Study of waste-derived high-sulfate artificial aggregates with regenerative capacity

Abstract

To develop artificial aggregates (AAs) with potential for large-scale applications, this study focused on artificial high-sulfate aggregates (AHAs) with recycling capacity, prepared using various solid wastes, and a sulfate-resistant concrete system was designed. AHAs are prepared using a slurry consisting of ground granulated blast-furnace slag, steel slag powder, and phosphogypsum. Combining AHA and sulfate-resistant cement produces sulfate-resistant concrete. The results show that the produced aggregate is lightweight, and the PA-3 samples exhibit cylindrical compressive strength (10.77 MPa) close to that of natural aggregates. The PA-3 sample contains more C–S–H gels and has a denser structure owing to the formation of protofibrous ettringite at the appropriate Ca/Si ratio. Microanalysis of the mortar–aggregate interface in concrete reveals that S is the key element distinguishing the aggregate from the mortar. Moreover, the results indicate that some of the AHAs have regenerative capacity, and their waste can be reintroduced into aggregate production. This study aims to inspire research and development in the field of sulfate-resistant concrete systems and promote the wider use of AHAs in the concrete market.