The construction and demolition waste generation is increasingly evolving with the rapid urbanization, with more than a quarter of the produced waste being landfilled without further treatment or recycling strategy. Hence, sustainable management and valorization methods such as recycling in construction materials is becoming increasingly essential to tackle the economic and environmental burdens of landfilling waste. Construction and demolition waste recycling has been intensively studied. However, the present study proposes a promising solution for recycling construction and demolition wastes (CDWs) from the precast concrete waste sludge and ashes from paper mill sludge and biomass. Artificial lightweight aggregates were designed and produced by alkali activating a mixture of 50–90 wt% of dried and milled CDW with 3–25 wt% of ash and 5–35 wt% of blast furnace slag. The properties of the produced aggregates were assessed via density, water absorption, porosity, and crushing tests, in addition to microstructural characterizations using XRD and scanning electron microscopy SEM analysis. The optimum NaOH concentration was 8M with the highest mechanical properties and lowest efflorescence. The produced aggregates revealed a high crushing force of 82 N at 28 days with 50 wt% CDW, 15 wt% biomass ash, and 25 wt% blast furnace slag presenting a possible recycling pathway for such side-stream materials.
There is a growing need to find ways to reuse fine concrete waste from the construction industry. In this study, recycled concrete fines were granulated and used as lightweight aggregates. Ladle slag, a steel industry residue, was used as a co-binder in different ratios (0, 10, 20, and 30%). The materials were blended and granulated, and then the granules were cured in three conditions: ambient condition, humidity chamber, and carbonation chamber. The results showed that the ladle slag content of 30% cured in a humidity chamber produced the strongest granules, with a crushing strength of 127 N, which was 135% greater than a commercial lightweight aggregate. The granules generally had satisfactory density and water absorption with a higher ladle slag content. Carbonation increased the granule strength with a low ladle slag content and decreased the granules’ water absorption. The improved physical and mechanical properties of carbonated granules are attributed to the formation of calcium carbonate during the carbonation process. The granules produced in this study show good potential for use as lightweight aggregates in the construction industry. Graphical abstract
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