An investigation into the effects of tack coat application rate on interlayer shear bond strength

Asphalt emulsion is the most widely used tack coat material in the U.S. The objective of this study is to investigate factors that may affect the interlayer bond shear strength of asphalt emulsion tack coats of both laboratory and field compacted samples. The laboratory study included six types of tack coat materials applied on two surfaces with two residual application rates. The field study phase involved validation of the interlayer shear performance findings using field cores extracted from paving projects. The field study included taking cores of the existing layer, emulsions used for interlayer bonding, and loose mixes of new asphalt layers. Materials were collected to produce the laboratory prepared specimens for comparison with the field cores. Results of the laboratory study demonstrate that there is a direct relationship between the roughness (texture) of the existing surface and the interlayer shear strength (ISS) between two surfaces. Statistical analysis provided a strong correlation and indicated that 79% of the data variance can be explained with surface texture, emulsion type, application rate, and replicate effects. Comparing field cores with laboratory produced samples showed no clear relationship between the shear strength of laboratory and field specimens. It is speculated that the difference in compaction of the upper layers in the laboratory and field, and effect of shearing during coring of the samples from the field, resulted in higher laboratory shear values relative to field core values. The study highlights major challenges in using laboratory prepared samples to predict field behavior of tack coats.

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Assessment on Bonding Potentials of Trackless Tack under a Thin Overlay

Infrastructures ◽

10.3390/infrastructures6090126 ◽

2021 ◽

Vol 6 (9) ◽

pp. 126

Author(s):

Ah Young Seo ◽

Maryam S. Sakhaeifar ◽

Bryan T. Wilson

Keyword(s):

Statistical Analysis ◽

Bond Strength ◽

Shear Bond Strength ◽

Critical Role ◽

Shear Resistance ◽

Marginal Effect ◽

Bond Performance ◽

Several Variables ◽

Interlayer Shear ◽

Bonding Characteristics

Trackless tacks are used to minimize the loss of tack materials caused by adherence to moving tires. During the last two decades, the paving industry and highway agencies have had an increasing interest in the use of trackless tacks to ensure an adequate bond between the overlay and the existing pavement. Therefore, the need for more studies on the bonding characteristics of various trackless tacks is growing. The purpose of this study is to measure the bonding potential of trackless tacks and identify several variables that affect the shear resistance in terms of bonding strength and energy using statistical analysis. The improvement of interlayer shear resistance by tack treatment is different depending on the tack and surface types. Higher tack reactivation temperatures increase the interlayer shear resistance. Compaction effort is considered to have only a marginal effect on bond performance. Tack and surface types play a more critical role in determining the shear bond strength than residual tack rate in the field experiment.

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Effect of tack coat emulsion type, application rate, and surface type and texture on early-age interlayer shear strength of pavements in cold regions

International Journal of Pavement Engineering ◽

10.1080/10298436.2020.1828587 ◽

2020 ◽

pp. 1-16

Author(s):

Rouzbeh Ghabchi ◽

Chamika Prashan Dharmarathna

Keyword(s):

Shear Strength ◽

Application Rate ◽

Early Age ◽

Surface Type ◽

Cold Regions ◽

Interlayer Shear ◽

Tack Coat ◽

Interlayer Shear Strength

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Influence of Surface Texture on Interface Bond Shear Strength of Asphalt Concrete

Civil Engineering Beyond Limits ◽

10.36937/cebel.2020.003.002 ◽

2020 ◽

Vol 1 (3) ◽

pp. 8-14

Author(s):

Saad Issa Sarsam

Keyword(s):

Shear Strength ◽

Bond Strength ◽

Surface Texture ◽

Asphalt Concrete ◽

Maximum Size ◽

Application Rate ◽

Application Rates ◽

Tack Coat ◽

Base Course ◽

Interface Bond

The bonding strength provided by the tack coat between asphalt concrete layers at the interface is considered as an essential issue in the performance of the flexible pavement throughout its service life. However, the surface texture of the pavement surface exhibits another essential issue in the bond strength. In this investigation, three layers of asphalt concrete (base, binder and wearing) courses with (25, 19, and 12.5) mm of nominal maximum size of aggregates have been prepared using roller compactor. Rapid curing cutback RC-70 and cationic medium setting emulsion CMS have been implemented as tack coats with three application rates. The slab specimens were subjected to mean texture depth determination using sand patch method. Core specimens of 102 mm diameter were obtained from the prepared slab samples and subjected to interface bond strength test with the aid of a special manufactured mold. Test results were analyzed and compared. It was concluded that when RC-70 tack coat was implemented, asphalt concrete binder course laid on base course exhibited the highest shear strength of 1600 kPa at an application rate of 0.33 liter/m2 when compared to other application rates. Asphalt concrete wearing course laid on binder course exhibited the highest shear strength of 1515 kPa at an application rate of 0.15 liter/m2 when compared to other application rates. When CMS tack coat was implemented, asphalt concrete binder course laid on base course exhibited the highest shear strength of 1620 kPa at an application rate of 0.23 liter/m2 when compared to other application rates. Finally, the asphalt concrete wearing course laid on binder course exhibited the highest shear strength of 2272 kPa at an application rate of 0.23 liter/m2 when compared to other application rates.

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