Tóm tắt luận Án tiếng anh nghiên cứu Đặc tính cơ học lớp dính bám của kết cấu lớp phủ mặt cầu bê tông xi măng trong Điều kiện việt nam

Objectives This research focuses on examining the shear resistance properties of a bondinh layer at the interface between the concrete bridge deck slab and the asphalt overlay.. It aims

DINH QUANG TRUNG

MECHANICAL PROPERTIES OF BONDING LAYER OF ASPHALT OVERLAY ON CONCRETE BRIDGE DECK

UNDER VIETNAM’S CONDITIONS

MAJOR: Transport Construction Engineering MAJOR CODE: 9.58.02.05

DOCTORAL THESIS

Scientific Supervisors:

1 Assoc Prof., PhD Tran Thi Kim Dang

2 Assoc Prof., PhD La Van Cham

Hanoi, 2024

SUMMARY OF DISSERTATION

1 Summary of dissertation

In Vietnam's road network, bridges form a substantial and steadily increasing component, driven by the country’s rapid development Most bridges in this network are either concrete structures or composite steel girder bridges with reinforced concrete (RC or BTCT- a Vietnamese official abbreviation for reinforced concrete) decks Typically, the RC bridge decks are overlayed with one or two layers of asphalt, with a standard thickness ranging from 50 to 70

mm, and occasionally reaching up to 120 mm

The asphalt overlay on bridge decks in Vietnam tends to deteriorate at a faster rate compared to regular road surfaces In a research project funded by Vietnam Ministry of Transport in 2010 which was implemented by the Institute of Transport Science and Technology, common forms of asphalt damages on bridge decks were addressed [1] Most of the damages are linked to the quality of adhesion between asphalt layer and concrete bridge deck and its deterioration by time The tropical climate of hot, humid, and rainy, exacerbated by recent extreme weather patterns such as prolonged heat and flooding along with increased traffic volumes significantly impacts the overall quality of road pavement, and in particular, the structural integrity of the asphalt overlay on bridge decks, especially those with a thin asphalt layer

As a result, the study of the "Mechanical Properties of Bonding Layer of Asphalt Overlay

on Concrete Bridges Deck under Vietnam’s Conditions" is essential

2 Objectives

This research focuses on examining the shear resistance properties of a bondinh layer at the interface between the concrete bridge deck slab and the asphalt overlay It aims to assess factors influencing the adhesion quality, including fatigue shear properties and the predicted fatigue shear life of the adhesive materials used at interface between asphalt overlay and concrete bridge deck

3 The subject and the scope of research

a) The subject

The research object is the adhesive layer in the pavement structure of asphalt overlay on concrete bridge deck, including conventional cement concrete (BTXM – a Vietnamese official abbreviation for cement concrete) and ultra-high-performance-concrete (UHPC)

The materials for adhesive layer include the one has been used popuparly in Vietnam, is CRS-1P, along with two newer materials: thermoplastic epoxy resin and epoxy bitumen

b) The scope

Various indicators exist for assessing the mechanical properties of adhesive materials of asphalt overlay on the concrete bridge deck However, this study focuses specifically on shear resistance properties, including fatigue shear properties, for the three selected adhesive materials The study does not address mechanical indicators for structural analysis of the asphalt pavement on concrete bridge deck, nor does it involve structural calculation

The study focuses only on concrete bridge decks, simulated using CC and UHPC slabs The studies were conducted exclusively in the laboratory, without any field testing

4 Scientific and practical significance

a) Scientific significance

- Study the operation and failure mechanism of asphalt overlay on concrete bridge decks, the role of adhesive layers in the structure of asphalt overlay on concrete bridge decks Study the shear resistance properties and fatigue shear properties of the adhesive layers in the structure of concrete bridge deck coatings

- Study the factors affecting shear resistance and fatigue life of the adhesive layer in the structure of asphalt overlay on concrete bridge deck

b) Practical significance

- Evaluate and determine the primary factors influencing adhesion quality Conduct a

comparative analysis of the adhesion quality among the different adhesive materials studied

- The research results provide valuable reference information, particularly regarding the shear curve parameters and fatigue shear properties of adhesion materials used in interlayer between asphalt overlay and concrete bridge deck

CHAPTER 1 STUDIES ON ADHESION OF ASPHALT OVERLAY ON BRIDGE DECKS

1.1 Overview of structure of asphalt overlay on concrete bridge deck in Vietnam and around the world

1.1.1 Structure of asphalt overlay on concrete bridge deck

The typical structure of the asphalt coatings on a conventional CC bridge deck [42,43,75]

is as follows:

- CC surface was shot blasted to create roughness

- A permeable epoxy resin layer

- A flexible plastic waterproofing layer

- A tack coat layer

- A double-layer of mastic asphalt mixture -

protective layer and surface coating

Figure 1.1 Structure of asphalt coatings on concrete bridge deck in some Europe countries

In European countries, bridge deck coatings must provide reliable waterproofing protection under all conditions, along with sufficient strength and mechanical durability to withstand traffic loads This includes the compressive and shear forces generated by vehicles during turning, braking, and acceleration The coatings must also resist cracking and spalling under the effects of heat and humidity and maintain both mechanical and chemical durability against loads, weather, and chemical exposure from weathering processes

To date, the asphalt coating structure on CC bridge decks in Vietnam remains relatively simple compared to other countries It typically consists of a single layer of standard adhesive material, such as hot asphalt, liquid asphalt, or asphalt emulsion, made from either conventional

or modified bitumen Typically, the asphalt overlay on CC bridge decks consists of dense asphalt concrete using conventional 60/70 Pen bitumen (AC or BTNC- a Vietnamese official abbreviation for dense asphalt concrete) or modified asphalt concrete (BTNP- a Vietnamese official abbreviation for hot-laid or hot-mix asphalt concrete) with a thickness of 70 mm In some cases, the asphalt overlay consist of only a BTNP layer with minimum thickness of 50

mm or two AC layers, reaching a total thickness of up to 120 mm The overlay structure on Tan

Vu - Lach Huyen bridge deck [10], as described below is representative of the typical overlay assphalt structure on CC bridge decks of large-scale bridges and includes the following:

- 5 cm thick polymer modified asphalt concrete BTNP12.5

- Tack coat of 0.5 kg/m2

- Spray waterproof

Figure 1.2 Asphalt overlay structure on Tan Vu - Lach Huyen bridge deck [10]

1.1.2 Overview of damages of asphalt overlay on concrete bridge decks in Vietnam and

around the world

Damage to asphalt overlay structure is the deterioration of the asphalt concrete layer leading to observable signs of defects that reflect various underlying mechanisms of deterioration

In developed countries like the UK, Germany, Spain, and Italy, asphalt overlay on bridge decks commonly experience two primary types of damage: cracking and deformation, with cracking being the most prevalent Water infiltration through cracks weakens adhesion, leading

to spalling and potholes Deformation occurs when the material structure becomes unstable, resulting in subsidence or heave

In Hong Kong, though designed to last 20 years, the asphalt overlay of many bridges, namely the Ting Kau Bridge, West Kowloon Bridge, Kap Shui Mun Bridge and Ma Wan Bridge, began to fail shortly after being put into operaion In China, in areas with similar conditions to Vietnam, many bridges with asphalt layerNH also failed early After only six months to a year of use, rutting, cracks and spalling began to appear on the bridge decks

In Vietnam, various types of damage are frequently observed not only on bridges that have been in use for some time but also on newly constructed bridges or those recently put into operation Common damages are wheel ruts, cracks and spalling

Figure 1.5 - Wheel ruts on Hoa Binh

bridge (Km84+140, NH10)

Figure 1.6 - Wheel ruts on Kien bridge

(Km20+590, NH 10)

Figure 1.13 - Slippage, cracking and

scaling (Ben Da Bridge - NH1) bridge deck (Dong Yen Bridge- Km25+240) Figure 1.14 - Spalling, potholes on the 1.1.3 Causes and mechanisms of the failures of asphalt overlay on bridge deck

Vietnamese [1] and international studies [35, 53, 77, 83] show that the asphalt overlay on concrete bridge deck is often damaged quickly mainly due to the following reasons:

- Poor quality of tack coat layer due to the bridge deck surface its self quality or poor adhesive performance causes the asphalt overlay debonded

- The horizontal component of vehicle wheel loads generates direct tensile stress on the interface between asphalt overlay and bridge dectk This causes the asphalt concrete layer sliding along the interface, leading to cracking and simultaneously pushing the asphalt layer

debonded from the bridge deck (Figure 1.17)

- Excessive air voids, caused by poor mixture design and/or compaction, allow rainwater

to penetrate and pool at the interface This creates hydrodynamic pressure under vehicle wheels, leading to adhesion loss and peeling of the asphalt overlay

- Elevated temperatures during the summer months weaken the structural integrity of the asphalt layer and the bitumen-based adhesive material The reduced shear resistance of the asphalt mixture makes it susceptible to rutting, while the instability of the tack coat can result in slippage, heave, and spalling of the asphalt overlay

- The asphalt layer exhibits poor thermal stability, resulting in a lack of shear resistance This deficiency can lead to wheel rutting or sliding on the surface

Analysis of the primary causes and damage mechanisms of the asphalt overlay indicates that load and environmental factors are the primary

contributors to these issues

Figure 1.17, adapted from Shahin MY et al

[64], depicts the slippage mechanism that arises from

compromised adhesion between two asphalt concrete

layers This mechanism bears resemblance to the

types of damage observed in asphalt overlay on

bridge decks In two comprehensive studies [64, 66],

Shahin et al delved into the influence of layer

slippage on pavement performance through the

application of diverse mechanical models As

illustrated in Figure 1.17, the passage of a wheel

induces both a normal pressure component, contingent upon the axle load, and a lateral force component This horizontal force compels the asphalt layer to slide along the contact surface, triggering lateral slippage As a consequence of this slippage mechanism, the asphalt mixture may succumb to cracking due to direct tensile forces, ultimately leading to shear cracking Furthermore, at points of weakened adhesion, the asphalt coating mixture is prone to further displacement and dislodgement under the influence of tensile forces perpendicular to the road surface

1.2 Tack Coat in Asphalt Pavements on Concrete Bridge Decks: A Review

1.2.1 A review of domestic research on the influence of tack coat on Interlayer Adhesion

in Asphalt Pavement on Concrete Bridge Deck Systems

While several studies in Vietnam [3, 13] have investigated the adhesion between asphalt concrete layers in flexible pavement structures, research specifically examining the adhesion between asphalt concrete coatings and bridge decks remains limited To date, such research has primarily been conducted within the scope of specific project-based investigations

Topic [1], conducted by the Institute of Transport Science and Technology in 2010, presented and analyzed the damage mechanisms and causes of deterioration in asphalt overlay

on bridge deck The study identified several common damage phenomena, including wheel rutting, heaving, slippage-induced cracking, pothole formation, and surface scaling These issues were directly or indirectly attributed to deficiencies in the adhesion between the bridge deck and the asphalt overlay

In several projects involving the construction and repair of orthotropic steel deck bridges, such as the Thuan Phuoc Bridge and Thang Long Bridge, experimental studies were conducted

to assess the adhesion of bridge deck coatings Despite the support of design testing, these bridge decks still suffered damage, including cracking and slippage, which was attributed to adhesion loss between the asphalt overlay and the bridge deck

Several construction and repair projects involving orthotropic steel deck bridges, such as the Thuan Phuoc and Thang Long bridges, have included experimental studies to evaluate the

Figure 1.17 - Slippage mechanism due to poor adhesion or loss of adhesion between the coating and the

underlying layer

adhesion properties of bridge deck coatings Despite the simulated testing program during design period, these bridges have experienced various forms of damage, including cracking and slippage, which are often linked to a loss of adhesion between the asphalt overlay and bridge desk surface

The Thang Long bridge repair project carried in 2020 incorporated a comprehensive approach, including assessments of bridge damage levels [6], studies on strengthening orthotropic steel slabs with UHPC [7, 4], and research on suitable adhesive materials and asphalt concrete for UHPC overlaying [5] The study involved essential experiments aligned with Japan Highway Association guidelines, such as pull-off test and direct shear test Results showed that thermalplastic Epoxy Resin namely Hyper Prime, demonstrated strong adhesion, even on samples subjected to 15,000 loading cycles in wet wheel tracking test at 50°C and then tested under medium and high temperatures This material was selected as a dual-functional layer providing both waterproofing and adhesion for asphalt overlay using PMB3 bitumen The findings from these experiments, along with the wet wheel tracking test simulated actual exploitation conditions of asphalt overlay on UHPC bridge deck serve as a foundation for this thesis research, which examines factors affecting the adhesion properties of bonding layer in bridge deck overlay structure

1.2.2 A review of international research on interfacial adhesion and adhesive materials in

pavement on bridge deck

While numerous international studies have explored the adhesion between asphalt concrete layers in pavement structures, research specifically focused on asphalt overlays on concrete bridge decks remains limited

For asphalt overlays on Ultra-High-Performance Concrete (UHPC) bridge decks, a limited number of studies, primarily conducted by Chinese researchers (e.g., [51]), have been published These studies primarily focus on structural solutions to enhance the stiffness of existing orthotropic steel bridge decks through UHPC reinforcement, but the adhesion between the asphalt overlay and the UHPC layer has not been extensively investigated In practical applications, Stone Mastic Asphalt (SMA) with polymer-modified bitumen binders and epoxy resin bonding agents is frequently employed for overlays on UHPC-strengthened orthotropic steel bridge decks

Recent studies have also delved into the realm of bonding materials, particularly those used between asphalt overlays and concrete bridge decks For instance, study [81] addresses the following objectives:

 Modification of materials to enhance the shear resistance of asphalt overlays on bridge decks

 Analysis of the mechanical behavior of asphalt overlay structures, including the

examination of the relationship between normal stress and shear stress at the interface using finite element methods (FEM)

 Determination of shear failure parameters based on shear strength limits

 Development of a calculation method to control the adhesion of asphalt overlays on concrete bridge decks

The authors investigate the potential for shear failure of the asphalt layer on concrete bridge decks using Finite Element Method (FEM) and compare the results with those obtained from other analytical software The shear strength of asphalt concrete is employed to assess shear failure at the interface between the asphalt layer and the concrete deck

Other researcher [83] focused on the adhesion between the concrete surface and the asphalt overlay, specifically analyzing how surface roughness of the concrete layer influences direct shear strength This research enabled the establishment of an optimal adhesion water ratio based on surface roughness

In another study [48], researchers examined the quality of waterproofing under temperature variations using microscopic analysis and evaluated the fatigue resistance of the

composite bridge deck and asphalt overlay

A publication in 2020 [29] further investigated the effect of UHPC surface roughness on the adhesion of the asphalt overlay This study utilized shot blasting technology to roughen the UHPC surface prior to applying bonding and asphalt layer Simultaneous shear strength testing and digital image analysis were employed to assess surface roughness, providing insights into the relationship between surface roughness and adhesion strength

1.2.3 Adhesive materials for asphalt overlay on concrete bridge deck in Vietnam

Vietnam currently employs a variety of adhesive materials for asphalt overlays on concrete bridge decks, including hot bitumen, cut-back asphalt, asphalt emulsion, and polymer asphalt emulsion The Thang Long Bridge deck repair project uniquely utilized a thermoplastic epoxy resin (Hyper Prime) However, Vietnam lacks a standardized national guideline for adhesive materials in bridge deck asphalt overlays, particularly for concrete decks Current bridge construction projects often specify adhesive materials in Technical Specifications, providing limited details beyond material type and usage rate

1.3 Studies on shear and fatigue properties of the tack coat between pavement layers and bridge deck coatings

Fatigue analysis of materials typically examines the relationship between stresses and the resulting strains in specific locations, as influenced

by the number of load cycles

Figure 1.20 presents a displacement-load

cycle curve adapted from the research of Cristina

Tozzo et al [38] This characteristic curve shape is

commonly observed in fatigue shear studies across

diverse temperature ranges and load thresholds

Fatigue curve equations can be derived using

regression analysis, customizing the regression

model to specific experimental conditions and

parameters These equations can incorporate a range

of dependent and independent variables, tailored to the specific analysis needs

As outlined in [38], the shear stiffness modulus of the adhesive material at each load cycle within a fatigue shear test can be computed using formula (1.4), incorporating the phase angle calculated for that specific cycle:

𝐾∗ = ∆

∆ 𝑒 (1.4)

herein:

𝐾∗ - Shear stiffness modulus of the bond

layer at the ith load cycle, MPa/mm

∆𝜏 - Shear stress magnitude at the ith force

cycle, MPa

∆𝑢 - displacement measured within the

adhesive layer at the ith force cycle, mm

𝜑 - phase angle between force and

displacement

The shear stiffness modulus can be calculated

and plotted against the number of loading cycles

The fatigue life is determined as the number of

loading cycles corresponding to the moment when

the stiffness decreases by 50%, i.e., approximately

in the middle of stage 2, called N50 (See Figure

1.21)

Shear stiffness analysis from fatigue shear

Figure 1.20 - Curve of relationship between number of load cycles and

test considering phase angle was also performed by M Diakhaté et al [54] to study the adhesive bond between two asphalt concrete layers Similarly, at each force cycle, the shear stiffness of the adhesive layer can be determined as a complex number:

The energy dissipated in each force cycle

can be calculated by the formula:

𝑊 = 𝜋 ∗ 𝜎 ∗ 𝜀 ∗ sin ∅ (1.10)

herein:

𝑊 - energy dissipated in cycle i

𝜎 - stress level in cycle i

𝜀 - strain rate in cycle i

∅ - Phase (lag) angle in cycle i

Research [68] established a method for

estimating fatigue life based on the cumulative

rate of dissepted energy change The concept of

the ratio of dissipated energy change (RDEC) and

the fatigue analysis method based on RDEC were

proposed by Carpenter and Jansen in the fatigue

study of hot mix asphalt concrete used for airport

pavements [33] and then expanded by Ghuzlan in

his doctoral thesis [45] and continued to be

confirmed by Carpenter and colleagues [34] for

its correctness and applicability

herein:

RDEC - ratio of dissipated energy change

𝐷𝐸 - energy dissipated in the force cycle n

𝐷𝐸 - energy dissipated in the force cycle (n +1)

1.4 Research issues and thesis content

This research investigates the adhesion properties of asphalt overlay on concrete bridge decks, focusing on three specific types of adhesive materials It aims to identify factors influencing adhesion and to develop fatigue shear test models for evaluating the service life of the bonding layer in asphalt overlay structure on concrete bridge deck Ultimately, the research seeks to determine the fatigue life of the adhesion layer

1.5 Research methodology

This research employs a combined theoretical and experimental approach:

Figure 1.26 - Loading and unloading curves in repeated loading tests with viscoelastic materials at different loading

cycles

Figure 1.27 - Curve between RDEC and number of force cycles with three distinct

stages

 Experimental Study: Conducting direct shear tests under various experimental

conditions simulating actual operating conditions in Vietnam to investigate the adhesion layer properties

 Model Development and Testing: Constructing a model and performing repeated shear tests to assess the fatigue life of the adhesive layer

 Data Analysis and Modeling: Analyzing data to identify influential factors and utilizing regression analysis to develop a fatigue shear equation, enabling the prediction of the adhesive layer's fatigue life in concrete bridge deck coating structures

CHAPTER 2 EXPERIMENTAL MODELS AND RESEARCH PROGRAM

DEVELOPMENT 2.1 Global shear test models and their application in the thesis

2.1.1 2.1.1 Overview of experimental Models for adhesion and adhesion loss studies

Numerous experimental models exist for evaluating factors influencing adhesion and adhesion loss between asphalt concrete layers in pavement structures and between asphalt overlay on concrete pavement surfaces or bridge decks The Leutner shear test is a widely recognized and frequently used model, applied in numerous studies [61, 69, 46]

2.1.2 2.1.2 Dynamic load shear test models

Repeated or dynamic loading is essential for more accurately simulating the effects of traffic on pavement structures Shear tests are commonly used to evaluate interlayer bonding within pavement structures, especially in the context of asphalt layers on concrete bridge decks These tests often incorporate dynamic loads, and three primary experimental models are employed: direct plane shear, indirect plane shear from vertical loads, and torsional tests

The dynamic version of the Leutner shear test is a widely used method for dynamic shear testing This test has been adopted in numerous studies [30, 49] to measure the adhesion coefficient between layers, which is crucial for inputting data into pavement structure analysis software

A well-known experimental approach, developed by Romanoschi and Metcalf [59] in

1999, is the Shearing Fatigue Test (SFT), which examines the adhesion properties between asphalt concrete layers In this test, a cylindrical sample comprising two asphalt concrete layers—bonded with different adhesives or adhesive materials—is subjected to dynamic

loading at a 25.5° angle relative to the sample's longitudinal axis The test generates a dynamic shear force equivalent to half of the normal stress applied In 2007, the first plane shear model, originally proposed by Uzan, was further refined by a research group at the University of Nottingham [55] to include repeated loading and normal force input, enhancing its applicability for testing pavement performance under dynamic conditions

The third experimental model is the torque test, which evaluates the impact of repeated forces on adhesive layers Collop et al [36] developed an automatic torsional adhesion testing device capable of applying either a constant torque or a constant torsional strain rate, making it

Figure 2.2 - Leutner shear test with dynamic loading

useful for studying the long-term effects of dynamic loading on adhesion strength

2.1.3 2.1.3 Experimental shear model used in experimental research of the thesis

The necessary models and equipment for adhesion research are currently available in Vietnam, specifically within the research facilities of the University of Transport and Communications This includes a Leutner shear test apparatus, which employs a constant shear rate to investigate the shear resistance properties of adhesive materials and the factors influencing them

While dynamic shear models are not yet available in Vietnam, research has been conducted on the installation of dynamic loading equipment [24], as demonstrated in a study on irreversible deformation of asphalt concrete using dynamic load creep tests [14] The direct shear test, based on the Leutner model, can be combined with this dynamic loading system to create a dynamic shear test model, which the researcher will utilize to study the fatigue properties of adhesive materials for asphalt overlay on concrete bridge decks

2.1.4 2.1.4 Properties of main materials in bridge deck overlay used in the study

The adhesive materials investigated, as outlined in the experimental research program in Chapter 2, include: CRS-1P polymer bitumen emulsion, Epoxy bitumen (BE), and Epoxy Hyper Prime (HP) The properties of the CRS-1P bitumen emulsion meet the current standards [17], and the basic properties of BE and HP are according to the technical documents of the supplier [70, 71] and the research [21] The BTXM and UHPC concrete slabs simulating the bridge deck were cast in the factory according to the actual project technical specifications, respectively [9] and [8]

Slab specimen preparation procedure:

BTXM and UHPC Slabs: Slabs with dimensions L x B x h = 320 mm x 260 mm x 40 mm were cast and cured under moist conditions (for BTXM) and moist-hot conditions (for UHPC) until they reached 28 days of age

After curing and achieving the desired strength, the surfaces of both types of slabs were roughened by shot blasting or grooving

Bonding Layer: A dual-function bonding layer consisting of thermoplastic epoxy resin and epoxy bitumen was applied to the specimen surfaces according to predetermined ratios The application rate for the epoxy resin was based on the supplier's recommendations [70] The application rate for BE was determined based on pull-off test results

Testing: Pull-off tests were conducted directly on the slabs, or cylindrical cores were drilled from the slabs for shear testing

2.1.5 2.1.5 Design and assembly of the fatigue shear test equipment

The fatigue shear test equipment was constructed by combining a Leutner shear device and a dynamic loading system The Leutner shear model does not have a normal load and is subjected to a cyclic shear load with a selected loading cycle High temperature is controlled using a heating chamber with hot air and an automatic on/off system to maintain the temperature

The experimental setup can be used to study

the fatigue shear properties through a diagram

showing the number of load cycles versus the

measured shear displacement at the interface

between two asphalt concrete layers, between the

asphalt concrete layer and the cement concrete

layer, or between the asphalt concrete layer and a

steel plate under selected temperature, shear force,

frequency, and loading time conditions Figure 2.14 - Heat transfer model on

bridge deck structure

2.2 Operating conditions of BTXM bridge deck overlays in Vietnam

Numerous studies in Vietnam have investigated the temperature distribution within flexible pavements [7, 22, 24], revealing that asphalt layer temperatures can reach 60°C when the air temperature is 40°C or higher However, there has been no research on the temperature

at the bond layer or within the concrete bridge deck overlay The heat transfer model for a bridge deck overlay differs from that of a pavement structure (Figure 2.14)

In this study, the researcher conducted temperature measurements on the polymer asphalt overlay of the Thang Long Bridge Temperature sensors were placed on the surface of UHPC which reinforced the steel bridge deck, before the polymer asphalt layer was applied Both the surface temperature of the overlay and the air temperature at the height of 1 meter above the pavement surface were measured for comparison The results of the temperature monitoring over time are shown in Figure 2.16

Figure 2.16 - Temperature at the bottom of the bridge deck overlay - bond layer, on the

surface of the asphalt concrete overlay, and air temperature 2.3 The standards and technical specifications used to evaluate the adhesion between two layers of pavement material or the adhesion of the asphalt overlay on bridge deck

2.1.6 2.3.1 Japanese testing standards

The Japan Road Association's Manual for Waterproofing Bridge Decks [11] is a technical guide for controlling the interaction between waterproofing and adhesion between the bridge deck and the asphalt overlay The technical specifications related to adhesion evaluation in this standard include pull-off test and shear test

The pull-off test is performed on a slab samples cast by the roller compaction method The shear test checks the shear strength between the bridge deck and the asphalt overlay The testing sample is a square slab tested at 23 ± 20°C and -10 ± 20°C The shear rate is 1mm/min

2.1.7 2.3.2 Chinese testing standards [56]

Epoxy is commonly used in bridge deck overlay in China for waterproofing and adhesion The test was carried out on insulated samples under conditions of (23 ± 20°C) and relative humidity (45-70%) Shear test was carried out using an inclined shear model at 50°C

2.1.8 2.3.3 AASHTO/ASTM testing standards

The adhesion between two pavement layers can be tested by shear and pull-off tests according to American standards: standardized pull-off test [26] and shear test according to AASHTO standards [27]

2.4 Experimental study to evaluate factors affecting the bond quality of concrete bridge deck overlays

Experimental model

Pull-off test - recommended to determine the best adhesion water content Test standard according to AASHTO [26]

- Direct shear test according to Leutner shear model - study the influence of factors on adhesion of bridge deck coatings Test standard according to AASHTO [27], without normal stresses

Adhesive materials

03 types of materials selected for the experiment include:

- The combination of spray waterproofing material + emulsion adhesion CS1-P, is a typical structural combination in practice in Vietnam for asphalt coating on concrete bridge decks

- The dual-function material layer (waterproofing + adhesion) is made of Epoxy asphalt (EA) with the ratio of asphalt 60/70 and two-component epoxy resin is 50:50

- The material layer combines two functions of waterproofing + adhesion with thermoplastic Epoxy resin

The above waterproofing combinations are applied to 02 types of materials corresponding

to the cement concrete bridge deck: conventional CC and UHPC slabs

The asphalt concrete coating of the bridge deck is polymer asphalt concrete, using asphalt with polymer additives PMB1

Bonding Materials

Three types of materials were selected for the experiment:

Combination of sprayed waterproofing material and CS1-P emulsion bonding: This is a typical structural combination used in Vietnam for asphalt overlays on concrete bridge decks Dual-function of waterproofing and bonding materials using epoxy asphalt (BE) with a 60/70 asphalt ratio and a two-component epoxy resin ratio of 50:50

Combination material with dual functions of waterproofing and bonding using thermoplastic epoxy resin

Concrete bridge deck materials:

Conventional concrete slab

UHPC slab

Asphalt Overlay

The bridge deck overlay is a polymer asphalt concrete using PMB1 polymer-modified asphalt

Number of Test Specimens

The groups of specimens and their quantities are summarized in the tables 2.10

Table 2.10 - Number of slabs tested according to material combinations and distribution

of wheel track test specimens

Number of slabs used for shear test and fatigue shear test slabs for pull-Number of

off test

Total Number

of slabs speciment

No wheel wheel With