Multi-performance optimization of sustainable concrete incorporating sugarcane bagasse ash and recycled PET fibers using a two-stage AHP–TOPSIS framework

The construction industry is increasingly seeking sustainable alternatives to reduce cement consumption and valorize industrial and plastic wastes without compromising structural performance. This study investigates the combined utilization of sugarcane bagasse ash (SCBA) as a supplementary cementitious material and recycled polyethylene terephthalate (PET) fibers for developing sustainable concrete suitable for structural and pavement applications. Concrete mixtures incorporating 5%, 10%, and 15% SCBA as cement replacement and 0.5%,1%,1.5% and 2.0% recycled PET fibers were evaluated through a two-stage experimental and decision-making framework. Initially, all sixteen concrete mixtures were assessed for workability and 28-day compressive strength, followed by a preliminary AHP–TOPSIS analysis to identify the optimum SCBA replacement level. Subsequently, the selected 10% SCBA series was further investigated through split tensile strength, flexural strength, water absorption, abrasion resistance, X-ray diffraction (XRD) analysis, and field-scale validation. The preliminary AHP–TOPSIS analysis identified the 10% SCBA series as the optimum replacement level, while the final AHP–TOPSIS analysis ranked the mixture containing 10% SCBA and 1.0% recycled PET fiber (P₂S₂) as the optimum overall concrete. The highest compressive strength (35.35 MPa) and split tensile strength (3.79 MPa) were achieved by P₃S₂ (10% SCBA + 1.5% PET fiber), whereas P₂S₂ exhibited the highest flexural strength (6.77 MPa), the lowest water absorption (3.02%), and superior abrasion resistance (2.88 mm). XRD analysis confirmed the formation of hydration products responsible for matrix densification in the optimum concrete. The incorporation of 10% SCBA reduced cement consumption by 43.33 kg/m³ , corresponding to an estimated CO₂ emission reduction of 34.66–41.16 kg CO₂/m³ . Furthermore, the optimum mixture was successfully implemented in a field-scale pedestrian rigid pavement, demonstrating its practical applicability. The proposed multi-stage evaluation framework establishes that the combined utilization of SCBA and recycled PET fibers can produce sustainable concrete with enhanced mechanical performance, improved durability, and reduced environmental impact, supporting the development of resource-efficient construction materials.