# Suppression Effect of Waterborne Polymer on Soil Used for Backfilling at Construction Site
## 3 Results
### Effect of Dust Suppression at a Construction Site  
Large-scale dust suppression was conducted at a construction site in Hongqiao District, Tianjin, China, to prove the above laboratory results. As shown in Figure 6, the area was 20,000 square meters large, surrounded by roads on three sides and another construction site to the north. A waste soil yard at the north side of the construction site mixed with bricks and tiles was set as monitoring point C1. As the main dust suppression area, the bare ground and the soil of the backfilling yard at the west side (waste body: 60 m \(\times\) 200 m; maximum vertical height: 4.2 m) were set as monitoring points for fugitive dust C2, C3, and C4. The bare ground at the east was used as a control area, with monitoring points B1 and B2 for comparison. The particle concentration in the dust suppression and control areas was calculated as the average value of the monitoring points. At 13:00 h on June 26, 2017, the temperature was 35.6 \({}^{\circ}\)C, the relative humidity was 46.9%, and the speed of the southwest wind was 4.86 m/s. After using a mist cannon for spraying, the measured results were as follows: the mass concentration of the dust suppressants was 1.0%, the amount for the waste area was about 1.0 kg/m\({}^{2}\), and that for the ground was about 1.3 kg/m\({}^{2}\). The construction and water spraying were ongoing during the field dust suppression. According to Table 6, the dust concentration in the dust suppression area was similar to that in the control area before spraying (0 h).  
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**Items** & **Detection Limits** & **Specified Limits** & **Detection Results** \\ \hline Volatile organic compounds (VCCs)/g\(\cdot\)L\({}^{-1}\) & 2 & 120 & 3.24 \\ Totals of benzene, methylbenzene, ethylbenzene, and xylene/mg\(\cdot\)kg\({}^{-1}\) & 50 & 300 & Not detected \\ Free & 5 & 100 & Not detected \\ formaldehyde/mg\(\cdot\)kg\({}^{-1}\) & 1 & 60 & Not detected \\ \hline \hline \end{tabular}
\end{table}
Table 5: Contents of hazardous substances in dust suppressants.  
Figure 6: The layout of dust suppression areas at the construction site. C1 is the monitoring point. C2, C3 and C4 are monitoring points in the dust suppression area. B1 and B2 are the monitoring points in the control area.  
According to Figure 7a, the dust suppression efficiency for PM\({}_{10}\) 24 h after stabilization was 67.41%, exhibiting a difference of 11.54% from the estimated result, while that of PM\({}_{2.5}\) was 53.68%, differing from the estimated result by 25.27%. It can be concluded that the estimated results were in line with the actual results, and the performance evaluation method used in this paper was feasible, given the monitoring errors and differences in the temperature, humidity, and test conditions at the construction site.  
Since the construction site was fully open and the stable area was limited, the external factors greatly affected the dust suppression efficiency, which decreased continuously with time. The dust suppression efficiencies for PM\({}_{10}\) after stabilizations of 48 and 72 h were 60.87 and 46.54%, respectively, and the average dust suppression efficiency for PM\({}_{2.5}\) after 72 h was 50.18%. Figure 7b shows the surface state of the waste area on day 15 after stabilization, with a stable crusting effect and normal plant growth.