## 1 Introduction  
Early strength concrete is used as an elemental technology for reducing construction time by realizing early formwork removal at construction sites [1, 2]. Early strength concrete can be investigated via two methods: (1) Appropriate management of the proportions of materials mixed in the concrete, and (2) acceleration of cement hydration by varying the curing temperature [3, 4]. It is possible to decrease the setting time of concrete and increase the curing speed by reducing the water to cement (W/C) [5]. For mixtures used in the field, a reduction in the W/C ratio increases the design strength by increasing the unit weight of cement. This method can improve the strength of concrete in a certain range when applied to the mixture design of a site. However, the method does not consider economic efficiency and cannot be used to improve concrete mixture design [6]. Ordinary Portland cement (OPC) is commonly used in concrete mixtures owing to its chemical stability. However, it exhibits limitations in terms of developing early strength in concrete [7]. Early strength in concrete can be developed using early strength cement, which increases the C\({}_{3}\)S content and fineness and decreases the C\({}_{2}\)S content; thus, for early strength development, early strength cement is better than OPC [8]. Despite the excellent early strength development, the early strength cement has not been commonly used because it is difficult to develop a stable long-term strength, hence reducing the economic efficiency. [PERSON] et al. [9; 10; 11; 12; 13] reported that a higher W/C ratio may have a greater influence on the early strength development and cement with a higher fineness can reduce the formwork removal time under the curing conditions at actual construction sites. It is possible to develop the early strength of cement for which the fineness of OPC is increased to 380 m\({}^{2}\)/kg, and the SO\({}_{3}\) content is increased to 3.1% in the scope of the 13-20 \({}^{\circ}\)C temperature range [14; 15]. [PERSON] et al. [16; 17; 18] conducted research on the early strength development of OPC by reducing the setting time using triethanolamine (TEA). Further, according to the research results reported by [PERSON] et al. [19], rapid curing occurred when the TEA accelerating agent was used in large quantities. A retarder was also used to control the rapid curing. However, the chemical decomposition of the accelerating agent and retarder was also reported in some cases. These studies have low reproducibility for the actual production of concrete, and they also have limitations in determining economical mixtures by fully considering the climate conditions of local areas. In particular, when the temperature of a local area is irregular and the curing temperature is less than 15 \({}^{\circ}\)C, accurate strength prediction for determining the formwork removal time [20; 21; 22; 23; 24] is difficult. In this study, we examined the influence of unit weight of cement in concrete that uses OPC on early strength development by considering the conditions of construction sites and referring to the concrete mixture of C24 (characteristic value of concrete, 24 MPa). In addition, high fineness and SO\({}_{3}\) OPC (HFS_OPC) and early Portland cement (EPC) were selected, for which the fineness and SO\({}_{3}\) content were varied considering the economic efficiency of mixture design. Further, the effect of the addition of a polycarboxylic (PC) superplasticizer mixed with an accelerating agent on the acceleration of early strength was analyzed. This study aims to examine the influencing factors of cement for early strength development by curing temperature and to develop the optimal mixture with economic efficiency. In addition, the formwork removal time was predicted, and its influence on the construction productivity was examined.