## 3 Numerical and Experimental Verification
### Experimental Verification  
The specimens were made of concrete with a compressive strength of 27 MPa. The adopted cement was Type-I OPC with a Blaine fineness of 3414 cm\({}^{2}\)/g and density of 3.15 g/cm\({}^{3}\). The fly ash of Class F type as defined in [41] and the ground granulated blast-furnace slag (GGBFS) powder was also introduced. The density and surface area of fly ash were 2.13 g/cm\({}^{3}\) and 3850 cm\({}^{2}\)/g, respectively, and those of GGBPS were 2.89 g/cm\({}^{3}\) and 4330 cm\({}^{2}\)/g, respectively. Natural sand and crushed limestone with a maximum particle size of 5 and 25 mm, respectively, were used as the fine and coarse aggregates. Products with SiO\({}_{2}\) content larger than 98% were adopted as aggregate. Fly ash and GGBFS were admixed at weight ratios to binder of 15% and 25%, respectively. The water-to-binder ratio was 0.45. Polycarboxylate polymers were also adopted as superplasticizer to secure the workability of fresh concrete and provided a slump of 150 mm. Table 3 arranges the mixture proportions and properties of concrete. Two specimens were fabricated with anchors embedded to depths of 100 and 200 mm according to the conditions mentioned above. The dimensions of the concrete specimens were 500 \(\times\) 500 \(\times\) 500 mm\({}^{3}\) and the exposed length of the anchor was 100 mm. In addition, the two specimens were fabricated to have different cover thicknesses of 100 and 200 mm on their sides. Figure 9 shows a photograph together with the details of the specimens. The designation of the specimens for each considered case was the same as that in the numerical verification. Figure 8: Effect of the regularization factor on the transferred distance of the ultrasonic pulse through the embedded anchor bolt. \begin{table}
\begin{tabular}{c c c c c c c c c} \hline  & \multicolumn{3}{c}{**Mixture Proportion (kg/m\({}^{3}\))**} & \multicolumn{3}{c}{**Fresh Concrete**} & **Hardened Concrete** \\ \hline  & \multicolumn{3}{c}{**Binder**} & \multicolumn{1}{c}{**Fine**} & **Conse** & **SIP** & **Siump** & **Air Content** & **Compressive** \\ \hline
**Cement** & **Fly Ash** & **GGBFS \({}^{*}\)** & **Agg** & **Agg-** & **SIP** & **(mm)** & **(5s)** & **Strength \({}^{**}\)** \\ \hline
255 & 56 & 94 & 167 & 827 & 932 & 3 & 150 & 4.5 & 2\({}^{\prime}\) \\ \hline \multicolumn{8}{c}{\({}^{*}\) Ground granulated blast–furnace slag. \({}^{**}\) Compressive strength at age of 28 days.} \\ \end{tabular}
\end{table} 
Table 3: Mixture proportions and properties of fresh and hardened concrete. The travel time of the ultrasonic pulse was measured using the Ultracon-170 ultrasonic detector developed by MKC Korea. The ultrasonic transducer has a transmission pulse frequency 52 kHz and the travel time was acquired with a resolution of 0.1 \(\upmu\)s. A thin layer of petroleum jelly was used at the interface between the transducers and specimen to dispel air between them. As shown in Figure 9, the transmitter was disposed at the head of the exposed part of the anchor and the receiver was displaced sequentially downward from the top of the concrete to measure the arrival time of the ultrasonic pulse. Figure 10 shows the measured and theoretically calculated values for the arrival time of the ultrasonic pulse in each specimen. As shown in Figure 10a, as the distance of the receiver from the top surface of concrete increased, the arrival time of the ultrasonic pulse gradually lengthened because the transferred distance of ultrasonic pulse through the concrete and anchor bolt increased. When the receiver was located on the upper part of concrete, the arrival time of ultrasonic pulse was dominantly influenced by the cover thickness, and the values were almost similar regardless of the embedment length of the anchor bolt in the case of the same cover thickness. However, as the location of the receiver became further from the top of the concrete, there was a clear difference in the arrival time of the ultrasonic pulse due to the difference in the embedment depth of the anchor bolt.