Sustainable reuse of excavated soil and recycled concrete aggregate in manufacturing concrete blocks

This paper investigates the properties of concrete blocks manufactured with excavated soil (ES) and recycled concrete aggregates (RCAs). The influences of cement dosage and RCAs (or ES) content on the physical and mechanical properties of the concrete blocks were evaluated. Effects of water immersion and wetting–drying cycles on the compressive strength of the concrete blocks were also investigated, followed by a microstructural characterization on the reaction products. Finally, a cradle-to-gate Life Cycle Assessment (LCA) was conducted to assess the environmental benefits of the green concrete blocks. The results indicate that increasing either the cement dosage or the RCA content can improve the physical and mechanical properties of the concrete blocks. Concrete blocks with a higher cement content or RCA content show better water resistance and only 10% reduction in compressive strength after a 24-hour water immersion. Whereas, the compressive strength of ES-based concrete blocks is enhanced by 20% to 80% after exposing to wetting–drying cycles, particularly for those with a higher ES content. This is mainly attributed to the pozzolanic reaction of smectite in the ES, as evidenced by the enhanced cumulative hydration heat after the incorporation of ES as well as the reduced peak intensities of smectite and calcium hydroxide in XRD results. The LCA demonstrates that increasing the RCA content in concrete blocks increases the energy consumption and global warming potential, but decreases the saved land occupation and transformation. These findings open up new possibility to manufacture eco-friendly concrete blocks containing ES and RCAs considering their mechanical properties and environmental benefits.