epoxy asphalt concrete paving on the deck of long-span steel bridges

1、REPORTS Chinese Science Bulletin Vol. 48 No. 21 November 2003 2391Chinese Science Bulletin 2003 Vol. 48 No. 21 2391?2394Epoxy asphalt concrete paving on the deck of long-span steel bridgesHUANG Wei, QIAN Zhendong,

2、 CHEN Gang (2) mas- tic asphalt project, typically in England; (3) stone mastic asphalt (SMA), a kind of modified asphalt lately used in Germany and Japan; and (4) epoxy asphalt, mostly adopted in USA. Epoxy asphalt

3、concrete is a kind of high- strength and flexible material by adding thermosetting epoxide resin and solidified agent into asphalt[1]. As a paving material, epoxy asphalt is mainly applied for steel bridge deck in US

4、A, Canada and Australia, especially in USA. But this material has never been used for paving bridge deck in China until its application in the SNYRB. These years, the construction of long-span bridges in China has de

5、veloped very fast. Many paving techniques of Japan and England have been adopted in constructing bridges. However, these techniques are not completely applicable for the particular climate and traffic conditions in C

6、hina. Furthermore, the steel girder box structure, once universally used by foreign countries, has been applied in long-span bridges recently constructed in China, and the highest temperature of the paving of bridge de

7、ck in most areas of China can reach 70?. So the paving material must possess the higher temperature stability. The paving layer of many bridges was damaged shortly after being put into use. In fact, the paving techni

8、que of steel bridge deck depends to a large extent on the structure of steel bridge deck and natural environment. Deep and systematic re- search on paving of steel bridge deck is very limited in China. In this paper,

9、the composition design of epoxy as- phalt concrete, its characteristics and service performance of the mixture, bond performance of epoxy asphalt con- crete with steel plate, the fatigue test of complex girder formed b

10、y the steel plate and epoxy asphalt concrete, are firstly and systematically studied. In addition, epoxy as- phalt concrete is successfully applied in the paving of steel bridge deck of the SNYRB, and the paving layer

11、of the bridge has shown an excellent performance after it has been put in use for more than one year. 1 Epoxy asphalt concrete as paving material (?) Epoxy asphalt. According to different pur- poses, epoxy asphalt ca

12、n be classified into two types: ma- terial for bonding layer (type Id) and for binder (type ?). Commonly, epoxy asphalt is made out of two components: component A (epoxy resin) and component B (homoge- neous complex co

13、mposed by petroleum asphalt and so- lidified agent). If the two components have bad compati- bility, medium should be added. (?) Aggregate. Requirements of epoxy asphalt concrete for aggregate are rather strict. Aggre

14、gate should be clean, rigid, wear proof and non-acid minerals with 100% broken surface. Its favorite shape should be a cube. Light color is better to reduce the heat caused by solar radiation in high-temperature seas

15、ons. Limestone flour is used as filling mineral and contains at least 90% limestone, but none active lime should be used. From the experience of key projects and general consideration of all kinds of test index (most

16、 tests are Los Angeles abrasion tests), ba- salt from the Huashang Mountain in Jurong is chosen as the aggregate for the SNYRB. The results for all charac- teristic tests are as follows: Los Angeles abrasion loss is 10

17、.6% (after 500 rotation cycles), the crash value is 8.6%, the polishing value (psv) is 52, water-absorbing capacity is 1.0%, compression strength is 138 MPa, binding power is 4-level, sand equivalent is 50 and the sle

18、nder and flat particles form a proportion less than 2.65%. (?) Gradation design for aggregate. The fatigue life-span of the paving layer could be extended by using fine graded aggregate. However, macroscopic roughne

19、ss would be reduced accordingly and so would the sliding strength of pavement under moist conditions. After a lot of comparison with the test results, gradation and the forbid- den zone of Superpave’s aggregate gradat

20、ion are shown in Fig. 1. REPORTS Chinese Science Bulletin Vol. 48 No. 21 November 2003 2393Table 2 Bending test for different kinds of asphalt mixture (at 15?)Material Damage strength/MPa Maximum strain Bending

21、 stiffness modulus/MPa AC modified asphalt mixture 5.95 1.056?10?2 563SMA 4.73 1.325?10?2 355Epoxy asphalt mixture 16.4 6.372?10?3 2574deformation degree (deflection at the span center) of the epoxy asphalt concre

22、te is smaller than that of the other two materials. In addition, at 20? the compression inten- sity is 40 MPa using the uniaxial compression test. (?) Deformability and low temperature properties of epoxy asphalt conc

23、rete. Low temperature properties and the deformability of the epoxy asphalt concrete asphalt mixture are tested by bending and splitting tests at low temperature. Results of the splitting test at low tempera- ture ar

24、e shown in Table 3. Contrasted with SMA and AC modified asphalt mixture, epoxy asphalt mixture performs better at the low temperature. With the decrement of the temperatures, the maximum strain of SMA and AC modi- fie

25、d asphalt mixtures fell to a greater extent than that of epoxy asphalt (contrasted with the test result at 15?). (?) High temperature property and water stability of epoxy asphalt concrete. At 60? and 70?, the dynamic

26、 stability of the AC modified asphalt mixture is 2193 and 695 (times/mm) and that of SMA is 2562 and 694 (times/mm), respectively. For epoxy asphalt concrete, the deformation at 60? is almost 0 and the dynamic stabil

27、ity 5460 (times/ mm) at 70?. Therefore, both the dynamic stability and the temperature property of epoxy asphalt are much better than those of other two kinds of asphalt mix- ture. At the same time, epoxy asphalt conc

28、rete shows su- per water stability in the soaking Marshall test. Therefore, epoxy asphalt concrete has a better resistance against water damage. (?) Lineal shrinkability of epoxy asphalt concrete. If the thermal shrin

29、kage coefficient of paving layer dif- fers too much from that of the steel plate, cracking and slipping may take place under the temperature stress. Be- cause shrinkage often fails in the low-temperature area, the temp

30、erature for our experiment is set between ?15? and 5? when the lineal shrinkage coefficient of epoxy asphalt concrete is between (1.3—2.5?10?5)??1 and (1.1—1.4?10?5)??1 for the steel plate. The difference of the shrin

31、kage coefficient for the paving layer and the steal plate is not too large and almost remains 0 especially at low temperature. (?) Fatigue resistance of epoxy asphalt concrete. Researches on indirect tension (splitti

32、ng) methods in re- cent years demonstrated that the indirect tension test can be used to describe the fatigue characteristics of the as- phalt mixture[2]. Splitting tests on the epoxy asphalt mix- ture, SMA, Gussasphal

33、t concrete mixture and high grade modified asphalt concrete showed that the fatigue resis- tance performance of epoxy asphalt is the best. 4 Fatigue performance of epoxy asphalt concrete paving on steel bridge deck F

34、atigue performance of epoxy asphalt concrete pav- ing of steel bridge deck can be more accurately reflected when paving layer and the steel plate are considered as a total subject investigated. According to the calcula

35、tion results of the finite element analysis, maximal tensile stress and tension strain of the paving layer occur on the top of U type rib stiffener (Fig. 2, point A) under traffic load, with their directions vertical

36、 to driving course. Tak- ing point A as the center of a circle, the beam with 300 mm span and 100 mm width is intercepted on the bridge deck. Load and support are shown in Fig. 2. The loading force in the fatigue test

37、 can be equiva- lently converted based on stress, namely, the maximal tensile stress on the paving layer of complex beam is equal to that on paving layer of the bridge. When the load force of the fatigue test was 5 kN

38、, beam loading wave was sine, and the loading frequency was 10 Hz[3,4] , the com- plex beam 2 showed no damage at room temperature of 18? over circulatory load with 5 kN, the maximal value for 12000000 times, indicat

39、ing that the designed epoxy asphalt concrete paving system can meet the traffic and load requirements for 15 years at room temperature. To further test the overload resistant property of the bridge deck, complex beam

40、 4 was utilized. It was still not damaged at room temperature of 18? when the loading force was increased to 6 kN (the minimal value was still 0.5 kN) and the load with a 6 kN kept circulatory and constant for 120000

41、00 times. Complex beam 5 cracks in the middle of the span after having been loaded circularly with a maximal value of 12 kN and minimal value of 0.5 kN for 85000 times. Complex beam 6 cracked in the mid- dle of the

42、span after a circulatory load with maximal value Table 3 Bending test s for different kinds of asphalt mixture (?15?)Material damage strength/MPa Maximum strain (10?6) Bending stiffness modulus/MPa AC modified asphal