Multidimensional control strategy: a review of optimization methods for the volume stability of steel slag

Steel slag is the main solid waste produced by metallurgical enterprises, which has large output and low effective utilization rate, and has caused serious harm to ecological environment. The poor volume stability of steel slag is the main reason that hinders its large-scale application. How to effectively improve the volume stability of steel slag is the key to its large-scale application. This paper focuses on the volume expansion risk of steel slag and analyzes the research progress of volume stability control of steel slag in multiple dimensions. The analysis results show that: for molten steel slag, both tempering method and process method can significantly reduce the content of active substances in molten steel slag, and achieve the regulation of the volume stability of steel slag. Air quenching can reduce the expansion risk of steel slag by optimizing the particle size of active substances. For cooled solid steel slag: aging treatment is the main means of volume stability treatment of steel slag at present, natural aging treatment period is long and the uniformity is poor, by applying external conditions such as temperature, pressure and humidity, the treatment period can be greatly shortened, but there are also shortcomings such as large wastewater treatment volume, high energy consumption, and the quality of steel slag decline. The carbonization treatment is mainly divided into direct carbonization method and indirect carbonization method. The direct carbonization method improves the carbonization efficiency of steel slag by applying temperature, pressure, CO2 concentration, etc., thus reducing the expansion risk of steel slag. The indirect carbonization method does not rely on traditional carbonization equipment, and induces the precipitation of alkali metal ions in steel slag by adjusting pH value or using microorganisms, thus achieving higher carbonization efficiency. Although the procedure is cumbersome, it does not require strict external conditions; Surface modification can be divided into inorganic modification and organic modification. After modification, the volume expansion risk of steel slag can be significantly reduced. However, acid treatment can produce waste liquid that is difficult to be treated. The combination of various methods for pretreatment of steel slag is better, among which carbonization treatment combined with other methods, whether with acid treatment, alkali activation, or by carbonization to produce artificial steel slag aggregate, further improves the volume stability of steel slag compared with a single treatment. The concrete made of artificial steel slag aggregate shows excellent performance, alleviates the shortage of natural aggregate, and has broad research and application prospects.