Properties of RCA stabilized with alkali-activated steel slag based materials in pavement base: Laboratory tests, field application and carbon emissions

The extensive use of traditional binders (cement/lime) has caused serious resource consumption, environmental degradation, and carbon emission issues. Recycling industrial waste as a novel waste-based binder is a promising alternative. This paper purports to effectively stimulate the activity of steel slag (SS) and develop a novel eco-friendly pavement base mixture (NEPBM). A series tests of microscopic characterization, unconfined compressive strength (UCS), splitting strength (STS), freeze-thaw cycles, shrinkage, and field application were conducted to evaluate the performance of recycled concrete aggregate (RCA) pavement bases stabilized with alkali-activated SS based material (denoted as ACM). The results show that the potential activity of waste SS is strongly activated by alkaline activators, and the depolymerization-diffusion-polymerization reaction occurs to generate abundant additional gel products, thus the strength of ACM at 28-day reaches to 45.24 MPa. The mixtures with 50% ACM substitution rate is close to the control group in performances of UCS, STS, and resistance freeze-thaw cycle. The decrease (12.1 ×10−6) of dry shrinkage coefficient is far higher than the increase (1.11 ×10−6·℃−1) of temperature shrinkage coefficient, which effectively reduces the risk of early cracking. The field application indicates that the UCS of NEPBM at 7-day reaches to 4.26 MPa, which meets the technical requirements for heavy traffic of classⅠhighways in China, the construction cost of NEPBM reduces to 15.72 USD/m3, and the CO2 emissions reduces to 31.335 kg/m3. The results show that using NEPBM as a pavement base is a viable solution, which will be conducive to promoting the development of transportation infrastructure with excellent shrinkage performance and lower carbon footprint emissions.