# Characteristics of Previous Concrete with Activated-Sludge Biological Fermentation
###### Abstract  
This study investigates the performance of sludge-added pervious concrete (SPC) at different curing temperatures by replacing some of the cement with activated sludge (AS). The results reveal that the incorporation of AS into pervious concrete had a favorable impact. At a curing temperature of 30 \({}^{\circ}\)C, the 28-day compressive strength and specific surface area reached 20.8 MPa and 9.14 m\({}^{2}\)/g, respectively, representing a 60% and 98.7% increase, in comparison to conventional concrete. Furthermore, the addition of AS to the concrete results in a notable reduction in the concentration of chemical oxygen demand (COD) in surface runoff water. The maximum rate of COD removal observed was 55.6%. A mechanism study revealed that the strength of concrete increased due to the reaction between reactive SiO\({}_{2}\) in AS and CaO in the aggregate. At a temperature of 30 \({}^{\circ}\)C, the microorganisms in the activated sludge fermentation process exhibit a higher production rate of fermentation gas, resulting in a greater escape of gas and an increase in the number of micropores in the permeable concrete. This leads to an enhanced specific surface area, which in turn exhibits a superior adsorption effect on COD. activated sludge; pervious concrete; curing temperature; specific surface area; runoff treatment +
Footnote †: journal: Applied sciences  
0000-0002-4300-3330]Xuechen Jia  
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human health [10; 11; 12]. Various methods for treating sludge have been proposed by scholars. [PERSON], [PERSON] et al. [13] prepared sintered bricks by mixing tannery lime sludge with clay. The compressive strength of the bricks met building standards. [PERSON] et al. [14] produced lightweight aggregates that met international standards by utilizing sewage sludge. These scholars used sludge as a construction material to gain insight. The above studies on the use of sludge conditioned into construction materials have saved investment costs and sludge treatment costs. However, the utilization of sludge is not comprehensive enough, especially the utilization of the microbial and organic parts of sludge. These two components are the two outstanding characteristics of sludge compared to other wastes. Our team is also currently exploring potential solutions to address this issue. According to this research, we used AS to replace a portion of the cement in the PC. The utilization of the abundant microbial community present in the AS [15] resulted in an increase in the specific surface area of PC through microbial fermentation. This process enhanced the adsorption capacity of PC and improved its ability to remove pollutants from stormwater. This method can not only utilize the inorganic components in sludge as a substitute for cement, but the utilization of microorganisms and organic matter has also been taken into account, which has some research value. The activity of microorganisms in AS [16; 17; 18] and the performance of concrete can be significantly impacted by temperature. The efficiency of fermentation is directly affected by microbial activity, which consequently modifies the specific surface area of pervious concrete. The objective of this study was to investigate the principle of microbial action on pervious concrete pore-making fermentation in sludge and to ascertain the effect of fermented concrete on the removal of organic pollutants in runoff stormwater. Therefore, the main objective of this study is to investigate the performance of AS-added pervious concrete (SPC) at different curing temperatures. Specifically, this study aims to detect the 7-day and 28-day compressive strength, the specific surface area, and the chemical oxygen demand (COD) removal percentage of SPC. In addition, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and Scanning Electron Microscopy (SEM) are used to reveal the principles of SPC from a microscopic aspect.