# Effect of Super Retarder on Recycled Water and Concrete Properties of Waste Slurry in Mixing Plant
## 1 Introduction  
Concrete, the most widely utilized construction material globally, produces substantial waste slurry water during its manufacturing process [1]. A concrete plant with an annual output of approximately 1.2 million cubic meters generates 60 tons of wastewater annually from cleaning equipment. This waste slurry water primarily originates from gravel separators, transportation trucks, production site rinsing water, and some rainwater. It contains a significant amount of cement, mineral powder, and fly ash, along with their hydration products, and its direct discharge leads to severe pollution of water resources and the environment [2, 3]. As modern industrialized production technology advances and societal demands for environmental protection escalate, people's awareness of sustainable development continues to grow. China faces a significant challenge due to its scarcity of water resources, making the judicious utilization of recycled water crucial for conserving water and protecting the environment. The treatment and application of recycled water in concrete mixing plants by ready-mixed concrete producers have garnered societal attention and are now considered a key metric for assessing the green credentials of mixing plants [4]. Consequently, it is imperative for enterprises to ensure that wastewater is treated to meet the established discharge standards before it is released from the mixing plant. After identifying the primary physical and chemical characteristics of waste slurry water, [PERSON] et al. [5] investigated the impact of each critical factor on the treatment of concrete effluent using single-factor experiments, orthogonal tests, and response surface methodology. They analyzed the effect and mechanism of influence of each factor at a micro level. [PERSON] et al. [6] investigated the effect of placing time of recycled slurry water with a concentration of 6.4% in mixing plant on the performance of concrete, and analyzed the changes of hydration products and microscopic morphology of recycled slurry water in cement slurry with different placing time by XRD and SEM. [PERSON]. [7] investigated the impact of varying dosages of plant wastewater (25%, 35%, and 45%) on the mass loss, appearance, dynamic elastic modulus, and compressive strength of concrete subjected to freeze-thaw cycles. Furthermore, a freeze-thaw damage model specific to concrete containing wastewater was developed. [PERSON] et al. [8] experimentally validated the mechanical and durability properties of concrete containing waste cement sludge and silica fume, and identified the optimal cement replacement rate. [PERSON] et al. [9] investigated the mechanical and durability properties of concrete prepared with wastewater and showed that the mechanical properties of concrete prepared with wastewater do not deteriorate, and even improve in terms of homogeneity, with no increase in the risk of corrosion. [PERSON] et al. [10] investigated the use of wastewater in mortar preparation and found that wastewater, when combined with CEM III/A 42.5 cement, was able to produce mortars with high-strength properties for a wide range of engineering environments. [PERSON] et al. [11] investigated the ideal pH range for concrete mixing water and found that a pH range of 7.2 to 7.6 slightly alkaline helps to ensure concrete stability. [PERSON] et al. [12] used different proportions of wastewater instead of tap water for concrete mixing, and found that wastewater concrete has better compressive properties than ordinary concrete, with 75% wastewater mixing increasing the compressive strength of concrete by about 20%, and the advantage is more obvious in the early age. In summary, domestic and foreign research on waste slurry recycled water is mostly focused on its use in the reproduction of concrete, and the impact of mixing waste slurry recycled water on the working performance, mechanical properties, durability performance of concrete, etc., and there are certain constraints.