Abstract:
Pavements serve as the lifeline of modern-day transportation system and play a key role in the development of any country. The service life of pavement mainly depends on two critical factors; quality of materials used in pavement and construction accuracy. One of the key factors during the construction phase is temperature of fresh HMA. Therefore, it is important to study the temperatures in field at which HMA is compacted. This experimental study was conducted to determine the temperature range at which HMA is compacted in field under different set of environmental conditions. Temperatures were measured for 5cm and 8cm layers at the surface, center point, interface point of fresh HMA and air temperature by thermocouple sensors during day and night time. HMA temperature was noted throughout the compaction phase along with total no. of roller passes on test section. Average compaction start temperature for 8 tests was 127.81oC, however, average compaction ending temperature was 62.89oC which is below the 80oC known as cessation temperature for asphalt. HMA compacted below 80oC can affect compaction or in some cases develops distresses due to over compaction. Therefore, it is very important to know the HMA temperature during paving operations so that asphalt could be compacted within optimum temperature range (known as temperature window). Air temperature has critical impact on the temperature loss of HMA. Temperature of 8cm HMA layer reached to the bottom threshold of 80oC 32 minutes earlier when the air temperature dropped from 31.75oC to 19.46oC. Temperature at the center of layer thickness during day tests was on the average 10oC higher than the night tests which can be attributed as the effect of sunlight. Opening time of fresh pavement to traffic was also noted, as the live loads of heavy traffic can cause distresses within relatively hot pavement. Low temperatures at the surface of fresh asphalt during compaction phase misrepresent the higher interior temperatures of asphalt layer. Keywords: HMA Compaction; Environmental Factors; Temperature Differential; Cessation Temperature, Traffic Opening
