ASPHALTIC PLUG EXPANSION JOINT WITH FLEXIBLE NOSING The present invention relates to expansion joints, and in particular, but not exclusively, to expansion joints for use in road bridges. When building a road bridge or similar structure, it is necessary to incorporate one or more expansion joints in order to accommodate thermal expansion and contraction of the bridge deck, which is generally made out of concrete. An expansion joint basically comprises a gap between sections of the bridge deck, the gap being provided with a relatively flexible cover at the level of the road surfacing. This cover is necessary firstly in order to present a substantially continuous road surface so as to allow safe and comfortable passage of traffic, and secondly in order to prevent leakage of rain water into the gap from the road surface, which can lead to corrosion of a reinforced concrete deck.

There are a number of types of bridge deck expansion joint known in the art. These range from a simple gap provided with a layer of waterproofing material which is then overlaid with a road surfacing material to more complex arrangements in which the deck gap is bridged by elastomeric elements provided with metal runners embedded in a resin mortar.

One known type of expansion joint, such as that disclosed in EP 0 000 642, is generally called an asphaltic plug joint. In this type of joint, a channel is cut in the normal road surfacing material along the line of the expansion gap, leaving a section of the concrete deck on either side of the expansion gap bare. A deck plate is then placed on the deck so as to cover the expansion gap, and a filling material comprising an asphaltic mixture of suitable aggregate and binders is poured onto the deck plate so as to fill the exposed area up to the level of the road surface. The

asphaltic mixture is, however, vulnerable to damage initiated by carriageway failures such as rutting or tracking which can be caused by passing traffic and transferred across the interface between the asphaltic plug and the road surfacing material. If the asphaltic plug is damaged, the integrity of the waterproof seal over the expansion joint is compromised. If water is allowed to breach the seal for a protracted period of time, serious damage can be caused to the bridge structure through the corrosion of reinforcing bars and the like. Furthermore, failure of the asphaltic plug can result in damage to the carriageway through the transfer of the structural failure across the interface between the asphaltic plug and the road surfacing material. This problem is becoming progressively more severe as the weight and volume of modern-day traffic increases.

It is possible to remedy the rutting or tracking by resurfacing the asphalt plug and/or the adjacent sections of the road surface, but this fails to address the underlying cause of the problem and is an expensive and cumbersome way of ensuring the continued integrity of the expansion joint.

We have found that the discontinuity in flexibility at the interface between the road surface and the asphaltic plug makes a significant contribution to the transference of structural failures between the carriageway and the asphaltic plug.

According to a first aspect of the present invention, there is provided a seal for a road deck expansion joint, which comprises an asphaltic mass in the form of a strip disposed between two strips of a flexible, non-asphaltic material, the seal being dimensioned so as, in use, to be disposed in a channel extending through the full depth of a road surfacing material across the width of the road deck at the

location of the joint.

The flexible non-asphaltic material forms a nosing which acts as a restraint between the surface of the carriageway and the asphaltic material, allowing their respective degrees of flexibility to act in isolation and thereby reducing the transference of structural failure from one to the other. The flexible non- asphaltic material advantageously comprises an epoxy resin material, for example a two-part component modified with polyurethane and filled with graded aggregate, or an acrylic-based resin material. Other materials with suitable physical properties may also be used.

In one embodiment of the invention, the edges of the channel are substantially perpendicular to the surface of the road deck, and the strips of flexible non-asphaltic material when installed extend over the full depth of the road surfacing material at a height- to-width ratio of, for example, 1:1.25. Alternatively, the edges of the channel may be stepped, for example with the width of the channel in a base course of the carriageway being less than the width of the channel in an overlying wearing course. In this embodiment, the strips of flexible non-asphaltic material when installed extend only to the depth of the carriageway wearing course and to the width of the step.

According to a second aspect of the present invention, there is provided a method of sealing a road deck expansion joint, the method comprising the steps of: (i) cutting first and second channels in the road surfacing material across the width of the road deck on either side of the location of the expansion joint; (ii) substantially filling each channel with a flexible non-asphaltic material; (iii) removing the road surfacing material from the road deck in the region between the first and second channels to form a third

channel; and (iv) substantially filling the third channel with an asphaltic material.

As discussed above, the flexible non-asphaltic material is preferably an epoxy or acrylic resin material, although other suitable materials may be used. The first and second channels may be cut to the full depth of the road surfacing material, or may be cut only to the depth of the carriageway wearing course. Where the flexible material is an epoxy or acrylic resin applied in fluid form, a polystyrene or similar barrier may advantageously be provided along the edges of the first and second channels closest to the location of the expansion joint before the flexible material is applied. The barriers avoid adhesion of the flexible material to the road surfacing material at these edges upon setting, and thereby facilitate subsequent removal of the road surfacing material between the first and second channels without disrupting the flexible material once it has set. The polystyrene barriers will generally be burned away before the third channel is filled with the asphaltic material.

For a better understanding of the present invention, and to show how it may be carried into effect, reference will now be made, by way of example, to the accompanying drawings, in which:

FIGURE 1 shows an asphaltic plug expansion joint provided with a full depth flexible nosing; and FIGURE 2 shows an asphaltic plug expansion joint provided with a flexible nosing only within the wearing course of the carriageway.

With reference to Figure 1, an expansion joint comprises a channel 1 cut through the road surfacing material 2 down to the level of the bridge deck 3 along the line of the expansion gap 4. The gap 4 is covered

with a deck plate 5. The central volume of the channel 1 is filled with an asphaltic material 7 comprising suitable binders and aggregate and the edge volumes 6 of the channel 1 are filled with an epoxy resin material 8. The deck plate serves to cover the expansion gap in order to prevent leakage through the gap of the asphaltic mixture 7 while it is in a fluid state.

Figure 2 shows an expansion joint similar to that shown in Figure 1, except in that the edge volumes 6' of the channel 1 extend only to the depth of the carriageway wearing course 9.

The bridge deck 3 and/or the edges 10 of the channel 1 may be provided with a keying pattern, such as a number of longitudinal grooves (not shown) in order to improve the bonding of the asphaltic material 7 and/or the epoxy resin material 8.