Chloride transport and thermoactivated modification of sustainable cement-based materials with high-content waste concrete powder

Reusing high-content ground waste concrete powder (WCP) as eco-friendly binder promoted the recycling of construction and demolition waste, but previous studies rarely considered the chloride transport in cement-based materials with high-content WCP. Therefore, this work investigated the chloride transport and thermoactivated modification of high-content WCP blended mortar, and WCP was divided into WCPP and WCPC ground from cement paste waste and concrete waste, respectively. Mixing high-content WCP negatively impacted the micro-characteristics of blended paste. But new calcium oxide and C2S/C3S were generated in heat-modified WCP, and the micro-structure of heat-modified WCP blended paste was finer than the micro-structure of un-modified WCP blended paste. The average pore diameter of paste with 50% 800°C-modified WCPP and WCPC was 33.5% and 38.7% smaller than that of paste with 50% un-treated WCPP and WCPC, and was 3.4% higher and 6.7% smaller than that of reference paste without WCP. Incorporating high-content WCP declined the mechanical strength and obviously raised the chloride transport in blended mortar. At equivalent replacement level, the chloride transport in heat-modified WCP blended mortar was lower than that in un-modified WCP blended mortar, and the reduction in chloride transport was more distinct as heat-modified temperature elevated. When the dosage of WCP is 50%, the maximum chloride content of mortar with 800°C-modified WCPP and WCPC was 27.5% and 22.7% smaller than that of mortar with un-modified WCPP and WCPC. Mixing 600 °C heat-modified WCPP or 800 °C heat-modified WCPC up to 50% can prepare sustainable mortar with superior strength and chloride transport resistance.