Basic mechanical properties test and stress-strain constitutive relations of recycled coarse aggregate concrete

Recycled coarse aggregate concrete(RAC) specimens were made by the waste concrete, whose original designing strength was C30, including 66 standard prism(150 mm×150 mm×300 mm) and 33 prism with the size of 150 mm×150 mm×550 mm. Using these specimens, the uniaxial compressive strength, flexural strength, elastic modulus and Poisson's ratios were determined. The basic mechanical properties of RAC under the different replacement rates were researched. Furthermore, based on the measured data, the stress-strain constitutive equation was estsblished. The results show that with the increase of recycled aggregate replacement rate, the prism compressive strength at the standard age is a little higher than that of the natural aggregate concrete(NAC), while RAC and NAC have a similar shape of whole stress-strain curves. In the rising stage of the curve, RAC and NAC have basically coincident curve, however, in descending stage, the curves of RAC are much steeper than NAC's. For the same batch of RAC at standard age, the ratio of flexural strength to prism compressive strength is about 0.12, and the average ratio of prism compressive strength to compressive strength of the cube is 0.87. The recycled coarse aggregate replacement rate does not have a large influence on the RAC's strength, and specimens' flexural strength and prism compressive strength with each replacement rate are close to those of NAC. The RAC's prism compressive strength with long time setting(2 a) is much higher than that of specimens at standard age, and after calculation, the growing rate reach to 16.87 percents. Comparing with the NAC, the RAC's elastic modulus with long age grows greatly, while the Poisson's ratios are relatively stable, furthermore, the values under the higher replacement rate are smaller than NAC' values.