THE BRIDGE DECK PAVEMENT WATERPROOFING  

 

There is settled tendency of increase of the aggressive environmental activity on the bridge structures and it reduces the longevity of bridges.

   

 

The development of effective compounds and technologies of thin waterproof layers resistant to the aggressive environmental activity, to the transport impact, to the thermal cracks formation will extend the life time of frameworks of bridges.    

 

Currently on the roads of Belarus more than 4000 bridges with total length of 140 km. The durability mostly depends on the quality and reliability of waterproofing. Every year the aggressive environment activity is influenced on the bridges longevity. The mean reasons of the damage of bridge pavement structure waterproofing are the mechanical failure of the bitumen protective layers of the floor under the influence of thermal strains and transport activity (Figure 1). It leads to the formation of micro cracks in protective waterproof layers, in which the water and there is the aggravating damaging effect of thermal strains.

 

 

 

       

 

Figure 1. The damaged asphalt pavement of bridge roadway.

1

The traditional technologies of waterproofing repair are expensive and often no effective. For repair of roll waterproofing it is necessary to disassemble all overlying layers of asphalt and cement concrete protective layer (Figures 2,3). These works require significant timetable and as a rule to increase the time of work, reduce the quality of repair and to create the fault conditions for transport and brides maintenance.  

     

 

Figure 2. The dismantling of pavement of bridge floor.

     

 

 

 

Figure 3. The view of the roadway of the bridge structure after removal of the protective layer. 2

The native and foreign experience proved that the roll waterproofing (Figure 4) are not provided the isolation longevity of roadway. The life time about 5 years and it less than projected service life of bridge. Lack of life also can be in the force of low quality of handwork under the laying.  

     

     

Figure 4. The roll waterproofing of the bridge roadway.

 

 

 

The development of the effective compounds and technologies of thin protective waterproof layers effective against the aggressive environmental activity, transport activity and the fracturing allows to prolong life time of bridges. The new composition of vibromastic asphalt with bitumen polymer agent for road bridge surfacing was developed in BeldorNII as waterproof and as the basic coating. According this technology fully or partly the upper protective asphalt layer is removed depending on the state. The dismantling or substitution of roll waterproof no necessary. After completing the preparatory works the waterproofing layer from vibromastic asphalt is paved. These works not been requested the special equipment (mobile boiler, special pavers for mastic mixtures). Vibromastic asphalt mixtures have been transported by normal asphalt pavers. For the strength guarantee and shear stability the composition of vibromastic asphalt including 50-65% of macadam. The waterproofing and deformation behaviors of vibromastic asphalt are provided till 8% of modified bitumen. As a modifiers of bitumen the thermoplastic elastomers of SBS type, rubber crumb, EVA additives and so on can be used.

3

The modifying rubber containing additives as can be added directly into mixer. So no sense to have expensive equipment for preparing of modified bitumen. The requirements for quality characteristics of the vibromastic asphalt and physical-mechanical properties of asphalt with have been done in the Table.  

 

The physical and mechanical properties of vibromastic asphalt with additives

 

   

The name of characteristics

 

%

Requirements of  

1

2

STB 2074-2010

the porosity of mineral frame, % in the volume

13

14

10 - 15

Residual porosity, % in the volume , no more

0,4

0,6

1,0

0,3

0,4

0,5

1,6

2,1

1,5

2,5

2,7

1,5 – 3,0

0,93

0,94

0,90

1,2

0,8

1,5

2,44

2,40

2,0

 

 

water saturation, % in the volume, no more ultimate compression strength, mpa  

under the temperature 50 °С , no less tensile strength, mpa under the temperature 0 °С  

coefficient of water resistance under long-term water saturation in aggressive sphere in 14 days, no less indentation depth under 40 ºС, mm, no more Shear strength, mPa under the temperature 50 °С, no less

  In consideration of many factors influencing on the durability of the protective layers of bridges (thermal behaviors, transport activity, character of vehicles movement, thermal and dynamic deformations of framework of bridge) the design of the structure and composition of materials for protective layers must be individualized. The developed method of asphalt mixture design in BeldorNII is allowed to determinate the optimum composition of the vibromastic asphalt for each climate zone, road category and bridge construction. Under the 0,3 m p a testing after 30 min. in water storage the sample must be keeping the property of impermeability to water. The absolute impermeability to water of vibromastic asphalt is provided with high % of binder and low porosity (less 1,0%).

 

4

The very important moment is the prevention of a plastic deformations of the protective layer under transport impact in high temperatures. Often the wheel tracking is the reason of asphalt pavements failure. The figures 5 and 6 are the test setup and the samples after determining the stability to wheel tracking.  

 

 

 

Figure 5. The test setup with repeated loading

 

 

 

 

 

Figure 6. The asphalt sample after determining the stability to wheel tracking. 5

The test setup allows to test asphalt under +30…+60 °С providing the wheel load on the sample from 0,5 - 0,8 МPа. Test modes and the number of loading cycles are assigned according the climatic zone and the predictable traffic volume on bridges. The resistance to wheel tracking is provided with introduction in asphalt the various modifiers. The type and the amount of modifying agent depending on bridges external environment. The stability of vibromastic asphalt to cracks formation under the low temperatures is characterized with the stiffness modulus determined on the device (Figure 7).    

 

 

Figure 7. The device for determination of asphalt stiffness modulus.

 

 

 

The stiffness modulus of vibromastic asphalt is regulated at the stage of mixture design. During recent years the technology of laying a bridge deck pavement from vibromastic asphalts was approved on the Roads of Belarus and Russia. The vibromastic asphalt was prepared on the batch operation plants. The combined rubber-containing modifier was fed into mixer through the feed line of stabilizing additives. The temperature of ready mixture was 190-210 0С The layer thickness was 4-5 cm in the process of asphalt laying (Figure 8).

6

 

Figure 8 Laying the vibromastic asphalt by asphalt paver.  

 

The distinctive feature of asphalt paving of the vibromastic asphalt is absence of special measures for compacting. The pavements of bridges built according this technology have increased resistance to the transport impact, the deformation under low temperatures, the crack formation and provide reliable water resistance.

 

 

CONCLUSION  

 

 

An application of the vibromastic asphalt allows to increase the interrepair time of pavements not carrying the works of replacement of the existing waterproofing. It significantly reduces material cost. The application of complex modifiers ( ) in preparation of vibromastic asphalts simplifies the technology not requiring the special equipment for bitumen modification and the transportation of mixture, not requiring to switch over of plants and not changing the technological behaviors of preparing and laying mixtures.

7