Optimizing concrete rheology to mitigate aerosol pollutants in wet-mix shotcrete processes

Abstract

Studies focusing on optimizing the pumpability and sprayability of concrete exist; however, research addressing the control of aerosol pollutants during the spraying process is limited. This study investigated the intricate relationships among additive formulations, rheology properties of fresh mixes, and aerosol pollutant emissions using a Box–Behnken design, combined with response surface methodology and gray correlation coefficient analysis. The developed high-accuracy regression model offers valuable insights into the impact of water-reducing agents (WRA), air-entraining agents (AEA), thickening agents (TA), and defoaming agents (DA) on the zeta potential, slump, surface tension of fresh mix concrete, and spread angle during wet-mix shotcrete (WMS), with R2 values of 0.94, 0.95, 0.95, and 0.95, respectively. Additionally, by considering both sprayability and a low spread angle, this approach facilitated the development of an optimal composite incorporating 1.36% WRA, 1.50% AEA, 0.20% TA, and 1.00% DA, yielding desired properties, including a slump of 200mm, spread angle of 20°, and aerosol pollutant concentration of 21mg/m3. This study provides a model to aid the formulation of shotcrete that mitigates aerosol pollutant generation during the WMS process, thereby contributing to the broader objectives of environmental sustainability and workplace safety.