The environmental effect on the cooling rate of hot mix asphalt pavement

Abstract

High demand for new asphalt pavements often requires that paving be done in an unfavorable condition such as low air temperatures, high speed winds, and night construction that will influence the cooling rate thus affecting the Time Available for Compaction (TAC). Higher cooling rate will reduce the TAC. In local practice, the asphalt paving compaction control mechanisms quoted from the locally used specifications are normally based on the limits of the delivery and laying completion temperatures. There are no items to predict these control elements and to be specifically related to the local conditions. This study was carried out with objective to investigate the environmental effect on cooling rate, aiming to determine the appropriate Time Available for Compaction (TAC) using laboratory tests which include the study parameter; solar flux, base and ambient temperature (daytime and night paving) and wind velocity focusing at HMA ACW 14 of mix type for wearing course and ACB 28 of mix type for binder course. Samples were prepared in slab mold, compacted using manually operated steel roller. Temperature measurements were taken from slabs at middle and surface position. Temperature of mixing was based on JKR specification. A controlled sample was prepared for each mix type, tested in the laboratory without any wind velocity and solar flux effect. Based on the result obtained, it can be concluded that the cooling rate of HMA is significantly affected by the environmental factor thus influencing the TAC. The TAC tend to decrease by 15-50% during windy and night condition while increase up to 100% during daytime condition.