Influence of Asphalt Tack Coat Materials on Interface Shear Strength

Abstract

Asphalt tack coat is a light application of asphalt, usually asphalt diluted with water. It is used to ensure a bond between the surface being paved and the overlying course. Normally, hot asphalt cements, emulsified asphalts, or cutback asphalts are used as tack coats. The objective of this study was to evaluate the practice of using tack coats through controlled laboratory simple shear tests and determine the optimum application rate. The influence of tack coat types, application rates, and test temperatures on the interface shear strength was examined. Four emulsions (CRS 2P, SS-1, CSS-1, and SS-1h) and two asphalt binders (PG 64-22 and PG 76-22M) were selected as tack coat materials. The residual application rates considered were 0.00 (0.00), 0.09 (0.02), 0.23 (0.05), 0.45 (0.1), and 0.9 (0.2) L/m 2 (gal/yd 2 ). A simple shear test was performed to determine the shear strength at the interface at two test temperatures, 25°C (77°F) and 55°C (131°F). The results indicated that CRS-2P emulsion was the best tack coat type and 0.09 L/m 2 (0.02 gal/yd 2 ) was the optimum application rate at which a maximum interface shear strength was measured for both test temperatures.

Development of a framework for standardisation of interlayer bond of asphalt pavements

“…Although during recent years the bonding characteristics between asphalt pavement layers have been discussed in a remarkable number of conference and journal papers, master or PhD theses and other publications (e.g. Ziari and Khabiri, 2007, 162 Tschegg et al, 2007, Leng et al, 2008, Mohammad et al, 2009), large scale data collection in this field has not been within high priority research focus, so far. This is partly due to the fact that, as mentioned in Chapter 2, the bond between asphalt pavement layers has not been part of the standardisation and normalisation for a long period of time.…”

Evaluation of Asphalt Pavement Layer Bonding Stress

“…If adjacent layers do not bond to each other, they essentially behave as multiple independent thin layers which result in a significant reduction in the shear strength of the pavement composite structure, thus, making it more susceptible to a variety of distresses such as cracking, rutting, and potholes (West et al 2005;Hachiya, Sato 1997;NAPA 2000). In the recent years, interface shear performance has been widely investigated, especially given that the behavior of in-service pavements has on occasion revealed several types of premature distresses, due to an inadequate selection of interface boundary conditions during the pavement design stage Collop et al 2009;Romanoschi, Metcalf 2001;Romanoschi 1999;Canestrari et al 2005;Mohammad et al 2005;Miro-Recasens et al 2005;Partl et al 2006;Diakhaté et al 2006;Chaignon, Roffe 2001;Al-Hakim et al 2000;Ascher, Wellner 2007). The photograph of typical slippage failure of the pavement composite layer occurring at locations where traffic accelerates, decelerates, or turns is the most commonly observed problem as shown in Figure 1.…”

“…Mrawira and Damude reported that non-tacked overlays exhibited slightly higher maximum shear strengths than tack coated overlays at the shear testing of an emulsion grade SS-1 tack coat between freshly paved asphalt layers by a constant rate of 1 mm/min at 22 °C (Mrawira, Damude 1999). Mohammad et al investigated on the influence of the different emulsions and two asphalt binders as asphalt tack coat materials, and five different tack coat application rates ranging from 0.0 l/m 2 to 0.9 l/m 2 at test temperatures of 25 °C and 55 °C on the shear strength of interfaces between asphalt pavement composite layers (Sivilevičius 2011;Vaitkus et al 2011;Mohammad et al 2002). The Superior Performing Asphalt Pavement (Superpave) shear tester was used for applying a shearing load at a constant rate of 218.27 N/min; and the results indicated that the CRS-2P emulsion was the best tack coat type; and 0.09 l/m 2 , was the optimum application rate at which the maximum interface shear strength was measured for both test temperatures.…”

Fatigue Investigation of the Interface Shear Performance in Asphalt Pavement

“…Several testing devices have been developed worldwide with different working schemes. They are able to test cylindrical or prismatic specimens with different sizes (Sangiorgi et al, 2002;Raab & Partl, 2004;Ferrotti et al, 2012) and have been used to evaluate and compare the influence on the interface shear strength of several factors such as the tack coat efficiency (Mohammad et al, 2002), the surface conditions (Mohammad, 2012) or the surface profile . and setting simplicity.…”