Fiber-Reinforced Foam Concrete Using Quarry Micro Fines and Sugarcane Bagasse Ash: A Box–Behnken Design Optimization and Performance Assessment

Foam concrete is well-appreciated for its thermal and acoustic benefits and is prepared by introducing foam into cement slurry/mortar. The current research examines the feasibility of Quarry Micro Fines (QMF), a waste generated from the quarries during sand manufacturing, as a substitute for fine aggregate in the preparation of foam concrete. During the preparation of concrete, a portion of cement is replaced with sugarcane bagasse ash (SCBA), while polypropylene (PP) fibers are added to improve the shrinkage resistance and tensile strength of the resulting concrete. A three-factor, three-level Box–Behnken Design (BBD) in Response Surface Methodology (RSM) was used to optimize the compressive strength of foam concrete, considering QMF (0%, 50%, 100%) by weight of fine aggregate, SCBA (0%, 10%, 20%) by weight of cement, and PP fiber (0.2%, 0.4%, 0.6%) by volume of foam concrete as variables. The three mixtures, including control (FC), mix with 50% QMF, 10% SCBA, and 0.4% PP fiber (F50S10F0.4), and mix with 100% QMF, 10% SCBA, and 0.4% PP fiber (F100S10F0.4), were chosen for a more in-depth investigation based on the test results. While Q50S10F0.4 achieved the highest compressive strength (6.18 MPa), Q100S10F0.4 showed the best overall performance, with low water absorption of 14.10%, porosity of 20.17%, UPV 2388 m/s, and RCPT values of 1407.96 Coulombs. The modified mixtures exhibited enhanced bonding and pore enhancement as demonstrated by scanning electron microscopy and mercury intrusion porosimetry analyses. The study highlights the effective use of QMF, SCBA, and PP fibers in producing high-performance, sustainable foam concrete.