## 2 Materials and Mix Proportions
### Mix Proportions  
In concrete pavement repairs using rapid-hardening cement, a minimum of 4 h of curing time is specified as the traffic open time by the American Association of State Highway and Transportation Officials (AASHTO), the road traffic administration of each state in the United States, and the Korea Expressway Corporation [28; 29]. The traffic open standards are as follows: a compressive strength \(\geq\)21 MPa and a flexural strength \(\geq\)3.5 MPa. Furthermore, the splitting tensile strength was set at 3.2 MPa or more in this study. After 28 days of curing, the compressive strength should be \(\geq\)35 MPa and the flexural strength \(\geq\)4.5 MPa, with a splitting tensile strength \(\geq\)4.2 MPa. As such, the guidelines given were set at the mix goals of our study, as the intention was to apply the rapid-hardening cement to concrete pavement repair. Durability measures were based on water and chloride ion penetration test results, which have the biggest influence on a concrete pavement's usage life degradation. The chloride ion penetration amount was assessed according to the ASTM C 1202 test method [30], based on the standards of the Korea Expressway Corporation. The goal was \(\leq\)2000 Coulombs after 28 days of curing [29]. In this study, to ensure initial durability, the goal of chloride ion penetration at 4 h of curing was set at 4000 C or less. The target slump value was aimed at less than 40 mm, which is applied to concrete pavement mixture of Korea Highway Corporation, Keyongnam, Korea [31]. To achieve these goals, the mix had a water-to-cement (W/C) ratio of 0.28. Latex was added in at 5% of the cement weight. For the reinforcement fiber, 0.10% each of the synthetic macro fiber, natural jute fiber and PVA fiber were mixed. The mix ratios used are shown in Table 6.  
The cement, fine aggregate and coarse aggregate were added to the mixture. After this, the mixture was subjected to a mixing for 1 min and 30 s, followed by addition of water, which was mixed for 30 s. Following this, the fiber was placed and mixing was performed, before the latex was finally added. The addition of latex can increase the slump initially and increase the fiber dispersion effect. However, loss of slump occurs when fibers are dispersed. In order to improve the dispersibility of the fibers, mixing was conducted for 1 min and 30 s after the fiber was added. Further, after the addition of the latex, additional mixing was performed for about 1 min and 30 s.  
\begin{table}
\begin{tabular}{c c c c c c c} \hline
**Solids** & **Styrene** & **Butadiene** & **Specific** & **Surface Tension** & **Particle** & **Viscosity** \\
**Content (\%)** & **Content (\%)** & **Content (\%)** & **Gravity** & **(dyne/cm)** & **Size (Å)** & **(cps)** \\ \hline
30 & \(34\pm 1.5\) & \(66\pm 1.5\) & 11.0 & 1.02 & 30.57 & 1700 & 42 \\ \hline \end{tabular}
\end{table}
Table 4: Properties of styrene butadiene latex.  
Figure 1: Geometry of fibers. (**a**) Jute fiber; (**b**) PVA fiber; (**c**) Macro synthetic fiber.  
\begin{table}
\begin{tabular}{c c c c} \hline
**Properties** & **Synthetic Macro Fiber** & **PVA Fiber** & **Natural Jute Fiber** \\ \hline Elastic modulus (GPa) & 10 & 45 & 61 \\ Density (g/mm\({}^{3}\)) & 0.91 & 1.26 & 1.26 \\ Fiber length (mm) & 30 & 6 & 3 \\ Fiber diameter (mm) & 1 & 0.015 & 0.015 \\ Tensile strength (MPa) & 550 & 1600 & 510 \\ \hline \end{tabular}
\end{table}
Table 5: Properties of fibers.