Document Type

Thesis - Open Access

Award Date


Degree Name

Master of Science (MS)

Department / School

Civil and Environmental Engineering

First Advisor

Rouzbeh Ghabchi


Interlayer Shear Strength, Louisiana Interlayer Shear Strength Tester, Pavement Bond Strength, Tack Coat


Tack coat is an asphaltic material applied between asphalt pavement layers. Since pavement is a multilayered structure, it is highly important to make proper bond between the layers to achieve a monolithic behavior. Hence, inadequate bond due to application of inadequate amount of tack coat may lead to poor structural behavior and premature failure. Also, applying excessive amount of tack coat may lead to layer slippage and binder migration. Therefore, it is highly important to apply an optimum amount of tack coat between layers. Over the past decades several studies have been conducted to determine the optimum tack coat application rate, based on tack coat type, surface preparation, and temperature. In those studies, different types of tests were used to determine the Interlayer Shear Strength (ISS). It was reported that, many factors affect the ISS such as tack coat application rate, tack coat type, layer type and texture, cleanliness, test temperature, and confinement pressure among other factors. In the current study, a Louisiana Interlayer Shear Strength Tester (LISST) device was used to measure the ISS values of layered samples. The test matrix included 2 main parts, one to identify the optimum tack coat application rate and the other part to study the effect of moisture conditioning on ISS of the samples prepared at optimum application rate. The top layer of all of the test samples were prepared in a way to simulate a new Hot Mix Asphalt (HMA) overlay. The top HMA layer was compacted on four types of bottom layers, namely new HMA, aged and worn HMA, milled HMA, and grooved Portland Cement Concrete (PCC). Three types of tack coats were evaluated: CRS-2P, CSS-1h, and SS-h. Tack coats were applied at four rates: 0, 0.140, 0.281, and 0.702 liters per square meter (L/m2). Results indicated that for the tack coat types evaluated in the current study CSS- 1h exhibited the highest ISS values on all the surface types compared to those measured for surfaces without any tack coat. Also, on all HMA bottom layer types, CSS-1h showed the best performance at lowest application rate. It was observed that, CSS-1h was the only tack coat which showed higher ISS compared to no tack coat application. On PCC bottom layers, application of the SS-h tack coat resulted in a higher ISS value compared to other tack coats. The highest ISS value measured for the interface of PCC and HMA was observed when the SS-h tack coat was used. Generally, the CRS-2P tack coat was found to be more effective in improving the ISS at higher application rates while CSS-1h was effective when it was applied at a lower application rate. The highest ISS value was observed when tack coat was applied on aged and worn HMA bottom layers followed by new HMA, milled HMA, and grooved PCC. For both new HMA and aged and worn HMA bottom layers, CSS-1h tack coat applied at a rate of 0.140 L/m2 showed the best performance. For milled HMA bottom layers CSS-1h and SS-h tack coats applied at a rate of 0.140 L/m2 exhibited a higher effectiveness in improving the ISS value. For grooved PCC bottom layers all the tested tack coats exhibited increased ISS values than samples prepared without applying any tack coat. Hence, it is highly important to use any tack coat for an overlay of PCC bottom layer. Moisture conditioning was found to negatively affect the ISS of the samples with PCC bottom layer regardless of the tack coat type. However, the ISS values of the samples containing tack coats applied at their optimum application rates on other types of HMA bottom layer were not found to be negatively affected due to moisture conditioning.

Library of Congress Subject Headings

Pavements -- Overlays.
Pavements, Asphalt -- Materials.
Pavements, Asphalt concrete.
Asphalt emulsion mixtures.
Shear (Mechanics) -- Testing.


Includes bibliographical references



Number of Pages



South Dakota State University



Rights Statement

In Copyright