Effect of treatment types of recycled concrete aggregates on the properties of concrete

Reusing waste materials such as construction and demolition waste is an environmentally significant task. This article aims to improve the quality of recycled aggregates after the demolition of concrete structures. Two methods, mechanical cleaning and impregnation, were explored to enhance the quality of coarse aggregates. The findings indicate that mechanical cleaning is more effective than soaking in a sodium silicate solution. The compressive strength of concrete made with mechanically cleaned recycled aggregates was 2.3 times greater than that of concrete made with untreated rubble. Concrete with impregnated rubble had a compressive strength 1.1 times greater than that of concrete with untreated aggregates. Infrared spectroscopy was used to study the microstructure, revealing that the type of treatment does not influence the quantity of portlandite and ettringite in hydrated cement. However, the treatment of recycled aggregates alters the interaction in the gel portion of cement hydration products. Concrete with aggregates treated by sodium silicate has more aluminate components. Additionally, there is a shift of the bands assigned to Si-O stretching to higher wave numbers (from 995 cm–1 to 1088 cm–1), which can be attributed to the formation of calcium-silicate-hydrate gel with a lower calcium/silicon ratio.