UNIAXIAL COMPRESSIVE STRESS-STRAIN BEHAVIOUR OF RECYCLED AGGREGATE CONCRETE PREPARED WITH CARBONATED RECYCLED CONCRETE AGGREGATES

The influences of carbonated recycled concrete aggregate (CRCA) on the stress-strain behaviour of recycled aggregate concrete (RAC) were studied. Recycled concrete aggregate (RCA) pre-soaked in limewater was processed by accelerated carbonation for 24 h, whose pressure was 0.30 MPa. Four substitution ratios (0%, 30%, 70%, 100%) of the aggregate were utilised. RMT-150C rock mechanics test system (frame stiffness of 5 MN/mm, loading rate of 0.005 mm/s) was used to conduct the tests. The results showed that the failure modes of all specimens were shear failure, but the failure angles of RAC and CRAC (RAC prepared with CRCA) were larger than those of natural aggregate concrete (NAC), which were in the range of 63 degrees-75 degrees and 58 degrees-64 degrees respectively. As the substitution ratio of RCA increasing, the stress-strain curve of RAC gradually flattened, which meant its brittleness decreased. Moreover, its peak stress, elastic modulus, and peak strain decreased continuously, while its ultimate strain increased continuously. Compared with RAC, CRAC showed the similar stress-strain curve, but its brittleness was slightly higher. Furthermore, its peak stress, elastic modulus, and peak strain increased, while its ultimate strain decreased. Finally, based on linear regression analysis and relevant standards, the prediction models of peak stress, elastic modulus, peak strain, and ultimate strain, as well as the stress-strain constitutive models of RAC and CRAC were proposed, which had a good applicability to the test data. In conclusion, the stress-strain behaviour of CRAC were similar to that of RAC.