scholarly journals Assessing the Influence of Moisture Damage under Repeated Load on Multilayer Interface Bond Strength of Asphalt Concrete

2020 ◽  
Vol 26 (11) ◽  
pp. 21-42
Author(s):  
Samah Abdul razzaq Alnuami ◽  
Saad Issa Sarsam
Keyword(s):  
Bond Strength ◽  
Asphalt Concrete ◽  
Permanent Deformation ◽  
Moisture Damage ◽  
Application Rates ◽  
Tack Coat ◽  
Interface Bond Strength ◽  
Repeated Load ◽  
Moisture Conditions ◽  
Interface Bond

The performance and durability of the asphalt pavement structure mainly depend on the strength of the bonding between the layers. Such a bond is achieved through the use of an adhesive material (tack coat) to bond the asphalt layers. The main objective of this study is to evaluate the effect of moisture in conjunction with repeated traffic loads on the strength of the bonding between asphalt layers using two types of tack coats with different application rates. Using the nominal maximum size of aggregate (NMAS), the layers were graded (25/19) and (19/9.5) mm. The slabs of multilayer asphalt concrete were prepared using a roller compactor using two types of tack coats to bond between layers, namely rapid curing cut back asphalt (RC-70) and cationic medium setting emulsion (CMS), with different application rates.  Six extruded cores with a diameter of 116 mm each form the prepared slab has been obtained. Core specimens were subjected to moisture damage according to the American Association of State Highway and Transportation Officials (AASHTO), after which repeated bond shear stresses and monotonic tests are practiced. It is concluded that permanent deformation increased with moisture-induction under repeated load for both interfaces and tack coat types. The (CMS) as a tack coat had less permanent deformation values than RC-70 for both interface types and all application rates. In contrast, the interface bond strength (IBS) value was higher than that for (RC-70) in both interface types after moisture conditions. The trend of the results illustrates that (IBS) decreased with moisture conditions under repeated load, as compared to samples under repeated load only.

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

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.

scholarly journals Influence of Ageing on Flexible Pavement Interface Bond under Repeated Shear Stresses

2020 ◽  
Vol 2 (2) ◽  
pp. 462-475
Author(s):  
Saad Issa Sarsam ◽  
Samah Abdulrazzaq AL Nuaimi
Keyword(s):  
Shear Strength ◽  
Permanent Deformation ◽  
Research Work ◽  
Application Rate ◽  
Shear Stresses ◽  
Interface Shear ◽  
Concrete Core ◽  
Application Rates ◽  
Tack Coat ◽  
Interface Bond

The durability of interface bond was not sufficiently taken into consideration, and the research work in this field is scares and scattered. The interface bond usually practices dynamic shear stresses throughout its service life while ageing due to volatilization provide stiffness at the interface. In this investigation, an attempt has been made to assess the durability of the interface bond in terms of resistance to ageing under repeated shear stresses. Two types of tack coat (Rapid Curing cutback RC-70 and Cationic Medium setting emulsion CMS) and three application rates have been implemented in the preparation of two layers slab samples (base overlaid by binder, and binder overlaid by wearing) courses using roller compactor. Asphalt concrete core specimens were obtained from the roller compacted slab samples and subjected to long term ageing, then the specimens were subjected to 1200 repeated shear stress cycles. The accumulation of permanent deformation was monitored. Afterwards, the specimens were tested for interface shear strength at 20 °C. Control specimens were also tested for comparison. It was concluded that ageing reduces the total microstrain for RC-70 tack coat by (43.6, 25.6, and 29.5) % and (50, 51.3, and 30.2) % for (binder-base) and (wearing-binder) interfaces for the application rate of (0.15, 0.33, 0.5) l/m2  respectively. However, ageing reduces the total microstrain for CMS tack coat by (37, 35.5, and 40.3) % and (45.2 , 49, and 46.8) % for (binder-base) and (wearing-binder) interfaces for the application rate of (0.1, 0.23, 0.35) l/m2  respectively. Ageing increases the interface bond shear strength by a range of (8-27)% for various interfaces, tack coat type and application rates.

Effects of Tack Coat Application on Interface Bond Strength and Short-Term Pavement Performance

2017 ◽  
Vol 2633 (1) ◽  
pp. 1-8 ◽  
Author(s):  
Ramendra Das ◽  
Louay N. Mohammad ◽  
Mostafa Elseifi ◽  
Wei Cao ◽  
Samuel B. Cooper
Keyword(s):  
Shear Strength ◽  
Bond Strength ◽  
Pavement Performance ◽  
Interface Bonding ◽  
Short Term ◽  
Surface Type ◽  
Tack Coat ◽  
Interface Bond Strength ◽  
Interface Bond ◽  
Coat Material

The objectives of this study were to evaluate the effects of pavement surface type, tack coat material, and application rate on the interface bond strength between a hot-mix asphalt overlay and underlying pavement layers in the field. The effects of interface bonding on short-term pavement performance were also investigated. Three field projects that included 14 in-service test sections were constructed with four types of emulsified tack coats applied at different residual application rates. Specimens were cored from the test sections, and the interface shear strength (ISS) was measured at different service times with a direct shear test device, the Louisiana interlayer shear strength tester. The results of the study showed that, with respect to surface type, the ISS was largely dependent on the type of pavement surface receiving tack coat materials and surface texture. With respect to tack coat material type, the use of a nontracking (rapidly setting) tack coat resulted in a greater ISS than the use of slowly setting (SS-1 and SS-1H) tack coats, a result that was primarily attributed to the stiffer base asphalt cement used in the nontracking tack coat material. With respect to the effects of service time, the interface bonding strength increased with service time in all field projects and for all surface types. This phenomenon was primarily attributed to tack coat curing, which was more pronounced with slowly setting tack coat materials. Laboratory ISS test results correlated well with short-term field performance. All test sections except those that did not meet the minimum ISS threshold of 40 psi, recommended by NCHRP Project 9-40, exhibited satisfactory cracking performance.

Assessing the Moisture Susceptibility at Interface of Asphalt Concrete Pavement Layers

2020 ◽  
Vol 1 (1) ◽  
Author(s):  
Saad Issa Sarsam ◽  
Samah Abdulrazzaq AL Nuaimi
Keyword(s):  
Shear Strength ◽  
Asphalt Concrete ◽  
Moisture Damage ◽  
Shear Stresses ◽  
Horizontal Deformation ◽  
Moisture Susceptibility ◽  
Cyclic Shear ◽  
Bond Shear Strength ◽  
Application Rates ◽  
Tack Coat

The asphalt concrete flexible pavement consists of many layers interconnected by tack coat binder. The resistance of the bonding tack coat to the impact of moisture that ingress through the cracks into the interface of asphalt concrete can cause premature matrix degradation of pavement structure. In this investigation, the influence of moisture susceptibility on the bond strength and horizontal deformation of three layers of asphalt concrete are assessed under repeated shear stresses. The suitability of two types of tack coat (Rapid curing cutback RC-70 and medium setting cationic emulsion CMS) to support the resistance to moisture damage have been investigated. Asphalt concrete slab specimens have been prepared with the aid of roller compactor for the typical three layers usually implemented in flexible pavement in Iraq (wearing, binder and asphalt stabilized base courses) with (12, 19.5 and 25) mm nominal maximum size of aggregate. Layers were bonded by tack coat after construction of the bottom layers. Core specimens have been obtained and subjected to moisture damage then practiced 1200 cyclic shear stresses in the Pneumatic Repeated Load System PRLS using a special manufactured mold. Control core specimens have been obtained and practiced 1200 cyclic shear stresses. Specimens were tested for bond shear strength. The bond shear strength and horizontal deformation under repeated shear stresses were analyzed and compared. It was concluded that the horizontal permanent deformation increases by a range of (4 -27) % and (2-57) % after moisture damage when RC-70 and CMS tack coat were implemented respectively at various application rates. However, the reduction in bond shear strength due to moisture damage ranges between (2-17) % and (5 -30) % for RC-70 and CMS Tack coat interfaces. CMS tack coat exhibits higher bond shear strength ratio BSSR than RC-70 tack coat for all the application rates and is recommended for use from the moisture susceptibility point of view. Keywords: Moisture Susceptibility; Interface; Asphalt Concrete; Bond Shear; Horizontal Deformation; Tack Coat;

scholarly journals Assessing the Effect of Nano Hydrophobic Silane Silica on Aggregate-Bitumen Interface Bond Strength in the Spring-Thaw Season

2019 ◽  
Vol 9 (12) ◽  
pp. 2393 ◽  
Author(s):  
Wei Guo ◽  
Xuedong Guo ◽  
Jilu Li ◽  
Yingsong Li ◽  
Mingzhi Sun ◽  
...  
Keyword(s):  
Shear Strength ◽  
Bond Strength ◽  
Moisture Damage ◽  
Interface Shear Strength ◽  
Interface Shear ◽  
Modified Asphalt ◽  
Bonding Failure ◽  
Interface Bond Strength ◽  
Hydrophobic Silane ◽  
Interface Bond

In the asphalt–aggregate system, the aggregate-bitumen interface cohesive and adhesive bond determine the mechanical properties of asphalt pavement. The presence of moisture leading to adhesive failure at the binder-aggregate interface and/or cohesive failure within the binder or binder-filler mastic is the main mechanisms of moisture damage in the spring-thaw season. In order to evaluate the effect of nano hydrophobic silane silica (NHSS) on aggregate-bitumen interface bond strength in the spring-thaw season, an aggregate-bitumen interface bond strength test was proposed to quantify the interface bond strength of base asphalt and NHSS modified asphalt. Then, the effect of temperature, freeze-thawing cycles and moisture on aggregate-bitumen interface shear strength of base asphalt and NHSS modified asphalt was also discussed. The results illustrated that the shear failure dominated the aggregate-bitumen interface bonding failure in the spring-thaw season, and temperature and moisture had a significant effect on interface shear strength of modified and unmodified asphalt. Moreover, the addition of NHSS could increase the aggregate-bitumen interface shear strength under any working conditions. Furthermore, the moisture damage model of aggregate-bitumen interface shear strength of base asphalt (BA) and NHSS modified asphalt was established based on a research method combining numerical calculations and laboratory tests.

Compilation of Pavement Interface Bond Strength Devices for Bond Strength Quantification

2014 ◽  
Vol 71 (3) ◽  
Author(s):  
Chang Fung-Lung ◽  
Haryati Yaacob ◽  
Mohd. Rosli Hainin ◽  
Ahmad Safuan A. Rashid
Keyword(s):  
Bond Strength ◽  
Test Performance ◽  
Flexible Pavement ◽  
Multilayered Structure ◽  
Current State ◽  
Tack Coat ◽  
Interface Bond Strength ◽  
Overall Performance ◽  
Torsional Mechanism ◽  
Interface Bond

Flexible pavement is a multilayered structure constructed in layers. In order to ensure proper bonding such that a pavement behaved monolithically, tack coat is often applied. The developed pavement interface bond strength is therefore paramount in governing the overall performance of pavement serviceability. The present work reviews the current state of pavement interface bond strength quantification mechanisms, and the devices developed based on the mechanism. Related accessible literatures are collected and analyzed to compile the characteristics of each bond testing devices and evaluated for the capabilities and test performance. The investigation reveals 3 testing mechanisms incorporating shearing (pushing), tensile (pulling) and torsioning (twisting). However, shearing test seems to be the most popular device adopted to investigate the bond strength between two interfaces in contact, utterly due to the simplicity of the test setup. For tensile mechanism, the developed devices are generally portable and are mostly used to examine the tack coat quality. Finally, the device with torsional mechanism is not so popular as compared to the aforementioned mechanism. Nonetheless, it is developing steadily with the continuous research.

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