MOISTURE SENSITIVITY OF ASPHALT MIXTURES CONTAINING E.A.F STEEL SLAG

Moisture damage, sometimes called stripping, is the progressive deterioration of asphalt mixtures due to loss of adhesion between the asphalt binder and the aggregate surface and/or loss of cohesion within the binder due to the inltration of water. Stripping usually begins in the bottom of the HMA layer, then, travels upward. A typical situation is a gradual loss of strength over a period of years, which causes rutting and shoving to develop in the wheel path. Many times, stripping is dicult to identify, because surface indicators may take years to show. This type of damage in Hot Mix Asphalt (HMA) is a major cause of pavement failure in tropical regions. There are many possible causes of stripping and inadequate surface drainage or sub-surface drainage is a primary contributor. There are many proposed remedial actions to alleviate the stripping phenomena of asphalt mixtures, such as using anti-stripping agents, lime slurry with compatible aggregates and modied binders. This study aims to investigate the feasibility of using E.A.F steel slag aggregate in HMA mixtures to reduce their stripping phenomena. Steel slag is a byproduct that makes 15 to 20% of the iron-processing product in an integrated steel mill. Every year, signicant quantities of steel slag are produced as a by-product of steel industries in Iran. Although it can be used as an articial source of aggregates in the pavement industry, it is disposed for landlls. In this research, the chemical and physical properties of the steel slag were evaluated rst. Then, 50% and 100% of the limestone, as ne, coarse and total aggregate in the asphalt mixture was replaced by EAF, and the moisture sensitivity of the mixes was evaluated. The results showed that the use of steel slag as the coarse portion of the aggregates will enhance Marshall stability, resilient modulus, tensile strength and resistance to the moisture damage of HMA mixtures.