## 2 Raw Materials and Test Methods
### Test Methods
#### 2.3.2 Performance Test  
The freeze-thaw test was conducted using the DTR-1 concrete rapid freeze-thaw testing equipment. Following the \"rapid freezing method\" outlined in the long-term performance and durability standard of ordinary concrete (GB/T 50082-2009) [18], the freezing and melting temperatures of the specimens were set at (\(-17\)\(\pm\) 2) \({}^{\circ}\)C and (8 \(\pm\) 2) \({}^{\circ}\)C, respectively. The melting stage was maintained for not less than one-fourth of the entire freeze-thaw cycle, and each cycle lasted for 2-4 h.  
The change in specimen mass after freeze-thaw was measured using an electronic balance with a precision of 0.1 g. The mass variation rate can be calculated using Equation (1).  
\[M=\frac{m_{0}-m_{t}}{m_{0}} \tag{1}\]  
where \(m_{0}\) is the initial mass of sample (g); \(m_{t}\) is the mass of the sample after the freeze-thaw cycles (g); and \(M\) is the mass variation of the concrete.  
The non-metallic ultrasonic testing and analysis instrument NM-4B was used to determine the ultrasonic wave velocity. The relative dynamic elastic modulus of concrete  
\begin{table}
\begin{tabular}{c c c c c c c c c c c c c} \hline \hline \multirow{2}{*}{**No.**} & \multicolumn{6}{c}{**Materials, kg-m\({}^{-3}\)**} & \multirow{2}{*}{**W/B**} & \multirow{2}{*}{**JM-B**} & \multirow{2}{*}{**Steel**} & \multirow{2}{*}{**Elasticity**} & \multirow{2}{*}{**Sump, **Mobile**} & \multirow{2}{*}{**Amm**} & **Aix** & **28-Day** \\  & & & & & & & & & & & & **Compressive** \\  & & & & & & & & & & & & **\%** & **Strength** \\ \hline HSC-1 & 600 & 0 & 610 & 1134 & 150 & 0.25 & 3.9 & 0 & 0 & 50 & 1.9 & 45.1 \\ HSC-2 & 540 & 60 & 610 & 1134 & 150 & 0.25 & 3.9 & 0 & 0 & 45 & 1.8 & 59.3 \\ HSC-3 & 600 & 0 & 785 & 957 & 150 & 0.25 & 5.0 & 156 & 0 & 40 & 2.3 & 70.7 \\ HSC-4 & 600 & 0 & 785 & 957 & 150 & 0.25 & 6.5 & 0 & 1 & 50 & 3.1 & 62.3 \\ HSC-5 & 540 & 60 & 785 & 957 & 150 & 0.25 & 5.0 & 156 & 0 & 45 & 2.2 & 84.3 \\ HSC-6 & 540 & 60 & 785 & 957 & 150 & 0.25 & 6.5 & 0 & 1 & 45 & 3.2 & 69.1 \\ \hline \hline \end{tabular}
\end{table}
Table 2: Mixture proportions and performance of different concrete.  
during freeze-thaw cycles was calculated based on the proportional relationship between the dynamic elastic modulus and the square of ultrasonic wave velocity, as specified by the following formula [19]:  
\[E_{r}=\frac{E_{t}}{E_{0}}=\frac{V_{t}^{2}}{V_{0}^{2}} \tag{2}\]  
where \(E_{r}\) is the relative dynamic elastic modulus; \(E_{0}\) and \(V_{0}\) are the initial dynamic elastic modulus and ultrasonic wave velocity of the concrete before experimentation; \(E_{t}\) and \(V_{t}\) are the dynamic elastic modulus and ultrasonic wave velocity of the concrete after a certain number of freeze-thaw cycles. When the relative dynamic elastic modulus drops to 60%, or the mass loss rate reaches 5%, it is considered that the concrete has undergone freeze-thaw damage. At this point, the corresponding number of freeze-thaw cycles is identified as the freeze-thaw life of the concrete. The relationship between the relative dynamic elastic modulus and the number of freeze-thaw cycles can be determined by using spline interpolation.