Abstract:
In Thailand, general approach to the design of asphalt pavement is to emphasize on high weight bearing capacity employing dense aggregate grading. However, as Thailand{174}s climate is influenced by monsoon, heavy rainfall is experienced most of the year, and as this method of design gives an impermeable pavement surface most of the time after a heavy rain, there is an excess rainwater left over the pavement surface due to insufficient time for it to drain-off sideways. This resulted in lowering of skid resistance of the road surface, spraying of water from fast-moving heavy vehicles, and reflection at night. All of which are the factors contributed to road accident. Drainaged asphalt pavement employing gap aggregate grading is considered to be able to improve all these malices exhibited by the afore-mentioned design. The purpose of this research is to study properties of drainaged asphalt concrete in comparison with those using limestone and slag as aggregate. The research also aims at identifying suitability of its application in Thailand. Testings of asphalt concrete in this research is divided into 3 sections: 1) Test of basic properties of drainaged asphalt concrete in comparison with dense grade asphalt concrete ; 2) Comparison of properties of drainaged asphalt concrete using limestone and slag as aggregate; and 3) Identify appropriate thickness of drainaged asphalt concrete to be laid as wearing course on top of the dense grade asphalt concrete. From the results, the drainaged asphalt concrete has a better capability to drain excess water from the pavement surface than that of dense grade asphalt concrete. It also improved the skid resistance between tyres and the surface of the pavement, eliminated spraying and reflection. Mixes employed slag gave higher bearing capacity than that using limestone. When compared the working performance of the pavement to the cost of the binder, It was found that the most suitable binder is the mixture containing asphalt cement and 12% polymer (40% Styrene Butadiene Styrene, SBS, in resin) by weigh which is an equivalent of 4.8% SBS by weight.