Use of hydrated lime and cement bypass dust as alternative fillers in hot mix asphalt

Abstract

Road quality has an important role for the smooth traffic flow. Asphalt concrete layers are the most significant elements of roads; but due to their position, they are exposed to the influence of many external factors (water, sun, freeze, fuel) which affect their lifespan. At the same time, limited quantities of new materials are forcing investors to use available alternative materials that fulfill quality requirements and possibly reduce costs. Since filler is the second most expensive ingredient of asphalt mixtures, it becomes necessary to improve its properties by introducing certain additives or alternative fillers that may be used instead of mineral filler. This study examines the use of hydrated lime and cement bypass dust (CBD) as partial and full replacements of limestone filler. Within this study, one mixture contained hydrated lime as a partial replacement of limestone filler and two mixtures contained CBD as a partial and full replacement of limestone filler in asphalt mixture AC 11s SURF B50/70. The properties of these three mixtures were compared with a control mixture (CM) that contained limestone mineral filler. All mixtures were tested to determine their: volumetric properties, freeze-thaw resistance, water sensitivity, rutting resistance and stiffness. Results indicate that the substitution of CBD with limestone decreases optimal binder content and improves rutting resistance, while hydrated lime substitution significantly improves freeze-thaw resistance.