Investigation of cracking resistance of cold asphalt mixture designed for ultra-thin asphalt layer

Ultra-thin asphalt layers are mostly constructed at high producing temperatures of 165-180 celcius, which results in high energy consumption and extra aging of asphalt binders. Those influences could be eliminated by employing the cold-mix process. However, the reduced cracking resistance of cold asphalt mixtures should be addressed. The objective of this study is to design a preferable cold mix asphalt mixture which can be used for ultra-thin asphalt layer. A cold mix ultra-thin asphalt layer (GT-10 C) with comparable anti-cracking performance was developed through the use of high-performance binder, basalt fibers, and specially designed aggregate gradation. Several cracking resistance tests were employed including the low-temperature bending test, impact toughness test, and semi-circular bending test. In addition, a specified test method was developed for determining cracking resistance and durability of the ultra-thin asphalt layers by using compounded slabs. The testing results were compared with the performance of a conventional hot mix ultra-thin asphalt layer (Hot-UA) and a common micro-surfacing layer with cold mix (Cold-UA). It was found that GT-10 C had larger ultimate tensile strain, impact and fracture toughness than Hot-UA and Cold-UA, and a better fracture life in the thin layer cracking resistance test as well. This research provides a potential technology for producing cold mix ultra-thin asphalt layers.