COMPARISON OF THE MOISTURE RESISTANCE OF A STEEL-SLAG STONE MASTIC ASPHALT MIXTURE MODIFIED WITH CA(OH)2

Stone mastic asphalt is a type of hot mix asphalt that requires much coarse aggregate, so substitution waste aggregate, such as steel slag, will be an economic reason. The problem is that there are still many things that have not been consistent in various studies related to the moisture resistance of steel slag. The study aimed to compare the effect of Ca(OH)₂ on the moisture resistance of the steel-slag stone mastic asphalt mixture and to determine the optimal Ca(OH)₂ dosage for improving the mixture resistance. This study employs basalt aggregate, steel slag from Krakatau Steel Company, 60/70 penetration asphalt, a stabilizing substance made of bamboo fiber, and Ca(OH)₂. The Texas boiling and the static immersed methods are used to test the adhesion on a loose mixture. The retained Marshall stability and indirect tensile strength are used to test the adhesion on the compacted mix. Testing result of Krakatau steel slag shows that steel slag has a much higher Fe₂O₃ content than steel slag in general and has low water absorption; a poor affinity for asphalt results from this. The result of the Texas boiling method showed a decrease in the percentage adhesion value between steel slag and asphalt compared to natural basalt aggregates and asphalt. Marshall Stability Ratio and Tensile Strength Ratio increased after mixing the asphalt with Ca(OH)₂. Marshall test results show decreased stability in mixtures with steel slag substitution. Adding Ca(OH)₂ increased stability and resistance to moisture significantly. This indicated that Ca(OH)₂ enhances moisture resistance on stone mastic asphalt with modified steel slag.