Combined with the example of steel bridge deck pavement engineering of Jiangshun Bridge, how to improve the structural depth and anti-skid performance of the upper layer of steel bridge deck pavement were studied. The conventional epoxy asphalt mixture mix was optimized, and the performance of the optimized graded epoxy asphalt concrete was verified by laboratory test and test road pavement analysis. The results show that the performance of the optimized coarse graded epoxy asphalt mixture is similar to that of the conventional dense graded mixture, and the surface structure and anti-skid performance are significantly improved.
Keywords:
Steel bridge deck pavement |Construction Depth |Fatigue Durability |Mix ratio |Asphalt-rich mixture FAC-10
As an important part of bridge driving, the main function of bridge deck pavement material is to provide long-term stable and smooth driving road surface for driving vehicles, and the quality of bridge deck pavement directly affects the safety, comfort, durability and investment benefits of driving. Due to its special use conditions, orthotropic steel bridge decks require the pavement layer to have good deformation ability, good high temperature stability, long service life and fatigue cracking resistance [1]. Epoxy asphalt concrete has superior mechanical properties, high strength, good follow-up, excellent high temperature stability and fatigue resistance, strong interlayer bonding, and can meet the special requirements of steel bridge deck.
Epoxy asphalt concrete as a steel bridge deck pavement material, its mix ratio mostly adopts a finer suspension dense structure, this type of structural mixture has a high compactness and cohesion, but the internal friction angle is small, easy to cause the problem of insufficient anti-slip force in wet state. In order to improve the anti-skid performance of steel bridge deck pavement without reducing its road performance, this paper optimizes the design of epoxy asphalt concrete gradation based on the actual engineering example of steel bridge deck pavement of Jiangshun Bridge, and analyzes and compares the performance of the optimized gradation with the conventional gradation, so as to provide a basis and reference for the further promotion of epoxy asphalt mixture in China.
1. Project overview
Jiangshun Bridge is a bridge across the Xijiang River in the Guangfojiang River Expressway, the total length of the steel box girder is 1020m, the total width of the bridge deck is 39m, and the main span is 700m. The main bridge is a cable-stayed bridge with twin towers and double cable-faced steel-concrete mixed beams, and the main girder is a streamlined flat box girder. The bridge deck of the steel box girder adopts an orthotropic plate structure, and according to the force needs, the roof adopts a thickness of 20mm near the tower and the steel-concrete joint section, the thickness of the roof in the fast lane of other areas is 16mm, and the thickness of the roof in the range of the heavy lane is 18mm. The average monthly maximum temperature in Guangdong reached 284. The highest temperature in summer is 387, the lowest average temperature in history -3, the design temperature range of bridge deck pavement materials -5 65. The steel bridge deck pavement structure of Jiangshun Bridge is shown in Figure 1.
2. EA-10 mix ratio optimization design
2.1. Design ideas.
To improve the anti-skid performance of asphalt concrete pavement, the main reasons are: (1) selecting appropriate anti-skid layer materials and appropriately increasing the macroscopic structural depth; (2) Adjust the aggregate gradation so that the particle size is 4The coarse aggregate content of 75mm is more to obtain a relatively ideal anti-slip performance index; (3) Rubber powder is used to modify the asphalt mixture to improve the surface texture [2-3].
For the epoxy asphalt mixture for steel bridge deck pavement, in order to improve the surface structure depth and anti-skid performance, this paper mainly adjusts the gradation. The coarser gradation can prolong the fatigue life of the pavement layer, but reduce the anti-skid ability of the pavement in wet conditions, and fatigue resistance and anti-skid are a contradiction when choosing gradation [4]. The design ideas are as follows: (1) Starting from the coarser gradation, the construction depth is improved, and the gradation design of FAC-10 is referenced. (2) In the design of the upper layer mixture, the same 0% 3% porosity control is used with the lower layer, and the performance of the mixture is checked by the strength and deformation performance of the mixture, so as to ensure the durability and fatigue resistance of the pavement layer mixture. (3) The performance test data of the optimized mixture were compared with the performance of the conventional densely graded EA-10 epoxy asphalt mixture.
The design of Fullasphaltcontent (FAC) is based on the interference theory, and the method of volumetric design is used to design the mixture [5], so that the coarse aggregate forms a skeleton embedded extrusion structure, and the fine aggregate and asphalt mortar fill the voids of the skeleton [6]. The mixture designed according to the FAC method not only ensures the full embedding and extrusion of the skeleton, but also controls the void, so that the performance of the mixture is improved.
Specific engineering practice, Guangdong Mafang Bridge in 2011 using FAC-10 epoxy asphalt mixture for a single layer 75mm pavement test section, after 3 years of heavy traffic, thin steel plate conditions of operation inspection, is currently running well, Mafang Bridge plans to use the scheme in 2015 for 9-span overhaul.
2.2. Design gradation.
2.2.1 aggregate.
The aggregate must be hard, dense, clean, wear-resistant, with good particle shape (similar to a cube), no weathering surface, and hard stone with good bonding properties with the binder. Coarse aggregates are made with particle sizes greater than 236mm high-quality crushed stone aggregates such as basalt, diabase, diorite, etc., with a particle shape similar to a cube. This project uses diabase from Heyuan or Guangxi, and its technical indicators are shown in Table 1 and Table 2.
2.2.2. Epoxy asphalt.
Japanese hot-mix epoxy asphalt binder is adopted, which is composed of matrix asphalt, epoxy resin main agent and curing agent. The mixture formed by mixing the main agent and the curing agent according to 56 44 is mixed with asphalt in the ratio of 50 50, and is cured and formed under a certain temperature to form epoxy asphalt. The asphalt used when the epoxy resin main agent is mixed with asphalt is A-70 base asphalt. The technical indicators of epoxy resin and epoxy asphalt after mixing are shown in Table 3 and Table 4.
2.2.3-level design.
The three typical structural forms of asphalt mixture are: suspended compact structure, skeleton void structure, and skeleton compact structure. In order to avoid cracking, loosening, potholes and other diseases in the bridge deck pavement, a dense structure should be selected. Epoxy asphalt is a thermosetting material, which becomes soft but not flowing at high temperature, so the suspended dense epoxy asphalt mixture theoretically has good high temperature stability, and the gradation design should ensure that the mixture has excellent fatigue resistance. Referring to the asphalt pavement specification AC-10 suspension compacting gradation range, according to the upper and lower limits of the design gradation, the conventional epoxy asphalt mixture dense gradation is called EA-10. Drawing on the FAC-10 skeleton compact structure of the steel deck pavement of the Mafang Bridge in the actual project, on the basis of the conventional dense gradation EA-10, it is continuously adjusted475mm、2.36mm、1.The pass rate of 18mm and other sieve holes makes it finer than the FAC-10 gradation, and the optimized gradation is recorded as EA-10. During gradation adjustment, the void ratio of 0% and 3% is always controlled. The design gradation is shown in Table 5.
3. Performance inspection of epoxy asphalt mixture
3.1. Low temperature trabecular flexure test.
According to the test procedure (JTGE20-2011T0715), the epoxy asphalt mixture with the optimal amount of asphalt was evaluated by the low-temperature trabecular bending test, and the test results are shown in Table 6. The results of low-temperature trabecular flexure test show that the flexural tensile strain of conventional dense EA-10 is 321e 03, the flexural tensile strain of the upper layer after the optimized gradation is 315e-03, lower layer 309e-03, all greater than 30e-03 to meet the design requirements.
3.2. Water stability test.
The best oil-stone ratio of 6The Marshall test was carried out according to the JTGE20-2011T0709-2011 procedure, and the test results are shown in Table 7. The results of water stability test showed that the residual stability of conventional dense EA-10 was 9802%, the residual stability of the upper and lower layers of the specimen after optimized gradation is. 5%, all of which meet the requirements of Marshall residual stability greater than 85% in the design inspection index of mixture mix.
3.3. High temperature stability test.
Use the optimal amount of asphalt 65% rutting specimens were prepared, and epoxy asphalt mixture rutting test was carried out in accordance with JTGE20-2011T0719-2011 regulations, and the test temperature was 70, and the test results are shown in Table 8. The results of the high-temperature stability test show that the rutting stability of the conventional dense graded EA-10 is 13547 times, and the residual stability is 11472 times mm and 11911 times of the upper and lower layers of the optimized graded specimen, which meets the requirements of the dynamic stability of the rutting test of the mix ratio design test is not less than 8000 times.
4. Test road paving
On November 29, 2014, about 100m long and 14The 5m wide steel box girder was paved with epoxy asphalt concrete test section, and the optimized gradation was used as the target mix ratio. On December 5, the test road was tested, and the test items included structural depth, friction coefficient, and the thickness, gradation and interlayer bonding were observed, and the average test results are listed in Table 9.
As can be seen from Table 9, the structural depth of the upper layer of EA-10 optimized epoxy asphalt mixture after gradation optimization is 055, the anti-slip coefficient is 61, all can meet the design requirements. The EA-10 before optimization has a construction depth of 042, the anti-slip coefficient is 48, all of which do not meet the design requirements. The water permeability coefficient and interlayer bonding can meet the requirements. Therefore, the surface structural depth and anti-slip coefficient of epoxy asphalt mixture after gradation optimization have been improved.
5. Conclusion
In this paper, in order to improve the structural depth and anti-skid performance of the surface layer of the steel bridge deck pavement, the EA-10 mix ratio of epoxy asphalt concrete was optimized based on the Guangdong Jiangshun Bridge Project, and the low-temperature bending performance, water stability, high-temperature stability and anti-skid performance of the pavement were analyzed and compared with the conventional graded mixture. The results show that:
1) Combined with the actual engineering examples, referring to the AC-10 type gradation of the asphalt pavement specification, the EA-10 gradation is optimized by using a finer gradation than FAC-10, which can effectively improve the anti-skid performance of the epoxy asphalt mixture.
2) In the design of the upper layer mixture, the same 0% 3% porosity control is used with the lower layer, and the optimized coarser gradation of epoxy asphalt concrete EA-10 is preferred, and its low-temperature trabecular bending test, water stability test and high-temperature stability test can meet the design requirements.
3) Referring to the application effect and test performance test of the engineering test section, it shows that the performance of the optimized coarse graded epoxy asphalt mixture is similar to that of the conventional dense graded mixture, and the surface structure and anti-skid performance are significantly improved, which is basically feasible as the upper layer of Jiangshun Bridge pavement.
End of full text. It was first published in Guangdong Highway Traffic, No. 6, 2015. About author:YUAN Ling (1987-), female, from Huangmei, Hubei Province, master of engineering, main research direction: subgrade pavement design and theoretical research.
The DTS-30 CTS-30 Multifunctional Pavement Material Dynamic Test System is a hydraulic servo testing system that uses digitally controlled high-performance servo valves and provides accurate loading waveforms at frequencies up to 100Hz. The DTS-30 CTS-30 versatile pavement material dynamic testing system can perform tensile, compression, and dynamic loading, and is suitable for testing a wide range of different materials such as asphalt, soil, unbonded scraps, fibers, and plastics. The DTS-30 CTS-30 is equipped with the Italian Matest-P**Etest CDAS CDAS2 digital controller, TestLab2 software and a full set of test accessories, realizing a good combination of hardware and software. The DTS-30 CTS-30 Dynamic Test System is a compact, fully integrated, user- and environmentally-friendly test system.
Features:
Compact, sturdy loading rack.
Small footprint: 90cmx135cm, including hydraulic power unit and environmental chamber.
The reaction frame is embedded in the environmental cabinet.
Movable temperature control unit.
The full set of configurations is suitable for a wide range of test applications.
Digital hydraulic servo control.
The standard configuration is 4-axis control and a 16-channel data acquisition system (with optional high-end CDAS CDAS2).
For more knowledge and equipment related to road traffic, civil engineering and geotechnical, please contact tiptop!