The invention relates to a method for sealing the joint between two road parts which are movable relative to each other and are provided with, or are to be provided with an asphalt road surface, in particular the joint between two bridge roadway parts or between a bridge roadway part and a land-abutment part, comprising:
Such a method is known from EP-A-0296377. The metal strip prevents material from sinking in the joint; the elastic sealing membrane provides the water seal and ensures the spread of the movement in the joint with the result that stress concentrations in the layer lying above are prevented due to small diffferences in elongations between said covered parts and the layer lying above. For larger differences in elongations problems of stress concentrations are expected, due to too high shear stresses. The elastic material in the recess can absorb movements in the ground below, without giving way. Use of the filling of the recess known from the above mentioned European patent application in water permeable road surfaces could lead to an unsafe situation, in which, when it rained, the motorist could suddenly be faced with a pool of water on the road surface before, after and above the joint. There could also be increased tire noise when passing over the joint.
The object of the invention is to solve this problem and to provide a water-permeable or water draining and low-noise filling of the recess at the site of the joint, without the elasticity and flexibility of said filling which is necessary in order to avoid cracks forming, being adversely effected.
According to the invention, the method is to this end characterized in that the recess above the membrane layer is filled with elastic hot-rolled asphalt of which at least the top layer is made of very open-textured elastic hot-rolled asphalt.
The metal strip prevents material from sinking in the joint. The elastic sealing membrane provides the water seal and ensures the spread of the movement in the joint, with the result that stress concentrations in the layers lying above are prevented. The elastic hot-rolled asphalt can absorb movements in the ground below, without giving way. This elastic material is preferably composed of a bottom layer of dense hot-rolled asphalt and a top layer of very open-textured hot-rolled asphalt. The elastic very open-textured hot-rolled asphalt of the joint seal abuts the very open-textured hot-rolled asphalt of the connecting road, so that there is no difference in sound production, and the horizontal water conveyance through the open-textured layer, viewed in the lengthwise direction of the road, is not interrupted. The elastic dense hot-rolled asphalt ensures that water is retained and can be drained through the elastic very open-textured hot-rolled asphalt.
If the vertical distance between the top surface of the road and the top surface of the bridge roadway part corresponds to the thickness of the very open-textured hot-rolled asphalt, the recess can be made right into the material of the road parts which are movable relative to each other. Space is then produced for a layer of elastic dense hot-rolled asphalt. If movements are very small, such a layer of dense hot-rolled asphalt is not necessary.
Securing means projecting into the joint are used to prevent shifting of the hard strip, without said strip being fixed.
The elastic sealing membrane can be made of a 3 to 30 mm thick layer of a bitumen emulsion or a plastic modified bitumen emulsion mixed with fine stone grit. Another possibility is for the elastic sealing membrane to be made up of a 3 to 30 mm thick layer of an emulsion based on polyurethane alone or mixed with a fine stone grit.
It is also possible for the elastic sealing membrane to be composed of several layers, in which case little or none of said emulsion is applied in the stone grit between the layers. This produces a very low shear strength between the two layers, with the result that the stresses in the elastic very open-textured hot-rolled asphalt lying above will be minimal.
Another embodiment is to apply a one to five millimetre thick emulsion layer between the above-mentioned two layers, which also achieves a low shear strength.
There are practical advantages if the recess narrows stepwise from top to bottom. This step form is not necessary.
The elastic, very open-textured hot-rolled asphalt can have the following composition:
stone chippings: 65-90 mass per cent, particle size 8-16 mm
sand: 0-20 mass per cent, granule size 0-3 mm
filler: 0-10 mass per cent, size < 63 µm
binder: 4-25 mass per cent
additions: 0-1 mass per cent,
the binder being composed of a mixture of bitumen and a natural rubber or elastomer, or a thermoplastic.
The admixture to the bitumen can be styrene butadiene styrene polymer (SBS), styrene butadiene rubber (SBR) or ethyl vinyl acetate (EVA), or ethylene propylene dimonomer (EPDM).
The above-mentioned additions (0-1 mass per cent) can contain glass fibres, mineral fibres, rubber particles, adhesion improvers, latex emulsions and bitumen emulsions.
The invention will now be explained in greater detail with reference to the figures.
Figure 1 shows a longitudinal section through two bridge roadway parts which are movable relative to each other.
Figure 2 shows a cross-section along the line II - II in Figure 1.
Figure 3 shows a longitudinal section through two bridge roadway parts which are movable relative to each other, in which the joint seal is of a different type.
The figures show two bridge roadway parts 1, 2 which are separated from each other by a joint 3. The normal road surface on the bridge roadway parts in Figure 1 comprises a bottom layer 4 of dense hot-rolled asphalt and a top layer 5 of very open-textured hot-rolled asphalt. The layer 4 is not present in Figure 3. In both cases the road surface on the bridge roadway parts abuts the ordinary road surface composed of a bottom layer of dense hot-rolled asphalt and a top layer of very open-textured hot-rolled asphalt. In Figure 3 the dense hot-rolled asphalt of the ordinary road surface is not continued on the bridge roadway parts, but lies with the end face against the vertical boundary of a bridge roadway part.
In Figure 1 a recess 6 is made in the asphalt above the joint 3. In Figure 2 this recess 6 continues over the hot-rolled asphalt of the bridge roadway parts.
An elastic sealing membrane layer 7 covers the bottom of the recess, and a metal strip 8 is placed in said membrane layer above the joint 3, which strip is connected to securing means such as a cord 8a, which prevents shifting of the strip. The membrane extends over the top surface of the strip.
The recess 6 is also filled with a bottom layer 9 of elastic dense hot-rolled asphalt and a top layer 10 of elastic very open-textured hot-rolled asphalt.
The open-textured layers 5 and 10 are the same thickness and abut each other accurately, so that the water seeping through said layers can flow away in the lengthwise direction of the road. It can be seen from the cross-section of Figure 2 that water which has collected on the top surface of the elastic dense hot-rolled asphalt layer can flow away in the crosswise direction through the elastic very open-textured hot-rolled asphalt to a channel 11 formed through the layer 10 not running through to the side boundary of said bridge roadway part 2.
Depending on the circumstances, it is also possible for layer 5 to have the composition of layer 10, and for these layers 5 and 10 to be applied in one go over the whole or part of the bridge roadway.
The membrane layer 7 runs through at the ends to the transition between the elastic dense hot-rolled asphalt and the elastic very open-textured hot-rolled asphalt.
It is possible in the absence of the dense hot-rolled asphalt on the bridge for the layer of elastic very open-textured hot-rolled asphalt to be placed directly on the membrane layer 7. In other words, in certain circumstances (very small changes in the width of the joint) the layer 9 in Figure 3 can be omitted.
The watertight membrane layer 7 can be a stress-absorbing membrane interlayer (SAMI) which is characterised not only by its watertightness, but also by a great elasticity, even at low temperatures.
The membrane is composed of at least one layer of a bitumen emulsion mixed with fine stone grit, in order to create a layer thickness. The layer thickness varies between 3 and 30 mm. If the membrane is made of at least two of these layers, a very low shear strength can be created between the two layers by applying the stone grit in a suitable manner, with the result that lower stresses in the very open-textured hot-rolled asphalt lying above this will be produced. In the zone of low shear strength hardly any bitumen emulsion is present between the stone grit, or an emulsion layer one to five millimetres thick is applied. The bitumen emulsion can be composed of a mixture of bitumen with SBS or bitumen with EVA, SBR or EPDM.
Another possibility is to replace the bitumen emulsion by polyurethane-based mixtures.
The elastic very open-textured hot-rolled asphalt has the following composition:
stone chippings: 65-90 mass per cent, particle size 8-16 mm
sand: 5-20 mass per cent, granule size 0-3 mm
filler: 4-10 mass per cent, size < 63 µm
binder: 4-10 mass per cent
additions: 0-1 mass per cent.
The binder can be composed of a mixture of bitumen with natural rubber or elastomer, or a thermoplastic, in particular with styrene butadiene styrene polymer (SBS) or with styrene butadiene rubber (SBR) or with ethyl vinyl acetate (EVA), or with ethylene propylene dimonomer (EPDM). The additions can contain glass fibres, mineral fibres, rubber particles, adhesion improvers, latex emulsions and bitumen emulsions. What is essential is that the mixture after compacting should have hollow spaces between 15 and 35 volume per cent.
The elastic dense hot-rolled asphalt differs from the elastic very open-textured hot-rolled asphalt in that the spaces between the larger pieces of chippings are filled with smaller pieces and sand. The mixture will therefore contain more sand and more smaller stone chipping parts than is the case with the elastic very open-textured hot-rolled asphalt.
The main advantage of the joint seal described is that the very open hot-rolled asphalt runs over the joint in such a way that the water drainage through this open-textured hot-rolled asphalt layer in the lengthwise direction of the road is uninterrupted and no noise peak is produced on passing over the joint. This advantage is obtained without detriment to the resistance to crack formation at the site of the joint.