Performance of concrete containing sulfate-eroded recycled aggregates

Abstract

The original concrete subjected to environmental attack will change the properties of recycled aggregates, thereupon affecting the performance of recycled concrete. However, there is a lack of research that considers such impact. This study aims at providing knowledge on the performance of concrete containing sulfate-eroded recycled aggregates considering the effect of erosion age on workability, water absorption, mechanical, microstructure and interface characteristics. Results show that the incorporation of sulfate-eroded recycled aggregates increases the slump by up to 21.7%, and decreases the water absorption by approximately 9.9% given an erosion age of 126 days. With recycled aggregates under a long-term sulfate attack, the slump decreases and water absorption increases, which is due to the increased porosity of the attached old mortar on the recycled aggregate. Similarly, adding sulfate-eroded recycled aggregates leads to significant changes in compressive, split-tensile and flexural strength of concrete as well, with a sudden change occurring at an erosion age of 126 days. In addition, a large amount of erosion products, i.e., ettringite, remain in the residual mortar of the long-term eroded recycled aggregate, which results in excessive pore filling and causes more defects. Furthermore, it has a negative impact on the interface bond between recycled aggregates and the new mortar by reducing the proportion of C-S-H in the interface hydrates.