Sustainable utilization of pretreated concrete waste in the production of one-part alkali-activated cement

A cleaner production of one-part alkali activated cement (AAC) was implemented by mixing chemically treated concrete waste (CTC) with slag. The treatment process was conducted by the addition of NaOH to concrete waste (CoW) at NaOH to CoW weight ratios of 0.2, 0.1, and 0.05 (namely, CTC-1. CTC-2, and CTC-3, respectively), followed by mixing with water and drying. The solidified material was ground then dry-mixed with slag to create one-part alkali AAC powder with fixed particle size. The amount of CTC was varied to achieve constant Na2O content (2 wt %) in all mixtures. The results indicated that the prepared one-part AACs can react with water to yield hardened materials with acceptable compressive strength. Comparing with CTC-1 and CTC-3, the CTC-2 was found to have a dominant impact on the activation of slag hydration, which associated with the higher mechanical properties, lower pore volume, and drying shrinkage. The addition of lead bearing sludge (LBS) to one-part AAC containing CTC-2 resulted in a positive impact on the performance of the prepared cement. According to toxicity characteristic leaching procedures the prepared cement showed a potential effect on solidification/stabilization of Pb-containing-sludge.