High-performance artificial aggregate prepared with recycled concrete powder and its impact on concrete properties

Given the pollution of waste concrete powder, low utilization rate, sand and stone resources shortage, and poor performance of artificial aggregate, the high-performance artificial aggregate was prepared by high dosage recycled concrete powder (RCP). The effects of curing methods, RCP grinding time, RCP:slag ratio, Na2O dosage, and Na2SiO3 modulus on the properties of the aggregate were studied. The results show that natural curing is the most effective, and the best-performing aggregate was obtained with an RCP grinding time of 40 min. The particle size coefficient of the aggregate was around 1.3, and increasing the proportion of slag increased the content of large particles. The amounts of slag and Na2O had a significant impact on the aggregate. As the amounts of slag and Na2O increased, the amount of C-(A)-S-H gel increased, the microstructure improved, and the macroscopic manifestations increased apparent density and strength and reduced water absorption. The maximum strength of the aggregate reached 8.59 MPa, and water absorption was 12.67% at this point. Concrete was prepared using the aggregate above, and the effects of aggregate curing time, aggregate pre-wetting time, and aggregate material ratios on the properties of the concrete were studied. The results show that the density of RCP artificial aggregate concrete is low, between 2030 kg/m3-2220 kg/m3. The compressive strength and splitting tensile strength of concrete increase with the increase of aggregate curing time, prewetting time, and the dosage of aggregate Slag and Na2O, which reach 59 MPa and 4.5 MPa, respectively. The aggregate strength increased, leading to interfacial failure inside the concrete, while larger aggregate particle size tended to cause aggregate failure inside the concrete.