Effect of weather aging on volume expansion properties of steel slag

Steel slag, one of the huge industrial waste sources, which has many outstanding advantages (hardness, roughness, angularity, and abrasion resistance) has been used as an aggregate in asphalt concrete to bring many benefits. However, steel slag is rarely used in Portland cement concrete because of concerns that it may give rise to volume expansion. One of the main causes of this problem is that the steel slag contains a considerable amount of free lime. This free lime content can be reduced if it is hydrated or the steel slag is aged by water. Therefore, in this study, the effects of weather aging on volume expansion properties of steel slag will be considered. The pH, free lime and volume expansion tests were carried out on weather-aged steel slag samples (after aged by 1 month, 6 months, 12 months and 30 months) and compared with non-aged one. The results showed that the 6 month-aged, 12 month-aged, and 30 month-aged steel slag samples had low free content, low pH and volume expansion. Moreover, steel slag aged more than 6 months has very low volume expansion, meeting the requirements of ASTM D492 for use as aggregate in concrete.