Experimental investigation on properties of gold tailings recycled brick-concrete aggregate concrete under microwave curing

Tailings are the low-value solid waste by-products, which can be expected to serve as sustainable material through activation. In this study, activated gold tailings (GT) were utilized as supplementary cementitious materials to produce GT-cement slurry and gold tailings recycled brickconcrete aggregate (GT-RBCA) concrete. By varying curing methods including microwave curing and steam curing, the effects of resting time and curing temperature on compressive strength of GT-cement slurry specimens were experimentally analyzed. Also, X-ray diffraction (XRD) and scanning electron microscopy (SEM) were employed to analyze the hydration products and microstructure. Additionally, the compressive strength of GT concrete including GT-RBCA concrete under these curing methods were explored, followed by an assessment of environmental and economic benefits. The results demonstrated that a curing temperature around 40 degrees C with microwave method and 10%-20 % GT will benefit the strength development of GT-cement slurry specimens, reach the highest 28-day compressive strength of 42.6 MPa compared with steam curing and standard curing. This could be attributed to the "hot spot" effect of GT under microwave curing, leading to effective promotion of the pozzolanic reaction and subsequent enhancement of the hydration reaction. For GT-RBCA concrete, microwave curing exhibited the best effect on early compressive strength of GT-RBCA concrete compared with other curing methods. Particularly, whether the standard water-cement ratio condition (w/c = 0.42) or the low water-cement ratio condition (w/c = 0.35), GT-RBCA concrete under microwave curing at 40 degrees C and 10 % gold tailings substitution rate, achieved a maximum 12.3 % increase in 28-day compressive strength compared to steam curing and standard curing conditions. In addition, the GT-RBCA concrete under microwave curing obtained 11.7 % CO2 emissions reduction compared with steam curing.