Enhancing the Flexural Strength of Concrete Pavements with Recycled Aggregate Using Natural Rubber Latex Additive

The use of recycled concrete aggregate (RCA) in infrastructure activities has surfaced as a feasible strategy to reduce the reliance on natural aggregates and address environmental concerns related to construction waste disposal. This study aligns with the recent trends in sustainability by evaluating the enhancement of RCA properties through the incorporation of natural rubber latex (NRL), specifically for concrete pavement applications. Compressive strength (fc) and flexural (ff) strength assessments, microstructural examinations via energy-dispersive X-ray spectroscopy (EDX) and X-ray diffraction (XRD) analyses of RCA-NRL concretes were conducted. The dominant factors investigated were the ratios of dry rubber to cement (r/c) and water to cement (w/c). The presence of NRL retards cementitious products, resulting in reduced fc at all r/c levels but enhanced ff and ductility when r/c ratios were less than or equal to the optimum ratio. The RCA-NRL concretes, with w/c=0.3 at r/c≤1.0 and w/c=0.4 at r/c=0.5, consistently met the prescribed compressive strength (fc≥34.3 MPa) and flexural strength (ff≥4.2 MPa) requirements outlined by the local authority. However, when w/c>0.5, the addition of NRL led to a decrease in both fc and ff. The microstructural analysis confirmed the existence of NRL films in all concrete specimens containing RCA and NRL, which effectively contribute to the development of ff, particularly when the r/c ratio was lower than the optimal level. EDX and XRD analyses revealed the lower portlandite phase with a higher r/c value, indicating hydration retardation. Profound insights derived from this study underscore the intricate relationship between NRL and RCA, offering valuable guidance for optimizing NRL-modified concrete blends to achieve enhanced performance and environmental sustainability in construction projects.