas PVA fibers experienced negligible degradation despite some molecular changes. This study also evaluated alkali-silica reactivity (ASR) potential with different geographical M-sand samples and described that the prepared ECC mixtures effectively mitigated ASR, enabling the sustainable use of varying M-sand sources. Detailed production data of M-sand were collected from multiple locations, especially coastal areas where river sand use is restricted, and their emission and energy factors were evaluated systematically. Moreover, replacing a portion of PVA with polyester fibers and river sand with M-sand reduced the material cost by 20%, overall carbon emission by 8.21%, and energy consumption by 25%. The research presented a balanced approach for ECC mixture design, which is durable, cost-effective, and environmentally sustainable, while also outlining future recommendations on material refinement.