42 / 2022-03-25 03:52:40

Resourceful treatment of recycled clay brick sands and its up-cycling utilization in photocatalytic mortar

Construction and demolition wastes, Recycled clay brick sands, Photocatalytic mortar

Billions of construction and demolition wastes (C&DW) are generated yearly in China; whilst most of them are landfilled, leaving a heavy burden on the natural environment, and causing a serious and irreversible impact upon surrounding water and air resources. Researchers thereby attempt to transform those C&DWs into recycled coarse aggregates that are expected to replace natural coarse aggregates in preparing new concrete. This kind of resourceful treatment however is not feasible for recycled clay bricks (RCB) that account for the second-largest proportion of C&DWs, attributing to the ultra-high porosity and low hardness of RCB. This study by that proposed an innovative approach to reuse RCB. The RCB was crushed and sieved into recycled clay brick sands (RCBS) ranging from 0.06-4.75 mm and then united with nano-scale titanium dioxides (NT) into composite photocatalysts (CP). The prepared CPs were then utilized as fine aggregates in the photocatalytic mortar (POM) for NOx removal. Results showed that the prepared POM could effectively abate NOx at low concentrations (~1000 ppb). Besides, once 25% RCBS-CPs were substituted by cullet-CPs, the synthetical degradation was boosted 18.9% whilst the cost was reduced by 80% relative to the traditional intermixing method with the NT content of 5 wt.% of the cement dosage. It was noteworthy that the combined use of RCBS-CP and cullet-CP was also conducive to the rheological behavior and the mechanical performance of end products. The coupling effect between RCBS-CP and cullet-CP was therefrom nominated. The paper at length established a mathematical model using the fuzzy interference system (FIS) and examined the influence of initial concentration (IC) and flow rate (FR) on the dynamic degradation of NOx.