# Effect of Super Retarder on Recycled Water and Concrete Properties of Waste Slurry in Mixing Plant
## 5 Conclusions  
The paper discusses a method for managing waste slurry water generated in concrete mixing plants by developing a super retarder using composite technology. The waste slurry water was mixed with a super retarding agent, characterized through X-ray diffraction (XRD), thermogravimetric (TG), and differential thermogravimetric (DTG) analyses. The treated waste slurry water was used in place of tap water for concrete production. The study evaluated the impact on concrete workability and mechanical properties. Based on the presented results of the experimental research, we can draw the following conclusions:  
The super retarder can retard the setting time of waste slurry recycling water under both single mixing and compounding conditions. Under single mixing conditions, SDP-90, ACS, PBTCA retardation effect is better, HEDP-4 Na and IDS retardation effect is general, AA/AMPS and PAPEMP retardation effect is worse. Compared with single blending, when PBTCA and ACS were blended, the setting time of waste slurry recycled water was more significantly retarded. There are good and bad types of compounding super retarder, among which, when PBTCA is compounded with ACS, it is favorable to the working and mechanical properties of concrete, the optimal ratio is 1:20, and the optimal mixing amount is 1.5% of the mass of recycled water of waste slurry. The microscopic study found that the types of crystal phases in the hydration products of cement at all ages in the waste slurry recycled water did not change after the incorporation of the blended super retarder of PBTCA and ACS. Combined with the thermogravimetric curve analysis, the use of super retarder blended with PBTCA and ACS only affects the rate of generation of hydration products, and has no effect on the types of cement hydration products. After mixing the super retarder compounded with PBTCA and ACS, the waste slurry recycled water replaces the mixing water for concrete production, which can effectively improve the workability and mechanical properties. When PBTCA:ACS reached 1:20, there was no loss of 1 h slump and the loss of 1 h extensibility was 15 mm. The 7 days compressive strength increased by 3.5 MPa and the 28 days compressive strength increased by 3.0 MPa relative to the reference group. J.W. : Writing-original draft, Validation, Methodology, Investigation. Y.Z. : Writing-review & editing, Supervision, Funding acquisition. L.G. : Supervision, Methodology. S.L. : Investigation. G.Y. : Investigation. All authors have read and agreed to the published version of the manuscript. This research was funded by The Fundamental Research Funds for Central Universities (ZY20190101). \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Serial Number** & **45–400 \({}^{\circ}\)C** & **400–540 \({}^{\circ}\)C** & **540–900 \({}^{\circ}\)C** & **CSH and AFt** & **CH** & **Total Combined Water** \\ \hline blank—1 day & 5.22 & 2.56 & 2.94 & 6.20 & 13.82 & 9.56 \\ blank—3 days & 7.65 & 3.64 & 3.51 & 8.82 & 18.90 & 13.42 \\ blank—7 days & 17.12 & 3.14 & 2.16 & 17.84 & 15.33 & 21.57 \\
0.5\%—1 day & 1.75 & 0.30 & 1.50 & 2.25 & 2.92 & 2.96 \\
0.5\%—3 days & 3.22 & 0.65 & 1.95 & 3.87 & 4.86 & 5.05 \\
0.5\%—7 days & 8.20 & 3.76 & 3.25 & 9.28 & 19.10 & 13.93 \\
1.5\%—1 day & 2.37 & 0.24 & 1.65 & 2.92 & 2.84 & 3.61 \\
1.5\%—3 days & 3.33 & 1.02 & 2.18 & 4.06 & 6.64 & 5.67 \\
1.5\%—7 days & 2.64 & 0.30 & 2.65 & 3.52 & 4.20 & 4.55 \\
2\%—1 day & 1.90 & 0.15 & 1.65 & 2.45 & 2.47 & 3.05 \\
2\%—3 days & 1.79 & 0 & 1.65 & 2.34 & 1.85 & 2.79 \\
2\%—7 days & 1.94 & 0.13 & 2.19 & 2.67 & 2.99 & 3.40 \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Amount of chemically bound water and calcium hydroxide (%) in the hydration products of each specimen. **Institutional Review Board Statement:** Not applicable. **Informed Consent Statement:** Not applicable. **Data Availability Statement:** The data presented in this study are available upon request from the corresponding author. The data set and code cannot be shared due to specific reasons.