Transforming waste into strength: Analyzing concrete performance with recycled brick aggregates through fuzzy logic and Weibull distribution under varied curing conditions

Abstract The construction industry faces increasing environmental and sustainability challenges, including the depletion of natural resources and management of construction and demolition waste. Recycling brick waste as aggregate in concrete offers a promising solution to these challenges while potentially reducing the environmental footprint of concrete production. This study investigates the performance of concrete incorporating recycled brick aggregates (RBA) enhanced with polypropylene and carbon fibers under both humid and dry curing conditions. RBA was substituted at proportions ranging from 0% to 100%, while fiber reinforcement was added at 0.3% and 0.5% dosages. The experimental program evaluated mechanical properties through static loading tests (compressive, tensile, and flexural strength) and impact resistance at 7 and 28 days. A fuzzy logic model was developed to predict compressive strength, and impact strength data were analyzed using Weibull distribution. The substitution of 25% natural aggregates with RBA in concrete mixtures, when cured under humid conditions, resulted in a decrease in compressive, tensile, and flexural strengths by 4.84%, 6.91%, and 5.85%, respectively. With a 100% replacement of RBA, the reduction rates reached 43.12%, 39.65%, and 40.03%, respectively. The introduction of fibers into RBA-containing concrete mixtures effectively mitigated the negative impacts of RBA, with carbon fibers demonstrating superior performance compared to polypropylene fibers. Specifically, the reinforcement of mixtures containing 25% RBA with 0.5% carbon fibers yielded improvements in compressive, tensile, and flexural strengths of 3.53%, 5.33%, and 4.28%, respectively. Moreover, the incorporation of carbon fibers significantly enhanced both the first-crack strength and failure strength of the 25% RBA mixture, registering increases of 11.43% and 14.29%, respectively. In contrast, the identical RBA mixture without fiber reinforcement exhibited reductions in first-crack and failure strengths by 8.58% and 7.15%, respectively. The fuzzy logic model demonstrated high accuracy in predicting compressive strength (R² = 0.9763), while the Weibull distribution effectively characterized impact behavior (R² > 0.88). These findings provide valuable insights for incorporating RBA in concrete applications, particularly when enhanced with fiber reinforcement, contributing to more sustainable construction practices.