# Property Analysis of Slag Composite Concrete Using a Kinetic-Thermodynamic Hydration Model
## 1 Introduction  
Granulated blast furnace slag is a by-product of steel and iron manufacture and can be used as a mineral admixture for producing sustainable concrete. Slag composite concrete shows various advantages, such as good workability, high late-stage strength, good resistance to chloride penetration, and good appearance [1, 2]. In addition, slag composite concrete is a sustainable alternative because it has lower CO\({}_{2}\) emissions and the cost of materials is lower than plain concrete [2, 3, 4]. Numerous experimental and theoretical studies have been carried out to investigate the reaction degree, hydration heat, and strength of slag composite concrete. First, regarding experimental studies, [PERSON] and [PERSON] [5] found that the compressive strength of slag composite concrete has a strong linear relationship with hydration heat at the same age. [PERSON] et al. [6] and [PERSON] et al. [7] found that as the replacement percentage increases and the water/binder ratio decreases, the reaction degree of slag decreases. [PERSON] et al. [8] found that slag cement has a positive effect on late-stage strength and workability and a negative effect on the capillary absorption and salt scaling of ultra-high-performance concrete. [PERSON] et al. [9] found that 40% slag composite concrete showed a strength crossover, while 80% slag composite concrete did not show a strength crossover. [PERSON] et al. [10] found that 30% is the optimal replacement percentage of slag for producing high early-strength concrete. Second, regarding theoretical modeling, [PERSON] et al. [11] evaluated the compressive strength of slag composite concrete using a statistical model of the slag replacement ratio,curing temperature, water/binder ratio, and bound water content. [PERSON] et al. [12] evaluated the compressive strength of slag composite concrete using artificial neural networks. [PERSON] et al. [13] performed a second-degree regression of the 3, 7, 14, and 28-day strength of cement-slag-fly ash ternary composite. [PERSON] et al. [14] proposed a kinetic hydration model to determine the hydrating layer thickness of slag particles. [PERSON] et al. [15] developed a kinetic hydration model for slag geopolymer and found that the slag reaction consists of a process of phase boundary reaction and a process of diffusion. [PERSON] et al. [16] constructed a thermodynamic model of cement-slag blends and evaluated the hydration product assemblage. [PERSON] et al. [17] analyzed the hydration products of cement-slag-fly ash-limestone quaternary blends and found the optimal combination for strength. [PERSON] et al. [18] analyzed the hydration kinetics of cement-slag composite considering the influence of the slag replacement percentage and curing temperature. [PERSON] et al. [19] analyzed the reaction extent of cement, slag, and total binder in binary blends based on the experimental study results of hydration heat, combined water, and backscattered electron image analysis. Based on our investigations, we found that previous models in this field have several weak points. First, the models of [PERSON] et al. [11], [PERSON] et al. [12], and [PERSON] et al. [13] are statistical models that are difficult to generalize to different mixing proportions and various curing conditions. Second, the models of [PERSON] et al. [14] and [PERSON] et al. [15] are used for alkali-activated slag concrete. It is difficult to simulate the hydration of cement-slag binary composite concrete in these models. Third, the models of [PERSON] et al. [16] and [PERSON] et al. [17] are useful for evaluating the phase assemblages of hydration products, however, the reaction degrees of slag in the works of [PERSON] et al. [16] and [PERSON] et al. [17] were derived from experimental measurements, which require a large amount of time and money. In other words, if a kinetic model could be used to calculate the reaction extent of slag in binary blends of cement-slag, the use of time- and cost-consuming experimental measurements can be eliminated. Fourth, the studies of [PERSON] et al.