Temperature Dependence of Immersion Expansion Ratio of Steel Slag for Road Construction

Steel slag, a by-product of the steelmaking process, contains free-lime which can expand upon hydration. This expansion characteristic necessitates pre-aging when used as a subbase material. Various countries regulate the expansion characteristics of steel slag through different test methods and standards. However, the temperature conditions of these tests and their correlation to actual environments are not clearly defined. This study aimed to evaluate the temperature dependence of the immersion expansion ratio of steel slag for road construction through expansion tests. The results identified the rate-limiting step in the hydration process and calculated the reaction rate constant. The study compared the immersion expansion test method with actual environments to quantitatively assess the degree of acceleration in the tests. It was found that the hydration of steel slag follows a pseudo-first-order surface reaction. By analyzing the temperature changes in the water tank, the study estimated the continuous immersion expansion test period corresponding to the JIS method. The 80°C continuous immersion expansion test period of 4.1-4.6 days was equivalent to the 10-day JIS immersion expansion test. The JIS immersion expansion standard was found to correspond to a legal service life of 10 years or more.