The Effect of Various Paving Time on the Time Available for Compaction of Warm Mix Asphalt (WMA)

Abstract

Warm Mix Asphalt (WMA) is a technology that allows significant lowering of the production and paving temperature of conventional Hot Mix Asphalt (HMA). By reducing the viscosity of bitumen and/or increasing the workability of mixture, some WMA technologies can reduce the temperature to even lower without compromising the performance of asphalt. High demand for new asphalt pavements often requires that paving is to be done in an unfavorable condition such as low air temperatures, high wind speeds, and night construction that will influence the cooling rate of asphalt pavements, affecting the Time Available for Compaction (TAC). TAC is a period taken by the asphalt mix to cool and stiff to the point where it can absorb the applied compaction energy without allowing the aggregate particles to move and avoid higher cooling rate which 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 that can be used to predict these control elements and to be specifically related to the local conditions. This study was conducted with the aim to determine the appropriate TAC of WMA when paved at different time (day and night) through laboratory tests. It focused on WMA AC 14 of mix type for wearing course and AC 28 of mix type for binder course. The results indicated that the cooling rate of WMA is significantly affected by the amount of solar flux (on daytime), ambient and base temperature thus influencing the Time Available for Compaction (TAC). The TAC tends to increase during daytime at 1pm as compared to 9am, 5pm and during night time.