V. Bhasya, B. H. Bharatkumar
American Concrete Institute (ACI)
Admixtures; Concrete aggregates; Durability; Mechanical properties; Mortar; Recycled materials; Recycled concrete aggregate; Highways; Materials; Pavements
The presence of attached mortar is the main reason for lower quality of recycled concrete aggregate (RCA) compared to that of natural aggregate. Hence, its use is limited up to 30% replacement of natural aggregate at present. The attached mortar of the RCA can be removed by mechanical treatment, acid treatment, thermal treatment (500 to 750°C [932 to 1382°F]), and microwave treatment. There are difficulties—such as achieving high temperature and treating larger quantities of RCA with acid and a microwave oven—in applying these treatments at field level. Hence, the present study focuses on a combination of heating (250°C [482°F]) and mechanical treatment to improve the quality of the RCA. This method removed 70 to 80% of attached mortar of the RCA. Properties of RCA such as bulk density, specific gravity, water absorption, and crushing value were discussed in detail. Post-treatment, it was observed that the properties of treated RCA improved compared to untreated RCA, but still they were found to be poorer than natural aggregate. The experimental studies were carried out to overcome the aforementioned drawbacks of the recycled aggregate concrete by incorporation of mineral admixtures. It was found that the use of mineral admixtures in concrete produced with treated RCA enhances both the mechanical and durability properties. Thus, the concrete produced with treated RCA and mineral admixture will lead to sustainable development.