Evolution of recycled construction aggregates (RCA) pH and its compatibility with geosynthetics

Recycled Construction Aggregate (RCA) is now commonly used as a fill material in reinforced soil structures, often in combination with geosynthetic reinforcement. However, the alkalinity of recycled materials in contact with geosynthetics made from Polyethylene Terephthalate (PET) can lead to varying degrees of reduction in the mechanical resistance of the geosynthetic. When RCA is first produced, the concrete elements within it typically have a high initial alkalinity (pH > 9). However, the actual pH of mixed RCA varies depending on site conditions and time. A literature review has shown that while RCA initially has a high pH, the recycling process and its transformation into granulates lead to a gradual decrease in pH due to several influencing factors. Over time, the pH can drop to values below 9. Through a literature review and simplified laboratory tests, this paper examines the evolution of RCA’s pH and the key parameters influencing its changes. This study serves as an initial contribution to a better understanding of the conditions that determine the compatibility of RCA with PET geosynthetic reinforcement.