Methods of strengthening the grains of recycled aggregates

Abstract

Poorer quality indicators than natural aggregates generally characterize recycled aggregates. This is due to the composition of the primary raw material (mostly demolition waste), the method of processing (crushing, sorting) and the typical character of the grains, which, in addition to the original grain of natural aggregate, also contains the original adhered mortar. The resulting grains are heterogeneous, characterized by lower strength, higher porosity, higher absorbency, or the presence of cracks. Improving the quality of these grains is one of the approaches to increase their potential for use in concrete. Several methods of recycled concrete aggregate (RCA) grain strengthening are being studied worldwide, the effect of which on the final quality of recycled aggregates and new concrete is different. The article describes and compares the methods in terms of their impact on selected properties of both. The comparative analysis is based on the collection of results presented in research publications. Based on the evaluation of the results, polymer emulsion treatment can be identified as the most effective way to improve RCA water absorption. Sodium silicate treatment came out the best to improve the compressive strength of concrete mixed with treated RCA.