Sealing of cold technological joints of asphalt concrete coatings as a necessary element of increasing the repair time.
The topic of increasing the time between repairs of asphalt concrete pavements has been exciting minds for as long as the topic of asphalt concrete pavements itself exists. It has already been huge amount of discussions and will be even more about which types of asphalt concrete mixtures are better, which way it is better to compact it, which method to use when designing, etc. But any coating made using any technology has vulnerabilities, these are the places where the coating adjoins each other, to the curb stone, drainage trays, rails, etc. There is no doubt that the coating closest to the ideal is the one, which is installed, roughly speaking, “in one go”, that is, when the work of the asphalt concrete mixing plant and the concrete laying division is so well managed that there are no interruptions in the supply of ACM, the entire section of brickwork is covered with with the help of asphalt spreaders and the process continues without any breaks for lunch, sleep and a smoke break, we get a coating without cold technological joints. But even such a coating can be interfaced with drainage trays, curbs, and other structures, and at these joints the compaction of mixtures is always lower than on the main coating. In other words, the penetration of moisture and the beginning of destruction cannot be avoided in the future. We should also consider that in 98% of cases of reconstruction of the AC pavement, it is impossible to completely overlap the road and you have to lay the ACM in two or more stages and we get a cold technological joint directly between the layers of the AC pavement which has all the same problems as in case of junctions of the ACM to concrete and metal structures. They include reduced density, increased water saturation, non-tight joint, depleted in binding material.
There are many ways to improve the situation with the preparation of a cold joint:
Infrared heaters;
Bitumen emulsion;
Spillage of the joint with bitumen;
But they all have one drawback in comparance to the tapes, this is an unstable filling of the joint with a cementing material, and infrared heating heats the joint, but does not fill it with a cementing material, the joint remains depleted.
According to available data, each of the above methods fills the joint in its own way:
Infrared heating – 0 g/lm
Emulsion – 12-17 g/lm
Bitumen spillage – 30-50 g/lm (very unstable)
Bitumen polymer tapes:
Thickness 5 mm. – 230 g/lm
Thickness 8 mm. – 390 g/lm
The filling capacity of the joint using tape is much better, the joint is completely sealed with a tape composition and protected from moisture penetration.
The composition of the tape is made of a mixture of bitumen with a polymer with an increased concentration of polymer, which provides additional mechanical strength of the joint and its complete sealing. That is, at the junction of the asphalt layers, a highly saturated polymer bitumen binder is obtained, which additionally increases the mechanical strength of the joint. The same effect is observed at the joints with concrete and metal structures.
One of the advantages of using sealing tapes with a high polymer content is the ability to perform the functions of a shock-absorbing cushion that dampens vibration at the asphalt-rail junction, which does not destroy the asphalt with vibration, but this function of the tape is fully revealed only on tapes with a thickness of at least 8 mm. German experience shows that at such junctions it is necessary to use at least 10 mm. Tapes for complete dampening of rail vibration.
The sealing tape must contain an increased amount of polymer in its composition, if this is not the case, then the melt of the tape does not give the effect of fixing the joint. The increased polymer content allows the tape to keep its shape at elevated ambient temperatures, which simplifies its installation on hot days. The increased polymer content compensates for the increased plasticizer content, which gives improved performance at low temperatures. The approximate content of the polymer in the tape can be determined due to the ring-and-ball softening point, this parameter should not be lower than 850C, while the Fraas brittle point should be in the range of minus 25 – 300C. That is, the plastic range of the tape must be at least 1000C.
For convenience of fixing of a tape to vertical surfaces, curb stone, trays or rails, the Germetex company provided the tape with an adhesive layer that allows, without additional equipment (for example a burner), to fasten a tape to a surface.
The burner can also be used at low ambient temperatures, in this case, you can use a tape without an adhesive layer.
Germetex Company produces the main, proven standard sizes of bitumen polymer sealing tapes 50×5 and 50×8, their versions with an adhesive layer. Moreover, at the request of the customer we can make tapes especially for roof profiled sheets, under the condition of use of thin layers of wear with a layer thickness less than 5 cm that will allow more rational use of money of contractors.