Enhancing the Mechanical and Durability Properties of Fully Recycled Aggregate Concrete Using Carbonated Recycled Fine Aggregates

Abstract

The global construction industry is increasingly utilizing concrete prepared from recycled aggregate as a substitute for natural aggregate. However, the subpar performance of recycled fine aggregate (RFA) has resulted in its underutilization, particularly in the structural concrete exposed to challenging environments, including those involving chlorine salts and freeze–thaw climates. This study aimed to enhance the performance of RFA as a substitute for river sand in concrete as well as fulfill the present demand for fine aggregates in the construction sector by utilizing accelerated carbonation treatment to create fully recycled aggregate concrete (FRAC) composed of 100% recycled coarse and fine aggregates. The impacts of incorporating carbonated recycled fine aggregate (C-RFA) at various replacement rates (0%, 25%, 50%, 75%, and 100%) on the mechanical and durability properties of FRAC were investigated. The results showed that the physical properties of C-RFA, including apparent density, water absorption, and crushing value, were enhanced compared to that of RFA. The compressive strength of C-RFC100 was 19.8% higher than that of C-RFC0, while the water absorption decreased by 14.6%. In a comparison of C-RFC0 and C-RFC100, the chloride permeability coefficients showed a 50% decrease, and the frost resistance increased by 27.6%. According to the findings, the mechanical and durability properties, the interfacial transition zones (ITZs), and micro-cracks of the C-RFC were considerably enhanced with an increased C-RFA content.

Impact of Interfacial Transition Zone on Concrete Mechanical Properties: A Comparative Analysis of Multiphase Inclusion Theory and Numerical Simulations

“…In previous studies on ordinary concrete, the density and strength of ITZ were much lower than those of aggregates and mortar, and were generally considered as weak links in concrete [5]. Some scholars enhance the mechanical properties of ITZ in recycled concrete by adding fiber materials or nano-scale materials into RC [6][7][8], and it is beneficial to study the specific changes of ITZs in a cross-scale way. The interface situation of RC is more complex, and it is difficult to observe and analyze the impact of different ITZs on the overall mechanical properties of RC.…”