Experimental Investigation of Sand Concrete Reinforced with PET Fibers and Recycled Brick Sand

This study addresses the urgent environmental necessity of recycling waste due to the rapid depletion of natural aggregates in construction. It specifically focuses on valorizing locally abundant waste materials, recycled brick sand and PET bottles, to develop a sustainable sand concrete composite formulated using the SABLOCRETE method, a research area that remains relatively underexplored. The primary aim is to experimentally evaluate the performance of Sand Concrete (SC) modified with Recycled Brick Sand (RS) and Polyethylene Terephthalate Fibers (PETF). Assessing their impact of these materials on fresh properties, mechanical strength, porosity, shrinkage, and residual strength after exposure to high temperatures.

Using the SABLOCRETE method, sand concrete mixtures were designed by replacing natural sand with 0-100% RS and incorporating PETF at 0.3-1.2% by volume. Standard testing procedures evaluated workability, compressive and flexural strength at 7, 28, and 90 days, porosity, Ultrasonic Pulse Velocity (UPV), and 300-day shrinkage. Additionally, specimens were heated to 1000°C to assess thermal resistance.

Workability decreases with higher RS and PETF content. A 50% RS replacement combined with 1.2% PETF yielded optimal mechanical performance, improving compressive strength by up to 13% and flexural strength by up to 11% compared to the control mix, while reducing porosity and shrinkage by up to 45%. High-temperature exposure significantly degrades strength, particularly in 100% RS mixes, with strength losses reaching 63-66% at 1000°C, and PETF melting above 400°C.

While RS tends to increase shrinkage due to its higher water absorption, the incorporation of PETF effectively counteracts this by limiting crack formation. The synergistic combination of 50% RS and 1.2% PETF demonstrates that mechanical and durability improvements are achievable through optimized mix design. Nevertheless, thermal resistance remains a critical limitation, as high RS content and PETF melting at elevated temperatures substantially compromise fire performance, which must be considered in structural applications.

A mix of 50% recycled brick sand and 1.2% PET fibers offers a viable, eco-friendly alternative for the construction sector, balancing mechanical performance with waste reduction. However, fire resistance remains a key limitation that must be considered in practical applications, and workability must be managed through adjusted superplasticizer dosages.