Characteristics and optimization of cement concrete mixes with recycled asphalt pavement aggregates

In the road of sustainable development, using of recycled asphalt pavements (RAP) obtained from either demolition or rehabilitation of asphalt pavements with Portland cement concrete had become an essential practice. This can produce concrete mixtures with enhanced properties especially the higher ductility parallel with the expected environmental impacts. The current study is presented to assess the performance of cement concrete mixtures cast with different ratios of RAP as a partial replacement by volume of natural used coarse aggregate. RAP is the removed pavement material containing asphalt and aggregate. Concrete mixes were produced with replacement ratios of RAP at (0%, 15%, 30%, 45%, 60% and 100%) with various cement contents at (250, 300 and 350 kg/m(3)) and their performance were evaluated for appropriate concrete pavements' application. Moreover, fly ash with (10%, 20% and 30%) as a replacement with cement by weight and polypropylene fiber with volume fractions of (0.5% and 1%) were used. Compressive strength, splitting tensile strength, flexural strength, modulus of elasticity, Poisson's ratio and toughness were considered as the main properties of the investigated concrete mixtures. The test results showed that the evaluated mechanical strengths and elastic modulus values were decreased. However, a remarkable increasing in toughness and Poisson's ratio of RAP concrete specimens were recorded. Furthermore, the Analysis of Variance (ANOVA) and regression analysis by developing numerous relationships were proposed. The results of the regression model revealed that incorporating up to 100% RAP could be efficient to extend pavement's life due to the remarkable enhancing in toughness and the decreasing in modulus of elasticity of the concrete mixes in addition to its cost effectiveness. The multi-response optimization by response surface optimizer was used with composite desirability up to 1.

Automated summary

This study assessed the performance of cement concrete mixtures using recycled asphalt pavements (RAP) as a partial replacement. The results showed that RAP concrete exhibited enhanced toughness and decreased modulus of elasticity, contributing to the extension of pavement life.