Fracture of Recycled Aggregate Concrete under High Loading Rates

Using renewed materials in the construction industry is very important for sustainable development. Recycled aggregate concrete (RAC) is one of the renewed materials. RAC uses demolished concrete as aggregate to make concrete. Previous studies showed that the strength of RAC can be improved and made comparable to regular concrete. This study examines the rate effect on fracture properties of RAC using an available improvement method. The RAC was made of 100% recycled coarse aggregate pretreated by a surface coating method. The fracture properties of RAC were tested based on the size effect method. Three different sizes of notched RAC beams were tested under three different strain rates, from 10(-5)/s to 10(-2)/s, controlled by crack-mouth-opening-displacement (CMOD). For the beams under high loading rates, the fracture properties were found to be rate-dependent. The critical stress intensity factor, K-Ic, and the fracture energy release rate, G(f), increase with increasing loading rate. Two empirical equations were proposed for K-Ic and G(f) as functions of the loading rate. Under high loading rates, the RAC beams were found to be less brittle than under the static load. This was also indicated by the test data of effective fracture process zone length, c(f), which increased with an increasing loading rate. (C) 2016 American Society of Civil Engineers.