Evaluating time available for compaction of HMA

Abstract

Road sector development has rapidly increased in Sri Lanka after the civil war. Asphalt concrete is widely used for the construction of roads due to speedy construction, durability, riding quality and easy to apply compared to other materials. The primary objective of this research is to find the time available for compaction of hot mixed asphalt concrete with effect of wind velocity, lay down temperature, and ambient temperature. The secondary objective is to check the value 1350C as the minimum lay down temperature for tropical climates. In this study, cooling time was measured in laboratory and field with different asphalt layer thickness, base temperature, and ambient temperature with different mixtures and lay down temperatures. According to standard specification for construction and maintenance of roads and bridges, it has specified that the breakdown and the intermediate rolling shall be carried out at temperature not less than 1350C and 1150Crespectively. The final rolling shall be completed before the temperature of the mix falls below 90 0C. According to the field data, cooling rate at 12.30 pm to 1.30pm was low during day time and that time was more suitable for asphalt laying and also found that HMA lay down temperature below 1350C was not significantly affected to compaction of HMA because compaction density can be achieved applying more roller passes and compaction effort. But in laboratory test, stability of HMA below 1150C was contradict to the specification. So that the value of 1350C not for minimum lay down temperature of HMA and recommended to complete all the compaction process before reaching 1150C and final rolling complete before 900C during day time in western province.