Laboratory investigation of modified bitumen for interlayer in rigid–flexible composite pavement

2020 ◽  
pp. 089270572093914 ◽  
Author(s):  
Gholamali Shafabakhsh ◽  
Saeed Ahmadi
Keyword(s):  
Shear Strength ◽  
Hydrated Lime ◽  
Crumb Rubber ◽  
Modified Bitumen ◽  
Direct Shear Tests ◽  
Application Rates ◽  
Shear Fatigue ◽  
Tack Coat ◽  
Bonding Properties ◽  
And Performance

Adhesion of composite pavement plays a significant role in the durability and maintenance of this type of pavement. The present research aims to assess the bonding and fatigue performance of rigid–flexible composite pavements through laboratory testing at different tack coat application rates. Three types of modified bitumen, crumb rubber-modified bitumen containing hydrated lime (CR/HL), crumb rubber-modified bitumen containing natural zeolite (CR/NZ), and crumb rubber-modified bitumen (CRMB), were selected as the tack coat. Shear fatigue and direct shear tests were utilized to assess the bonding properties of tack coats. The study also examines the behavior of modified bitumen by examining its viscosity, rheological properties, and performance grade. The results show that CR/NZ exhibits better performance in rheological behavior and at various temperatures compared to CR/HL and CRMB. Also, depending on the type of tack coat, shear strength tests show a range of 0.6–0.9 l m−2 as the optimal tack coat dosage. Finally, based on the optimal tack coat, shear strength ratings for various bitumen types may be classified as CRMB < CR/HL < CR/NZ.

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.

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;

Evaluation of factors affecting tack coat bond strength

2019 ◽  
Vol 46 (4) ◽  
pp. 270-277 ◽  
Author(s):  
Moein Biglari ◽  
Seyed Mohammad Asgharzadeh ◽  
Saleh Sharif Tehrani
Keyword(s):  
Bonding Strength ◽  
Asphalt Mixture ◽  
Crumb Rubber ◽  
Application Rate ◽  
Concrete Pavements ◽  
Factors Affecting ◽  
Roller Compacted Concrete ◽  
Application Rates ◽  
Tack Coat ◽  
Optimum Application

Different types of distress occur in asphalt concrete pavements due to lack of bonding between existing old layer and overlay. Therefore, this paper evaluates the bonding strength between sand asphalt mixture as overlay and roller compacted concrete (RCC) as the existing layer. Four types of tack coat including crumb rubber modified (CRM), grade 60/70 binder, cationic slow-setting (CSS), and cationic rapid-setting (CRS) emulsion were considered, with 200, 400, and 600 g/m2 dosages. Different RCC surface temperatures including 0, 25, and 60 °C were chosen to evaluate the effect of ambient temperature on the bonding strength. Results showed that CRM and 60/70 binders have higher bonding strength in comparison to emulsions. The bonding strength at 0 °C for all types of tack coat was significantly lower than other temperatures. The optimum application rates of 200 g/m2 and 400 g/m2 were selected for the CSS and CRS emulsified binders respectively. The optimum application rate for the 60/70 and CRM binders was selected as 600 g/m2.

scholarly journals Development of an Interface Shear Strength Tester and a Model Predicting the Optimal Application Rate of Tack Coat

2021 ◽  
Vol 1 (1) ◽  
pp. 22-38
Author(s):  
Dowan Kim ◽  
Sungho Mun
Keyword(s):  
Shear Strength ◽  
South Korea ◽  
Predictive Model ◽  
Linear Function ◽  
Polynomial Regression ◽  
Interface Shear Strength ◽  
Interface Shear ◽  
Application Rates ◽  
Non Linear ◽  
Tack Coat

Tack coat application rates and testing conditions differ among nations and construction conditions because various tack coat materials are available. In this study, newer materials are optimized for addition to porous asphalt pavements exposed to torrential rainfall, which is common in South Korea. Interface shear strength (ISS) tests are used to define the optimum application rates (OARs) of tack coat materials generally used in South Korea, by reference to the Korean Design Standard (KDS), the Korean Construction Standard (KCS), and features of pavement construction and bonding. We performed ISS tests using asphalt mixtures with porosities of 3, 5, and 7% to explore the effect of porosity on shear strength. The ISSs associated with varying tack coat proportions were earlier determined by creating polynomial regression equations. Here, we develop a predictive model using a non-linear function to estimate the OAR of tack coat and compare our approach with the earlier polynomial regression analysis. Based on the ISSs, the golden section search method was applied to define the OARs afforded by the predictive polynomial function. We used the generalized reduced gradient algorithm to construct a nonlinear predictive function using data from the ISS tests. Finally, our comparative analysis showed that the predictive model using the non-linear function was superior to the polynomial model in terms of both error rate and predictive tendency.

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 Mechanical Properties and Micro Mechanism of Nano-Clay-Modified Soil Cement Reinforced by Recycled Sand

2021 ◽  
Vol 13 (14) ◽  
pp. 7758
Author(s):  
Biao Qian ◽  
Wenjie Yu ◽  
Beifeng Lv ◽  
Haibo Kang ◽  
Longxin Shu ◽  
...  
Keyword(s):  
Shear Strength ◽  
Void Ratio ◽  
Soil Mass ◽  
Direct Shear ◽  
Test Results ◽  
The Sustainable Development ◽  
Direct Shear Tests ◽  
Soil Cement ◽  
Nano Clay ◽  
New Material

To observe the effect of recycled sand and nano-clay on the improvement of the early strength of soil-cement (7d), 0%, 10%, 15% and 20% recycled sand were added. While maintaining a fixed moisture content of 30%, the ratios of each material are specified in terms of soil mass percentage. The shear strength of CSR (recycled sand blended soil-cement) was investigated by direct shear test and four groups of specimens (CSR-1, CSR-2, CSR-3 and CSR-4) were obtained. In addition, 8% nano-clay was added to four CSR groups to obtain the four groups of CSRN-1, CSRN-2, CSRN-3 and CSRN-4 (soil-cement mixed with recycled sand and nano-clay), which were also subjected to direct shear tests. A detailed analysis of the modification mechanism of soil-cement by recycled sand and nano-clay was carried out in combination with scanning electron microscopy (SEM) and IPP (ImagePro-Plus) software. The test results showed that: (1) CSR-3 has the highest shear strength due to the “concrete-like” effect of the incorporation of recycled sand. With the addition of 8% nano-clay, the overall shear strength of the cement was improved, with CSRN-2 having the best shear strength, thanks to the filling effect of the nano-clay and its high volcanic ash content. (2) When recycled sand and nano-clay were added to soil-cement, the improvement in shear strength was manifested in a more reasonable macroscopic internal structure distribution of soil-cement. (3) SEM test results showed that the shear strength was negatively correlated with the void ratio of its microstructure. The smaller the void ratio, the greater the shear strength. This shows that the use of reclaimed sand can improve the sustainable development of the environment, and at the same time, the new material of nano-clay has potential application value.

Rheological Findings on Storage Stability for Chemically Dispersed Crumb Rubber Modified Bitumen

2021 ◽  
Vol 305 ◽  
pp. 124768
Author(s):  
Naeem Aziz Memon ◽  
Nur Izzi Md. Yusoff ◽  
Syed Faraz Jafri ◽  
Khawaja Sheeraz
Keyword(s):  
Storage Stability ◽  
Crumb Rubber ◽  
Modified Bitumen

Can crumb rubber modifier effectively replace the use of polymer- modified bitumen in asphalt mixture?

2021 ◽  
pp. 1-16
Author(s):  
Lily D. Poulikakos ◽  
William Buttlar ◽  
Nicolas Schüwer ◽  
Davide Lo Presti ◽  
Tobias Balmer ◽  
...  
Keyword(s):  
Asphalt Mixture ◽  
Crumb Rubber ◽  
Modified Bitumen ◽  
Polymer Modified Bitumen

Quantifying In Situ Tack Coat Performance Using the TackBond Tester for Quality Control

2021 ◽  
pp. 036119812110581
Author(s):  
Blaine M. Wruck ◽  
Erdem Coleri ◽  
Richard Villarreal ◽  
Vikas Kumar ◽  
James Batti
Keyword(s):  
Control Process ◽  
Test System ◽  
Strong Correlations ◽  
Bond Quality ◽  
Test Device ◽  
Bond Performance ◽  
Direct Shear Tests ◽  
Construction Specifications ◽  
Tack Coat

In light of the various quality assurance (QA) issues pertaining to tack coats that occur during construction, there is a need for a means of verifying interlayer bond quality in situ. Despite the immense use of tack coat as a constituent in paving, there are no construction specifications with provisions for the quantification of tack coat bond quality in laboratory or field settings. In this study, a construction QA process for tack coat bond performance was proposed. A novel field tack coat bond strength test device, TackBond, was developed and used for this purpose. The performance of engineered (new tack coat technologies that are tracking less) and conventional tack coats was also evaluated in the laboratory and the field using the developed TackBond test system. The TackBond device was improved in this study by adding features that render it more practical, portable, accurate, and better suited for a variety of pavement surface conditions. Engineered tack coat performance was compared with that of tack coats used conventionally on both milled and overlay surface types. The suitability of the TackBond Test device for capturing the true response of each tack coat was first evaluated by comparing results from TackBond laboratory tests with monotonic direct shear tests (DST) on laboratory-produced samples. Strong correlations between the two test types were achieved. Results of field and laboratory TackBond tests showed that the in situ QA control process developed in this study could be effectively used to improve the in situ tack coat bond performance.

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