Evaluation of the Freeze and Thaw Resistance of Recycled Concrete Aggregates and Natural Aggregates

In the last decade, structural waste-recycling and production of recycled concrete- aggregate has widely been considered as an environmental approach. The use of recycled aggregate, produced from recycling of demolished concrete in civil engineering projects, such as transportation projects, can have a major effect on providing sand and gravel sources and solving some of the environmental problems. One of the performance characteristics of these kind of materials is their durability against continuous freeze and thaw cycles. Destructions due to this cycle are one of the durability problems for different layers in pavements in cold climates. On the other hand, considering the share of aggregates in road construction, it should be noted that durability performance of these aggregates against freeze and thaw cycles is important in performance of the layers. Up to now, different standards have been written for durability assessment of the aggregates against freeze and thaw cycles. But, due to the difference in structure of recycled concrete aggregates (RCAs) and lesser quality of these aggregates, compared to the natural aggregates (NAs), application of these standards for RCAs is questionable. Therefore, in this research, three standards of ASTM C 88, AASHTO T 103 and CSA A23.2-24A were selected to assess the durability of RCAs and NAs against freeze and thaw cycles. Water adsorption and abrasion tests in Los Angeles apparatus were conducted too. Results showed that AASHTO test has high destruction power and its application with temperature-time cycle in this experiment is not recommendable. Also, the aggregate soundness test, using magnesium sulfate test, is not applicable for RCAs and does not have reliable results. But, the CSA test has acceptable results, in accordance with the results of physical and mechanical tests.