Evaluation of factors affecting tack coat bond strength

Different types of distress occur in asphalt concrete pavements due to lack of bonding between existing old layer and overlay. Therefore, this paper evaluates the bonding strength between sand asphalt mixture as overlay and roller compacted concrete (RCC) as the existing layer. Four types of tack coat including crumb rubber modified (CRM), grade 60/70 binder, cationic slow-setting (CSS), and cationic rapid-setting (CRS) emulsion were considered, with 200, 400, and 600 g/m(2) dosages. Different RCC surface temperatures including 0, 25, and 60 degrees C were chosen to evaluate the effect of ambient temperature on the bonding strength. Results showed that CRM and 60/70 binders have higher bonding strength in comparison to emulsions. The bonding strength at 0 degrees C for all types of tack coat was significantly lower than other temperatures. The optimum application rates of 200 g/m(2) and 400 g/m(2) were selected for the CSS and CRS emulsified binders respectively. The optimum application rate for the 60/70 and CRM binders was selected as 600 g/m(2).