Influence of Setting Time of Tack Coat on Bond Strength of Bituminous Paving Layers

Poor adhesion between two successive bituminous layers causes adverse effects on the structural strength of thepavement and develops a numbers of premature failure. to improve the adhesion, it is a general practice to applya tack coat over an existing or newly constructed bituminous surface before laying another bituminous layer. themain objective of this study is to explore the influence of setting time of tack coat material on the bond strength of abituminous layer combination. the influence of tack coat type, application rate and test temperature on the interlayerbond strength (ilbs) have also been studied. two types of bituminous emulsions (crs 1 and cms 2) and two typesof bituminous binders (vg 10 and vg 30) have been selected as tack coat for a typical bituminous layer combination.when no tack coat is used, the influence of time interval between laying of the two successive bituminous layers hasalso been studied. a specially fabricated attachment (named interlayer bond strength testing device) has been used byfitting it to the loading frame of a marshall testing apparatus. it is observed that the ilbs depends on setting time, testtemperature, tack coat type and application rate of a tack coat. out of the four tack coat materials, cms 2 offers themaximum ilbs with minimum quantity requirements in the bituminous layer combination considered. the highestilbs is observed when no tack coat is used, however the upper layer is to be laid and compacted immediately afterthe lower layer.