Utilization of RCAs arising from excavated soil in CTBM: Laboratory characterization and environmental impact assessment

A large amount of excavated soil is generated due to rapid urban infrastructure development, resulting in serious safety and environmental threats. From the perspective of resource recycling, this paper conducted a laboratory characterization and environmental impact assessment of the utilization of recycled crushed aggregates (RCAs) arising from excavated soil in cement-treated base materials (CTBM). SEM-EDS was employed to test the chemical elements and surface properties, and it reflected larger pores and cracks compared to diabase and limestone aggregates. A series of experimental tests were carried out to investigate the mechanical behaviors of CTBM with varying cement content incorporating RCAs. The laboratory test results revealed that the UCS, IDT strength, FTS and CRM increased with increasing cement content. Moreover, an environmental impact assessment of the recycling of RCAs to produce CTBM was preliminarily analyzed compared to the traditional CTBM with natural stone aggregates (NSAs). The results showed that the attenuation in different environmental impact categories was more than 26% when recycling RCAs from excavated soil to replace NSAs. It was clear that the utilization of 1 t RCAs could result in a reduction of approximately 75 MJ in energy and 5.17 kg CO₂-eq in emissions just in terms of reducing transportation and landfill. Thus, a total reduction of 3.15 billion MJ energy and 21.72 million t CO₂-eq emissions could be realized if all the excavated soil generated in Shenzhen annually was recycled. Furthermore, possible policies and further prospects were suggested based on the research for more sustainable management of construction and demolition waste (CDW) containing excavated soil.