Calcium dissolution behaviors of recycled coarse aggregate concrete with the initial stress damage

Abstract

The accelerated calcium dissolution tests of concrete with different replacement rates of recycled coarse aggregate (RCA) and different initial damage degrees D0 were carried out by using ammonium chloride solution. The results show that the dissolution resistance of recycled aggregate concrete (RAC) is negatively correlated with the replacement rate of RCA and the D0. The mass loss, dissolution depth, the attenuation of ultrasonic wave velocity, and the degradation of mechanical properties (compressive strength and splitting tensile strength) of RAC after calcium dissolution increase with the increasing replacement rate of RCA. When the D0 is less than 0.2, the dissolution resistance of RAC is not obviously affected by the initial stress damage; however, when the D0 is greater than 0.2, the mass loss, dissolution depth, the attenuation of ultrasonic wave velocity, and the deterioration of mechanical properties of RAC increase linearly with the increasing of D0. Compared with the compressive strength, the splitting tensile strength is more sensitive to the calcium dissolution and the initial stress damage of concrete. An obvious pH gradient is formed in the concrete after dissolution, and the pH value in a certain depth of the concrete decreases with the increasing of the replacement rate of RCA and the D0. Finally, the prediction model for compressive strength and splitting tensile strength of RAC after calcium dissolution is established.