Study on preparing process for a recycled concrete

Abstract The industrial waste like steel-slag, coal gangue and limestone were used to prepare high-strength aggregates with a composition like cement clinker in the present investigation, and the concrete were prepared by this aggregates rather than natural aggregates. The experimental results showed that this kind of concrete can be completely regenerated to be cement and used for building project again, so any construction waste were not produced, and the recycling of concrete can be truly realized. A tentative study of preparing a kind of recycled concrete was carried out, and the results showed that the aggregates with about 7% steel slag, 12% coal gangue, 80% limestone and calcined at 1400 °C had the best performance. The water absorption (about 0.82%), the crushing index (about 6.78%) and the apparent density (2672 kg/m3) of the aggregates meet the requirements of national standards (GB/T14685-2001). The concrete was prepared using these aggregates with the water-cement ratio of 0.45, the compressive strength of the concrete in 28 days is 58.7 MPa, higher than that of ordinary concrete. The waste of concrete after hardened of 90days were grinded and calcined at temperature of 1420 °C and the cenment clinker was prepared. After hydrated for 3 days, 7 days and 28 days, the compressive strength is 29.8 MPa, 45.1 Mpa, 51.3 Mpa, respectively, which reach the requirements of 42.5 ordinary Portland cement.