## 2 Testing Methods
### Mixture Proportion Design and Tests  
Because there are no standard designs for CLSM mixture proportions thus far, the current study used WFS as a fill material to replace 10% of the natural fine aggregates in the CLSM on the basis of a literature review. MSWI bottom ash was used to replace 0%, 25%, 50%, 75%, and 100% of the remaining natural fine aggregates. The design used a water-cement ratio of 1.6 and ages of 3 d, 7 d, 28 d, and 56 d. The mixture proportions are shown in Table 3.  
According to ASTM C143 [27] and ASTM D6103 [28], the slump should exceed 19 cm, with a slump flow of 40 cm and a tube flow ranging between 20 and 30 cm. As specified in ASTM C403 [29], the initial  
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**Properties** & **Sand** & **MSWI** & **WFS** \\ \hline Specific gravity (OD) & 2.573 & 2.002 & 2.561 \\ Water absorption (\%) & 2.564 & 11.179 & - \\ Moisture content (\%) & 2.05 & 4.25 & 44.5 \\ Fineness modulus (FM) & 2.979 & 2.86 & - \\ \hline \hline \end{tabular}
\end{table}
Table 1: Sand, municipal solid waste incinerator (MSWI), and water filter silt (WFS) physical properties.  
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**Chemical Compositions (\%)** & **Cement** & **MSWI** & **WFS** \\ \hline SiO\({}_{2}\) & 20.87 & 24.84 & 23.49 \\ Al\({}_{2}\)O\({}_{3}\) & 4.56 & 8.42 & 8.19 \\ Fe\({}_{2}\)O\({}_{3}\) & 3.44 & 30.63 & 18.18 \\ CaO & 63.14 & 27.8 & 38.8 \\ MgO & 2.82 & 1.5 & 1.7 \\ \hline \hline \end{tabular}
\end{table}
Table 2: Chemical compositions of Portland cement type I, MSWI, and WFS.  
Figure 1: Particle size distribution of municipal solid waste incinerator (MSWI) and sand materials.  
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**W/C** & **NO.** & **Cement** & **Sand** & **Water** & **MSWI** & **WFS** \\ \hline \multirow{4}{*}{1.6} & \multirow{4}{*}{WFS10} & M0 & 1378.9 & \multirow{4}{*}{350.2} & \multirow{4}{*}{292.1} \\  & & M25 & 1034.1 & & 292.1 \\ \cline{1-1}  & & M50 & 218.9 & 689.4 & 350.2 & 584.2 \\ \cline{1-1}  & & M75 & 344.7 & & 876.3 \\ \cline{1-1}  & & M100 & - & & 1168.4 \\ \hline \hline \end{tabular}
\end{table}
Table 3: Mixture proportions of controlled low-strength material (CLSM) (unit: kg/m\({}^{3}\)).  
setting time of a CLSM is when the resistance to penetration exceeds 2.74 MPa. The ball drop value was obtained from ASTM D6024 [30]. A free-fall heavy ball was used to impact the specimen; this process was repeated five times. The diameter of the indent area on the specimen surface was measured; the indent diameter D should be less than 7.6 cm. According to ASTM D4832 [31], the compressive strength on Day 28 of curing should not exceed 8.4 MPa. Ultrasonic pulse velocity was tested using the approach described in ASTM C597 [32] to measure the internal density of the specimen and to ascertain the effect of age on the specimen. Water absorption was examined according to the procedures of ASTM C642 [33]. Specifically, a specimen cured for 28 d was soaked in water for a day, removed, and dried with a dry cloth before it was weighed. Subsequently, the specimen was dried in an oven for 24 h before being removed and weighed again. Following the ASTM C373 [34], the porosity of the CLSM specimen was calculated by determining the volume of the specimen, which is based on its weight in water and its wet weight in the atmosphere after being in water for 24 h on Day 28 of the curing process. Regarding sulfate attack, procedures described in ASTM C1012 [35] were adopted; specifically, on Day 28 of the curing process, the specimen was dried in an oven for a day and then immersed in sulfate for another day (both steps constituted a cycle); this process was repeated for five cycles, after which weight loss and changes in appearance were examined.