Application of intermediate temperature semi-circular bending test results to design mixtures with improved load-associated cracking resistance

This paper describes the development and practical application of regression equations to estimate the relative load-associated cracking resistance of asphalt mixtures from properties that are included in specifications and controlled through current quality control and acceptance procedures. This work was part of a research study performed through the Wisconsin Highway Research Program to evaluate changes to the composition of asphalt concrete mixtures that should be considered to improve the durability of flexible pavements. Based on the findings of a synthesis of current research, a laboratory experiment was conducted to quantify the effect of (1) effective binder volume, (2) virgin binder low temperature performance grade, (3) recycled binder content, and (4) polymer modification on the resistance of typical Wisconsin mixtures to ageing and load-associated cracking. For the types of mixtures normally used in Wisconsin, the laboratory experiment found mixture composition had little effect on ageing; however, load-associated cracking resistance was significantly affected. The laboratory experiment produced a regression equation that was used to recommend revised volumetric criteria that provide equivalent load-associated cracking resistance and allow producers the flexibility to design mixtures using a range of effective binder contents, recycled binder contents, and virgin binders.