New Thin Overlay Method with Heating and Scratching of Cracked Existing Asphalt Pavement

In Japan, the demand for repairing existing pavements is growing as the increase of the road stock. Besides, cheaper, more durable and environment-friendly construction methods for repairing asphalt pavements have been required because of shortage of the budget and escalation of the interest in environment. Thin overlay method is one of repairing methods to meet the needs mentioned above. However, it is too difficult to control temperature of the thin overlay and to compact the thin overlay enough to combine with existing asphalt pavement. So, a new method of thin overlay with heating and scratching of cracked existing pavement just before overlay (HS overlay) was developed, in order to prevent a decrease of pavement temperature and to ensure bonding in boundary of asphalt layers. A road heater for surface recycling of asphalt pavements is used to heat and scratch existing pavement. It is thought that cost using a road heater is not so expensive, that the total construction cost for HS overlay doesn't increase significantly. Shearing test, bending test and wheel tracking fatigue test were conducted to determine characteristics of HS overlay in the laboratory. From those results, the durability of HS overlay is ensured to be superior to an ordinary thin overlay without heating and scratching the existing pavement. Based on such results of laboratory tests, a test section was constructed to evaluate performance of cracked asphalt pavement repaired with HS overlay in site. The pavement surface condition observed there during 5 years proved the good resistance to cracking and rutting of HS overlay.