- Email: [email protected]
Study on water permeability, shear and pull-off performance of waterproof bonding layer for highway bridge
Accepted Manuscript Study on Water Permeability, Shear and Pull-Off Performance of Waterproof Bonding Layer for Highway Bridge Meng Guo, Yiqiu Tan, Linbing Wang, Zhoujing Ye, Yue Hou, Jiangfeng Wu, Hailu Yang PII: DOI: Reference:
S1996-6814(17)30041-X https://doi.org/10.1016/j.ijprt.2017.09.013 IJPRT 129
To appear in:
International Journal of Pavement Research and Technology
Received Date: Revised Date: Accepted Date:
1 March 2017 29 August 2017 18 September 2017
Please cite this article as: M. Guo, Y. Tan, L. Wang, Z. Ye, Y. Hou, J. Wu, H. Yang, Study on Water Permeability, Shear and Pull-Off Performance of Waterproof Bonding Layer for Highway Bridge, International Journal of Pavement Research and Technology (2017), doi: https://doi.org/10.1016/j.ijprt.2017.09.013
This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
Study on Water Permeability, Shear and Pull-Off Performance of Waterproof Bonding Layer for Highway Bridge Meng Guo1, Yiqiu Tan2, *, Linbing Wang3, Zhoujing Ye4, Yue Hou5, Jiangfeng Wu6, and Hailu Yang7 1
Assistant Professor (Ph.D.), National Center for Materials Service Safety, University of Science and Technology Beijing, 30 Xueyuan Road, Haidian District, Beijing, China; Ph (010) 62321017-613; email: [email protected] 2 Professor (Ph.D.), School of Transportation Science and Engineering, Harbin Institute of Technology, 73 Huanghe Road, Nangang District, Harbin, China; email: [email protected] 3 Professor (Ph.D.), Joint USTB-Virginia Tech Lab on Multifunctional Materials, USTB, Beijing, Virginia Tech, Blacksburg, VA 24061, United States; email: [email protected] 4 Graduate Research Assistant, National Center for Materials Service Safety, University of Science and Technology Beijing, Beijing, China; email: [email protected] 5 Associate Professor (Ph.D.), National Center for Materials Service Safety, University of Science and Technology Beijing, Beijing 100083, China; email: [email protected] 6 Graduate Research Assistant, National Center for Material Service Safety, University of Science and Technology Beijing, Beijing 100083, China; email: [email protected] 7 Graduate Research Assistant, National Center for Materials Service Safety, University of Science and Technology Beijing, Beijing, China; email: [email protected]
ABSTRACT The performance of waterproof bonding layer directly effects the durability of the highway bridge. Water permeability, shear strength and tension strength are three main indicators evaluating the waterproof bonding layer. In this research, three waterproof bonding materials including SBS modified asphalt, SBR modified asphalt emulsion and second order reaction waterproof material were selected. The water permeability, shear strength and pull-off strength were tested. The effect of different temperature and different contents were analyzed. Results show that: the water permeability resistance of waterproof bonding layer ranked as follows: SBS modified asphalt > Second order reaction waterproof material > SBR modified asphalt emulsion. Compared to SBR modified asphalt emulsion and Second order reaction waterproof material, SBS modified asphalt has a better shear resistance. Three waterproof *
- Corresponding author
materials used in this research all have temperature sensitivity. Their shear strength and tension strength decrease dramatically with temperature increasing. KEY WORDS Waterproof Bonding Layer, Highway Bridge, Water Permeability, Shear Performance, Pull-Off Performance
1. INTRODUCTION The performance of waterproof bonding layer in highway bridge directly influence the durability of the bridge structure. In recent years, how to choose the proper materials and design the waterproof bonding layer with excellent performance has attracted more and more attention. Existing studies show that the performance of waterproof bonding layer has a close relationship with the early distresses of bridge made of asphalt mixture. The damage of bridge paving has two types: one is the adhesion force between paving layer and bridge is too weak so that it’s easy for slippage or delaminating to happen between different layers. The other damage type is due to the weak water permeability of adhesion layer. The rain permeates through gaps and cracks into bridge, flushes the concrete, corrodes steel bar to decrease the service life of concrete bridge. So it is necessary to set a waterproof bonding layer to prevent these damages. In 1920, Danish first began to use concrete bridge deck waterproofing layer. With the development of highway and the study of researcher from various countries, bridge waterproofing bonding layer has been recognized around the world and attracted widespread attention. In 1970s, the waterproofing bonding layer was widely used in European and American countries. In July of 1972, fourteen countries from International Organization for Economic Cooperation and Development (OECD) jointly issued a research report on “concrete bridge deck waterproofing”. This report summarized each country's bridge deck waterproofing situation and the used methods, and systematically studied the bridge deck waterproofing membrane material used in each country. It also proposed a detailed specification about how to test the waterproofing bonding materials [1-5]. In 1976, United States Highway Cooperative Research Organization (National Cooperative Highway Research Program) published a bridge deck waterproofing report, which stated in detail the evaluation method of indoor waterproofing membrane performance. In 1995, based on the long-term testing and research of the concrete bridge deck waterproofing materials, a new construction, renovation, maintenance view point of bridge deck waterproofing system was proposed. In the early of 1950s, British TRRL (Transport and Road Research Laboratory) did a lot of research on bridge paving, especially for the water permeability, interlayer shear Performance of Waterproof Bonding Layer for Highway Bridge [6-9]. Guo et al. studied the interfacial adhesion property between asphalt binder and aggregate by conducting multiscale tests. They found the properties of materials and curing condition have a significant impact on the interfacial performance between asphalt binder and aggregate [10-16]. Though the interfacial behavior has been studied by multiscale test and numerical simulation, the real macro situation still has a distance to the theoretical model [17-18]. Some relevant tests are necessary to be conducted. In this research, the water permeability, shear performance and pull-off performance of three waterproof bonding materials are studied, and the effect factors are analyzed. 2. MATERIALS AND METHODS 2.1 Water Permeability The test device for water permeability used in this research was permeameter for structure layer material (Figure 1). This device consists of gas-pressure meter, fixed base, upper and lower clamping bolt and pressure plates with a pressurized cylinder. In order to prevent leaking, seal rings were used at the upper and lower pressurized plates, and bolts were used to
fasten the pressurized plates.
Figure 1. Permeameter for structure layer material The pressurized tube inner diameter of Material Permeability Tester was 100mm, the maximum water pressure is 0.7MPa. The specimen was "cement concrete + asphalt concrete" composite rolled using wheel tracking apparatus. The specification and number of mineral aggregates met the specification "Highway Engineering asphalt and asphalt testing procedures" (JTJ052-2000) in T0703-1993. Three different waterproof bonding materials between two layers were tested. The test methods and procedure were as follows: (1) Brush the waterproof bonding material on 30cm × 30cm sample surface twice to the optimum amount. Within 5 hours after first layer is completely dry, brush the second layer and treat the surface smooth by adjusting the brush force. Keep them at room temperature for 48 hours. (2) Put the waterproof bonding material into rutting sample mould with size 30cm×30cm×5cm. Use the rolling compaction method to mold the specimen, which consists of two layers “cement concrete + asphalt concrete”. One day later, demould it. (3) Placed the penetration instrument on a solid flat surface. Clean the specimen and put it in the middle of the base with the face of the waterproof layer upward. (4) Smear the butter around the pressing plate. Put the pressurized plate on the specimen and ensure the pressure plate and the base alignment. (5) Link the base and the pressing plate closely together by using the lower clamping bolt. (6) Use a bolt to link the pressurized plate and pressurized cylinder tightly. (7) Pour water into the pressurized cylinder until 2/3 volume. (8) Drop a few drops of red ink into the water, and then start the machine. Add air pressure into the pressurized cylinder to the regulations, and then keep them for 30 mins. (9) Observe the water permeability status of specimen, and record the time of water seepage. (10) When the test was done, open the pressurizes the valve to release the pressure to zero. Discharge the water in the pressurized cylinder, and then remove the specimen. Clean the machine for the further text.
2.2 Shear Performance The rut plate was used to mold test specimens. The cement concrete plate with size 30cm×30cm×5cm was obtained first, and then the surface was roughed, followed by seven days curing. Polish off the floating pulp on the surface of complete dried cement concrete, brush waterproofing bonding layer, and then pave asphalt concrete layer with thickness 5 cm. At last, wheel grinding instrument was used to mold the specimen. After 48 hours, the mould was released. Coring machine was used to get a 100mm × 100mm double layer specimen. Structure material electric shear apparatus was used to study the shear performance. The study program is shown in Table 1. The effects of waterproof materials type, test condition and material contents on shear strength resistance are mainly studied.
Effects Temperature Materials types Materials content
Table 1. The program for shear performance tests Levels 25℃、40℃、60℃ SBS modified asphalt、SBR modified asphalt emulsion、Second order reaction waterproof material 2 0.6 kg/m 、,1.0 kg/m2、1.5 kg/m2、2.0 kg/m2
2.3 Pull-Off Performance The pull-off test sample size is similar with the shear test samples. The molding method is same with that in section 2.2. The structure materials strength tester was used to study the tension performance in this research. The surface of two specimens should be clean before testing, and then epoxy resin was used to adhere the specimen and mold together. Keep them at room temperature for 24 hours until the epoxy resin solidified completely. In this research, the tension rate was set as 20 mm/min. Two temperatures 25 oC and 60 oC were selected and three different waterproofing bonding materials were studied. 3. RESULTS AND DISCUSSION 3.1 Water Permeability The water permeability resistance of waterproof bonding layer was shown in Table 2. It can be seen from Table 2 that the water permeability resistance of waterproof bonding layer tested in this research ranked as follows: SBS modified asphalt > Second order reaction waterproof material > SBR modified asphalt emulsion. For the waterproof bonding layer of the highway bridge, a good performance should be able to resist water leaking after paving the asphalt mixture and road roller rolling. However, it’s easy for the moisture damage to happen in the asphalt pavement due to the raining, traffic, and other environment effects. When the adhesion between asphalt binder and mineral aggregate is weak, or the void content
is high, or the compaction degree is small, the moisture damage will become worse. The moisture damage can further lead to potholes, slurry pump etc. So the function of waterproof bonding layer is to prevent the outsider water leaking into the inside of the bridge concrete to avoid the moisture damage.
Water pressure （MPa）
Table 2. Test results of water permeability resistant. Waterproof bonding layer Water seepage situation
0.1
SBR modified asphalt emulsion
No water seepage within 30 mins
0.1
SBS modified asphalt 0.3
No water seepage within 30 mins
0.1 0.2 0.2 0.2 0.3
Second order reaction waterproof material SBR modified asphalt emulsion
No water seepage within 30 mins No water seepage within 30 mins
SBS modified asphalt 0.3
No water seepage within 30 mins
Second order reaction waterproof material SBR modified asphalt emulsion
0.3
SBS modified asphalt 0.3
0.3
Second order reaction waterproof material
No water seepage within 30 mins Water started to leak at 10 mins, and leak became worse at 20 mins. No water seepage within 30 mins Water started to leak at 25 mins, and leak became worse at 35 mins.
3.2 Shear Performance The shear stress can be calculated in Equation (1). τ
F S
(1)
Where, τ——shear stress (MPa); F——shear force (N); S——Shear area (m2). (1) Effect of waterproof bonding layer content on the shear performance of interlayer The contents of waterproof bonding layer were selected as 0.6kg/m2，1.0kg/m2，1.5kg/m2， 2.0kg/m2. The test results are shown in Figure 2.
Shear strength τ (MPa)
0.6 0.5 0.4 0.3 SBS modified asphalt SBR modified asphalt emulsion Second order reactio waterproof material
0.2 0.1 0 0
0.5 1 1.5 2 Content of waterproof bonding layer (kg/m2)
2.5
Figure 2. Shear strength of waterproof bonding layer with different materials. It can be seen from Figure 2 that with the increasing of the waterproof bonding material content, the shear strength increases first, and then decreases. Based on the tested data, we can obtain the fitting equation of shear resistant strength for SBS modified asphalt as follows: τ＝-0.097X2+0.31X+0.30 R2＝0.89 Where, τ —— the shear resistant strength (MPa). X ——the content of waterproof bonding material (kg/m2).
(2)
When X=1.50, the shear strength reached maximum. Similarly, the fitting equation of shear resistant strength for second order reaction waterproof material can be shown in Equation (3). τ＝-0.19X2+0.54X+0.10
R2＝0.90
(3)
When X=1.40, the shear strength of second order reaction waterproof material bonding layer reached maximum. The fitting equation of shear resistant strength for SBR modified asphalt emulsion waterproof material can be shown in Equation (4). τ＝-0.01X2＋0.04X+0.36
R2＝0.93
(4)
When X=1.61, the shear strength of SBR modified asphalt emulsion waterproof material bonding layer reached maximum. It can be seen from Figure 2 that when the content of waterproof bonding material is little, the waterproof bonding layer would form a discontinuous thin film, which decreases the shear strength. When the content of waterproof bonding material is too much, the
frictional resistance between different layers is decreased. Therefore, there should be an optimum content of water proof bonding materials to balance the interlayer adhesion and interlayer friction. (2) Effect of test temperature on shear strength of waterproof bonding layer In this research, three test temperatures were seltected: 25 oC, 40 oC and 60 oC. The optimum contents of waterproof bonding materials were applied to study the shear strength. The tests results are shown in Figure 3. 0.6 Shear strength τ (MPa)
0.5
25℃
40℃
60℃
0.4 0.3 0.2 0.1 0 SBS modified asphalt
SBR modified asphalt emulsion
Second order reaction waterproof material
Figure 3. The shear strength of waterproof bonding materials at different temperatures. It can be seen from Figure 3 that the shear performance of waterproof bonding material depends on the temperature significantly. With the temperature increases, the shear strength of three waterproof bonding materials decreases dramatically. When the temperature rose from 25 oC to 40 oC, the shear strength decreased by around 80%. With the temperature further increased to 60 oC, the shear strength dropped to 10% of that at 25 oC. The shear resistance of SBR modified asphalt emulsion has the most temperature sensitivity, followed by second order reaction waterproof material. The SBS modified asphalt has the least temperature sensitivity. 3.3 Pull-Off Performance The tension stress can be calculated as Equation (5). P=
F S
Where, P—Adhesion strength（MPa）； F—Tension force（N）； S—Area of fracture surface（mm2）。 Test results are shown in Figure 4.
(5)
0.6
No waterproof bonding layer
Shear strength τ (MPa)
0.5
SBS modified asphalt SBR modified asphalt emulsion
0.4
Second order reaction waterproof material 0.3
0.2
0.1
0 25
60 Temperature（℃）
Figure 4. The adhesion strength of different materials at different temperatures. It can be seen from Figure 4 that at 25 oC, the adhesion performance of three waterproof bonding materials ranks as follows: SBS modified asphalt > Second order reaction waterproof material > SBR modified asphalt emulsion > No waterproof bonding layer. SBS modified asphalt has a good temperature sensitivity. If the content of SBS modified asphalt is proper, it will form an adhesion layer with good tension performance on the surface of cement concrete. The asphalt based waterproof bonding materials all have temperature sensitivity. With the temperature increasing, not only the shear performance decreases dramatically, but also the tension adhesion performance declines significantly. It can be seen from Figure 4 that the tension strength at 60 oC was much lower than that at 25 oC. At 60 oC, the tension strength were all more than 0.4 MPa, but when the temperature rose to 60 oC, it decreased to 0.1 MPa, which is only 3%~20% of that at 25 oC. 4. SUMMARY OF FINDINGS In this research, three waterproof bonding materials were studied. The water permeability resistance, shear strength resistance and tension strength resistance were investigated. And the effect factors were analyzed. The followings are the other main findings from this study: (1) Compared to SBR modified asphalt emulsion and Second order reaction waterproof material, SBS modified asphalt has a better water permeability resistance. (2) The shear resistance of three waterproof materials ranks as follows: SBS modified asphalt > Second order reaction waterproof material > SBR modified asphalt emulsion. (3) Three waterproof materials used in this research are all temperature dependent. Their shear strength and tension strength decrease significantly with temperature increasing.
ACKNOWLEDGMENTS This study was supported by China Postdoctoral Science Foundation (2016M600926), Beijing Natural Science Foundation (8174071), and Fundamental Research Funds for the Central Universities (FRF-TP-16-039A1). REFERENCES [1] Waterproofing of Concrete Bridge Decks. Organization for economic cooperationnd development. 1972: 58-62. [2] MARTINELLIP. Bridge deck waterproof membrane evaluation. Alaska: State of Alaska Department of Transportation and Public Facilities. 1996, 19 (3): 53-60. [3] F. Seible, C. T. Latham. Horizontal Load Transfer in Structural Concrete Bridge Deck Overlays [J]. Journal of Structural Engineering. 1993, 21: 63-66. [4] Cedergren Water. Key Cause of Pavement Failure. Civil Engineering, American Society of Civil Engineers. 1974, 9: 78-82. [5] NCHRP Synthesis of Highway Practice 220, Waterproofing Membranes for Concrete Bridge Decks, Transportation Research Board, National Research Council, Washington, D. C. 1995: 18-24. [6] NCHRP. Waterproofing Membranes for Protection of Concrete Bridge Decks-Laboratory Phase. NCHRP 1976: 19-23. [7] L.CARR, B.VALLERGA. Nator Proof Membrances For Protertion of Concrete Bridge Decks. 1993: 43-48. [8] PRIC.A.R. Waterproofing of Concrete Bridge Decks Site Practice and Failures. TRRL, Report No. RR317. 1991: 57-60. [9] PRICE.A.R. Laboratory Tests on Waterproofing Systems for Concrete Bridge Decks. TRRL. 1990: 35-39. [10] Guo M, Tan YQ, Zhou SW. Multiscale Test Research on Interfacial Adhesion Property of Cold Mix Asphalt. Construction and Building Materials, 2014, 68: 769-776. [11] Guo M, Motamed A, Tan YQ, Bhasin A. Investigating the Interaction between Asphalt Binder and Fresh and Simulated RAP Aggregate. Materials & Design, 2016, 105: 25-33. [12] Tan YQ, Guo M. Using Surface Free Energy Method to Study the Cohesion and Adhesion of Asphalt Mastic. Construction and Building Materials, 2013, 47: 254-260. [13] Tan YQ, Guo M. Micro- and Nano-characteration of Interaction between Asphalt and Filler. Journal of Testing and Evaluation, 2014, 42 (5): 1089-1097. [14] Guo M, Bhasin A, Tan YQ. Effect of Mineral Fillers Adsorption on Rheological and Chemical Properties of Asphalt Binder. Construction and Building Materials, 2017, 141: 152-159. [15] Guo M, Tan YQ, Yu JY, Hou Y, Wang LB. A Direct Characterization of Interfacial Interaction between Asphalt Binder and Mineral Fillers by Atomic Force Microscopy. Materials and Structures, 2017, 50: 141. [16] Guo M, Tan YQ, Hou Y, Wang LB. Diffusion of Asphaltene, Resin, Aromatic and Saturate Components of Asphalt on Mineral Aggregates Surface: Molecular Dynamics Simulation. Road Materials and Pavement Design, 2017, 18 (S3): 149-158.
[17] Hou, Y., Sun, W., Wang, L., Huang, Y., and Guo, M. A Multi-scale approach of Mode I Crack in ettringite. Road Materials and Pavement Design, 2017, 18(S3): 33-42. [18] Hou, Y., Wang, L., Wang, D., Liu, P., Guo, M., and Yu, J. Characterization of Bitumen Micro-mechanical Behaviors Using AFM, Phase Dynamics Theory and MD Simulation. Materials, 2017, 10(2): 208.
S1996-6814(17)30041-X https://doi.org/10.1016/j.ijprt.2017.09.013 IJPRT 129
To appear in:
International Journal of Pavement Research and Technology
Received Date: Revised Date: Accepted Date:
1 March 2017 29 August 2017 18 September 2017
Please cite this article as: M. Guo, Y. Tan, L. Wang, Z. Ye, Y. Hou, J. Wu, H. Yang, Study on Water Permeability, Shear and Pull-Off Performance of Waterproof Bonding Layer for Highway Bridge, International Journal of Pavement Research and Technology (2017), doi: https://doi.org/10.1016/j.ijprt.2017.09.013
This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
Study on Water Permeability, Shear and Pull-Off Performance of Waterproof Bonding Layer for Highway Bridge Meng Guo1, Yiqiu Tan2, *, Linbing Wang3, Zhoujing Ye4, Yue Hou5, Jiangfeng Wu6, and Hailu Yang7 1
Assistant Professor (Ph.D.), National Center for Materials Service Safety, University of Science and Technology Beijing, 30 Xueyuan Road, Haidian District, Beijing, China; Ph (010) 62321017-613; email: [email protected] 2 Professor (Ph.D.), School of Transportation Science and Engineering, Harbin Institute of Technology, 73 Huanghe Road, Nangang District, Harbin, China; email: [email protected] 3 Professor (Ph.D.), Joint USTB-Virginia Tech Lab on Multifunctional Materials, USTB, Beijing, Virginia Tech, Blacksburg, VA 24061, United States; email: [email protected] 4 Graduate Research Assistant, National Center for Materials Service Safety, University of Science and Technology Beijing, Beijing, China; email: [email protected] 5 Associate Professor (Ph.D.), National Center for Materials Service Safety, University of Science and Technology Beijing, Beijing 100083, China; email: [email protected] 6 Graduate Research Assistant, National Center for Material Service Safety, University of Science and Technology Beijing, Beijing 100083, China; email: [email protected] 7 Graduate Research Assistant, National Center for Materials Service Safety, University of Science and Technology Beijing, Beijing, China; email: [email protected]
ABSTRACT The performance of waterproof bonding layer directly effects the durability of the highway bridge. Water permeability, shear strength and tension strength are three main indicators evaluating the waterproof bonding layer. In this research, three waterproof bonding materials including SBS modified asphalt, SBR modified asphalt emulsion and second order reaction waterproof material were selected. The water permeability, shear strength and pull-off strength were tested. The effect of different temperature and different contents were analyzed. Results show that: the water permeability resistance of waterproof bonding layer ranked as follows: SBS modified asphalt > Second order reaction waterproof material > SBR modified asphalt emulsion. Compared to SBR modified asphalt emulsion and Second order reaction waterproof material, SBS modified asphalt has a better shear resistance. Three waterproof *
- Corresponding author
materials used in this research all have temperature sensitivity. Their shear strength and tension strength decrease dramatically with temperature increasing. KEY WORDS Waterproof Bonding Layer, Highway Bridge, Water Permeability, Shear Performance, Pull-Off Performance
1. INTRODUCTION The performance of waterproof bonding layer in highway bridge directly influence the durability of the bridge structure. In recent years, how to choose the proper materials and design the waterproof bonding layer with excellent performance has attracted more and more attention. Existing studies show that the performance of waterproof bonding layer has a close relationship with the early distresses of bridge made of asphalt mixture. The damage of bridge paving has two types: one is the adhesion force between paving layer and bridge is too weak so that it’s easy for slippage or delaminating to happen between different layers. The other damage type is due to the weak water permeability of adhesion layer. The rain permeates through gaps and cracks into bridge, flushes the concrete, corrodes steel bar to decrease the service life of concrete bridge. So it is necessary to set a waterproof bonding layer to prevent these damages. In 1920, Danish first began to use concrete bridge deck waterproofing layer. With the development of highway and the study of researcher from various countries, bridge waterproofing bonding layer has been recognized around the world and attracted widespread attention. In 1970s, the waterproofing bonding layer was widely used in European and American countries. In July of 1972, fourteen countries from International Organization for Economic Cooperation and Development (OECD) jointly issued a research report on “concrete bridge deck waterproofing”. This report summarized each country's bridge deck waterproofing situation and the used methods, and systematically studied the bridge deck waterproofing membrane material used in each country. It also proposed a detailed specification about how to test the waterproofing bonding materials [1-5]. In 1976, United States Highway Cooperative Research Organization (National Cooperative Highway Research Program) published a bridge deck waterproofing report, which stated in detail the evaluation method of indoor waterproofing membrane performance. In 1995, based on the long-term testing and research of the concrete bridge deck waterproofing materials, a new construction, renovation, maintenance view point of bridge deck waterproofing system was proposed. In the early of 1950s, British TRRL (Transport and Road Research Laboratory) did a lot of research on bridge paving, especially for the water permeability, interlayer shear Performance of Waterproof Bonding Layer for Highway Bridge [6-9]. Guo et al. studied the interfacial adhesion property between asphalt binder and aggregate by conducting multiscale tests. They found the properties of materials and curing condition have a significant impact on the interfacial performance between asphalt binder and aggregate [10-16]. Though the interfacial behavior has been studied by multiscale test and numerical simulation, the real macro situation still has a distance to the theoretical model [17-18]. Some relevant tests are necessary to be conducted. In this research, the water permeability, shear performance and pull-off performance of three waterproof bonding materials are studied, and the effect factors are analyzed. 2. MATERIALS AND METHODS 2.1 Water Permeability The test device for water permeability used in this research was permeameter for structure layer material (Figure 1). This device consists of gas-pressure meter, fixed base, upper and lower clamping bolt and pressure plates with a pressurized cylinder. In order to prevent leaking, seal rings were used at the upper and lower pressurized plates, and bolts were used to
fasten the pressurized plates.
Figure 1. Permeameter for structure layer material The pressurized tube inner diameter of Material Permeability Tester was 100mm, the maximum water pressure is 0.7MPa. The specimen was "cement concrete + asphalt concrete" composite rolled using wheel tracking apparatus. The specification and number of mineral aggregates met the specification "Highway Engineering asphalt and asphalt testing procedures" (JTJ052-2000) in T0703-1993. Three different waterproof bonding materials between two layers were tested. The test methods and procedure were as follows: (1) Brush the waterproof bonding material on 30cm × 30cm sample surface twice to the optimum amount. Within 5 hours after first layer is completely dry, brush the second layer and treat the surface smooth by adjusting the brush force. Keep them at room temperature for 48 hours. (2) Put the waterproof bonding material into rutting sample mould with size 30cm×30cm×5cm. Use the rolling compaction method to mold the specimen, which consists of two layers “cement concrete + asphalt concrete”. One day later, demould it. (3) Placed the penetration instrument on a solid flat surface. Clean the specimen and put it in the middle of the base with the face of the waterproof layer upward. (4) Smear the butter around the pressing plate. Put the pressurized plate on the specimen and ensure the pressure plate and the base alignment. (5) Link the base and the pressing plate closely together by using the lower clamping bolt. (6) Use a bolt to link the pressurized plate and pressurized cylinder tightly. (7) Pour water into the pressurized cylinder until 2/3 volume. (8) Drop a few drops of red ink into the water, and then start the machine. Add air pressure into the pressurized cylinder to the regulations, and then keep them for 30 mins. (9) Observe the water permeability status of specimen, and record the time of water seepage. (10) When the test was done, open the pressurizes the valve to release the pressure to zero. Discharge the water in the pressurized cylinder, and then remove the specimen. Clean the machine for the further text.
2.2 Shear Performance The rut plate was used to mold test specimens. The cement concrete plate with size 30cm×30cm×5cm was obtained first, and then the surface was roughed, followed by seven days curing. Polish off the floating pulp on the surface of complete dried cement concrete, brush waterproofing bonding layer, and then pave asphalt concrete layer with thickness 5 cm. At last, wheel grinding instrument was used to mold the specimen. After 48 hours, the mould was released. Coring machine was used to get a 100mm × 100mm double layer specimen. Structure material electric shear apparatus was used to study the shear performance. The study program is shown in Table 1. The effects of waterproof materials type, test condition and material contents on shear strength resistance are mainly studied.
Effects Temperature Materials types Materials content
Table 1. The program for shear performance tests Levels 25℃、40℃、60℃ SBS modified asphalt、SBR modified asphalt emulsion、Second order reaction waterproof material 2 0.6 kg/m 、,1.0 kg/m2、1.5 kg/m2、2.0 kg/m2
2.3 Pull-Off Performance The pull-off test sample size is similar with the shear test samples. The molding method is same with that in section 2.2. The structure materials strength tester was used to study the tension performance in this research. The surface of two specimens should be clean before testing, and then epoxy resin was used to adhere the specimen and mold together. Keep them at room temperature for 24 hours until the epoxy resin solidified completely. In this research, the tension rate was set as 20 mm/min. Two temperatures 25 oC and 60 oC were selected and three different waterproofing bonding materials were studied. 3. RESULTS AND DISCUSSION 3.1 Water Permeability The water permeability resistance of waterproof bonding layer was shown in Table 2. It can be seen from Table 2 that the water permeability resistance of waterproof bonding layer tested in this research ranked as follows: SBS modified asphalt > Second order reaction waterproof material > SBR modified asphalt emulsion. For the waterproof bonding layer of the highway bridge, a good performance should be able to resist water leaking after paving the asphalt mixture and road roller rolling. However, it’s easy for the moisture damage to happen in the asphalt pavement due to the raining, traffic, and other environment effects. When the adhesion between asphalt binder and mineral aggregate is weak, or the void content
is high, or the compaction degree is small, the moisture damage will become worse. The moisture damage can further lead to potholes, slurry pump etc. So the function of waterproof bonding layer is to prevent the outsider water leaking into the inside of the bridge concrete to avoid the moisture damage.
Water pressure （MPa）
Table 2. Test results of water permeability resistant. Waterproof bonding layer Water seepage situation
0.1
SBR modified asphalt emulsion
No water seepage within 30 mins
0.1
SBS modified asphalt 0.3
No water seepage within 30 mins
0.1 0.2 0.2 0.2 0.3
Second order reaction waterproof material SBR modified asphalt emulsion
No water seepage within 30 mins No water seepage within 30 mins
SBS modified asphalt 0.3
No water seepage within 30 mins
Second order reaction waterproof material SBR modified asphalt emulsion
0.3
SBS modified asphalt 0.3
0.3
Second order reaction waterproof material
No water seepage within 30 mins Water started to leak at 10 mins, and leak became worse at 20 mins. No water seepage within 30 mins Water started to leak at 25 mins, and leak became worse at 35 mins.
3.2 Shear Performance The shear stress can be calculated in Equation (1). τ
F S
(1)
Where, τ——shear stress (MPa); F——shear force (N); S——Shear area (m2). (1) Effect of waterproof bonding layer content on the shear performance of interlayer The contents of waterproof bonding layer were selected as 0.6kg/m2，1.0kg/m2，1.5kg/m2， 2.0kg/m2. The test results are shown in Figure 2.
Shear strength τ (MPa)
0.6 0.5 0.4 0.3 SBS modified asphalt SBR modified asphalt emulsion Second order reactio waterproof material
0.2 0.1 0 0
0.5 1 1.5 2 Content of waterproof bonding layer (kg/m2)
2.5
Figure 2. Shear strength of waterproof bonding layer with different materials. It can be seen from Figure 2 that with the increasing of the waterproof bonding material content, the shear strength increases first, and then decreases. Based on the tested data, we can obtain the fitting equation of shear resistant strength for SBS modified asphalt as follows: τ＝-0.097X2+0.31X+0.30 R2＝0.89 Where, τ —— the shear resistant strength (MPa). X ——the content of waterproof bonding material (kg/m2).
(2)
When X=1.50, the shear strength reached maximum. Similarly, the fitting equation of shear resistant strength for second order reaction waterproof material can be shown in Equation (3). τ＝-0.19X2+0.54X+0.10
R2＝0.90
(3)
When X=1.40, the shear strength of second order reaction waterproof material bonding layer reached maximum. The fitting equation of shear resistant strength for SBR modified asphalt emulsion waterproof material can be shown in Equation (4). τ＝-0.01X2＋0.04X+0.36
R2＝0.93
(4)
When X=1.61, the shear strength of SBR modified asphalt emulsion waterproof material bonding layer reached maximum. It can be seen from Figure 2 that when the content of waterproof bonding material is little, the waterproof bonding layer would form a discontinuous thin film, which decreases the shear strength. When the content of waterproof bonding material is too much, the
frictional resistance between different layers is decreased. Therefore, there should be an optimum content of water proof bonding materials to balance the interlayer adhesion and interlayer friction. (2) Effect of test temperature on shear strength of waterproof bonding layer In this research, three test temperatures were seltected: 25 oC, 40 oC and 60 oC. The optimum contents of waterproof bonding materials were applied to study the shear strength. The tests results are shown in Figure 3. 0.6 Shear strength τ (MPa)
0.5
25℃
40℃
60℃
0.4 0.3 0.2 0.1 0 SBS modified asphalt
SBR modified asphalt emulsion
Second order reaction waterproof material
Figure 3. The shear strength of waterproof bonding materials at different temperatures. It can be seen from Figure 3 that the shear performance of waterproof bonding material depends on the temperature significantly. With the temperature increases, the shear strength of three waterproof bonding materials decreases dramatically. When the temperature rose from 25 oC to 40 oC, the shear strength decreased by around 80%. With the temperature further increased to 60 oC, the shear strength dropped to 10% of that at 25 oC. The shear resistance of SBR modified asphalt emulsion has the most temperature sensitivity, followed by second order reaction waterproof material. The SBS modified asphalt has the least temperature sensitivity. 3.3 Pull-Off Performance The tension stress can be calculated as Equation (5). P=
F S
Where, P—Adhesion strength（MPa）； F—Tension force（N）； S—Area of fracture surface（mm2）。 Test results are shown in Figure 4.
(5)
0.6
No waterproof bonding layer
Shear strength τ (MPa)
0.5
SBS modified asphalt SBR modified asphalt emulsion
0.4
Second order reaction waterproof material 0.3
0.2
0.1
0 25
60 Temperature（℃）
Figure 4. The adhesion strength of different materials at different temperatures. It can be seen from Figure 4 that at 25 oC, the adhesion performance of three waterproof bonding materials ranks as follows: SBS modified asphalt > Second order reaction waterproof material > SBR modified asphalt emulsion > No waterproof bonding layer. SBS modified asphalt has a good temperature sensitivity. If the content of SBS modified asphalt is proper, it will form an adhesion layer with good tension performance on the surface of cement concrete. The asphalt based waterproof bonding materials all have temperature sensitivity. With the temperature increasing, not only the shear performance decreases dramatically, but also the tension adhesion performance declines significantly. It can be seen from Figure 4 that the tension strength at 60 oC was much lower than that at 25 oC. At 60 oC, the tension strength were all more than 0.4 MPa, but when the temperature rose to 60 oC, it decreased to 0.1 MPa, which is only 3%~20% of that at 25 oC. 4. SUMMARY OF FINDINGS In this research, three waterproof bonding materials were studied. The water permeability resistance, shear strength resistance and tension strength resistance were investigated. And the effect factors were analyzed. The followings are the other main findings from this study: (1) Compared to SBR modified asphalt emulsion and Second order reaction waterproof material, SBS modified asphalt has a better water permeability resistance. (2) The shear resistance of three waterproof materials ranks as follows: SBS modified asphalt > Second order reaction waterproof material > SBR modified asphalt emulsion. (3) Three waterproof materials used in this research are all temperature dependent. Their shear strength and tension strength decrease significantly with temperature increasing.
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