GB2279374A - Expansion joints - Google Patents

Abstract

An expansion joint comprises a resin mixed with rubber in particulate, fibrous, powder or like form and includes a multiplicity of discrete voids 16 which may be filled with a compressible medium, e.g. air or polystyrene or polyethylene spheres or beads. A joint in a bridge or road between concrete sections 1, 2 with bituminous surfaces 4, 5 may include an elongate elastomeric seal 7, a steel bridging plate 12, and a debonding tape 13; also a resin/bauxite skim layer 15. <IMAGE>

Description

IMPROVEMENTS IN AND RELATING TO EXPANSION JOINTS This invention relates to joints to be positioned between adjacent spaced sections of a structure. More particularly, but not exclusively, the invention concerns an expansion joint to be positioned between road sections and more especially to joints to be provided on bridges and other structures.

As exemplified in our Patent GB 2060734, the provision of a joint between road sections, particularly on bridges, poses a number of well recognised difficulties. A predominant difficulty arises from the requirements that the joint must act as a sealant and must also be able to accommodate variations in the gap between the road or bridge sections while maintaining continuity of the road surface. More especially, the joint itself must be capable of accommodating changes in ambient temperature and any corresponding changes in gap width without loss of the essential adhesion between the joint and the adjoining road or bridge surfaces and without loss of integrity.

The expansion joint disclosed in our Patent GB 2060734 is what is known as a mechanical joint which comprises an elastomeric sealing member retained in place by a resin mortar bonded to the member by way of metal end plates. The present invention is directed more specifically to non-mechanical expansion joints which essentially comprise an elastomeric or visco-elastic sealing member located in the gap between adjoining road or bridge sections and retained in place within a prepared trench typically by means of an asphaltic aggregate material.

While relatively inexpensive to produce and install, such visco-elastic asphaltic joints are generally highly susceptible to damage caused by variations in ambient temperature. Thus, in hot weather the plasticity of presently known asphaltic joints increases to a point where traffic loading may cause severe deformations to occur in the joint surface which tend to gravity to the road or bridge borders and in cold weather the joints tend to harden to the point where they may break away from the adjoining road or bridge surfaces thereby enabling water to enter the joint structure adversely effecting its integrity. Known joints consequently require relatively frequent attention and replacement.

As will be appreciated, the problems identified above are occasioned essentially because of changes in joint stiffness and a consequent inability to provide an effective seal and to accommodate linear variations under differing temperature conditions.

The present invention sets out to provide an expansion joint which meets these criteria and does not suffer from, or at least alleviates, the problems identified above.

According to the present invention in one aspect there is provided an expansion joint whose composition comprises a resin mixed with rubber in particulate, fibrous, powder, or like form and includes a multiplicity of discrete voids which may be filled with a compressible medium.

The rubber is preferably in powder form although regular or irregular shaped rubber particles or grains or fibres may be employed instead of or in addition to powdered rubber.

The resin may be a two component formulation comprising a flexibilised liquid epoxy resin hardened by a modified or extended aliphatic or cycloaliphatic polyamine. Other resins can, however, be employed, theset, including epoxy polyureas, polyurethanes, acrylics and polyesters, or indeed one component visco-elastic materials exhibiting similar properties to such flexible resins.

The compressible medium present within the voids may comprise air or other compressible material. Thus, the voids may be produced by an aeration process by, for example, the employment of a foaming agent or by compressible void fillers. Alternatively, or additionally, the voids may comprise a multiplicity of compressible pellets or granules or the like bordered by, for example, a thin walled plastics material e.g. polyethylene, or expanded polystyrene spheres or beads.

A skim coating of, for example, bauxite and resin may be applied to the joint surface for wearing purposes. The skim may be voided.

The resin/rubber joint composition may infill a trench cut into adjoining road or bridge sections above an expansion gap provided between the road or bridge sections. An elongate elastomeric sealing member may be positioned within the expansion gap and may be covered with a bridging plate before the trench is infilled with the joint composition. A debonding tape or the like may be applied to the exposed upper surface of the bridging plate and/or any exposed surface of the elastomeric sealing member before infilling occurs.

The elastomeric sealing member may include elongate outwardly extending lip sections which overlie the upper surfaces of the adjoining road or bridge sections, which border the expansion gap. Sealing members not having such lip sections may, however, be employed. Indeed, it will be appreciated that sealing members having a variety of cross-sections may be employed.

Typically, the trench is of a width of the order of 325mm. Typical preferred widths lie within the range 300mm to 350mm. Later developments may look to reduce the width of joint to 250mm or even 200mm to reduce the deformation of the join in accommodating wheel loads.

Joints of widths of 500-600mm and higher may be used in replacing other failed joints where dictated by the width of the existing joint. Joints of varying stiffness may be considered beneficial in such wide joints and indeed standard width joints to a lesser effect.

The invention will now be described by way of example only with reference to the accompanying diagrammatic drawing illustrating in cross section a joint in accordance with the invention positioned between adjacent road or bridge sections.

In the drawing the road or bridge sections are indicated by reference numerals 1,2. These sections are conventiqnally of concrete set in situ upon underlying decking (not shown). The sections are spaced in accordance with accepted road making practice by a gap 3 to accommodate thermal expansion or contraction produced by changes in ambient temperature and movement due to passage of live traffic. Typically, the gap width is of the order of 50mm at average ambient temperature.

Overlying the concrete sections 1,2 are bituminous sections 4,5, whose upper surfaces comprise the wearing surface of the bridge or road. The sections 4, 5 may alternatively be provided with a separate dressing to define the wearing surface. The bituminous sections 4, 5 are spanned by a prepared trench 6. As shown in the drawing the width of the trench 6 exceeds that of the gap 3. Typically, the trench width is between 150mm and 350mm, but may be larger.

Located within the gap 3 is an elongate elastomeric seal 7 which extends over substantially the entire length of the gap 3. The elongate seal 7 conventionally comprises an extrusion which includes a hollow mid section 8 from which protrudes a plurality of outwardly extending elastomeric wings 9 which bear against the adjoining faces of the sections 1,2 to provide an effective and flexible seal therebetween. Seals having other sections may, however, be employed. The elongate seal also includes two outwardly extending webs 11 which lie over the upper surfaces of the sections 1,2 bordering the gap 3. These webs 11 may be secured to the sections by a suitable adhesive. The purpose of this seal is to provide a secondary sealing member in the unlikely event of the failure of the aerated resin joint.

A bridging plate 12 of, for example, steel is positioned over the webs 11 of the elongate sealing member to provide a cover for the seal 7. As will be seen from the drawing, the bridging plate 12 does not extend to the edges of the webs 11 of the seal 7, these and the upper surface of the plate itself being covered by a debonding tape 13.

Once the structure described is in place, the trench 6 between the adjoining bituminous sections 4,5 is filled with a joint composition which essentially comprises a mixture of a resin, rubber in powdered, fibrous or particulate form, and a multiplicity of voids 16 which may be filled with a compressible medium. A skim coating 15 of, for example, bauxite and resin is applied to the upper surface of the joint for wearing purposes. The skim coating 15 may be voided.

The resin may comprise two separate components which cure only after mixing and which conveniently are mixed immediately before casting in the trench 6 to form the required expansion joint. Such a resin is described in our Patent GB 2060734.

As stated in this Patent, the first component may comprise a flexibilised liquid epoxy resin and the second component may comprise a modified and extended aliphatic or cycloaliphatic polyamine.

The first component may be a mixture of polyureides and an epoxy resin and may include extenders and plasticisers to reduce cost and to adjust physical properties.

Conveniently this component may be obtained by mixing 20 to 55 parts of a liquid epoxy resin, or other similar resin and 45-80 parts of a polyisocyanate containing 2-6% of NCO groups.

Examples of suitable polyisocyanates are prepolymers of toluene di-isocyanate and polyethers, preferably straight chain polyethers based on polyoxypropylene, polyoxybutylene or copolymers of polyoxypropylene and polyoxybutylene with polyoxyethylenes. Instead of polyethers, one could use polyesters, although the former are preferable because of their better resistance to hydrolysis and their lower viscosity.

Plasticisers or modifiers may be added to the first component to adjust viscosity to the desired level; examples of these include dibutyl phthalate, dioctyl phthalate, dioctyladipate Dutrex (RTM), high boiling point aromatic process oils and polyisobutylenes.

Modifiers may be added to the second component in order to reduce the cost of the end product whilst improving the wettability of the concrete or other surfaces of the sections to which the resin must adhere and also accelerate the curing for the resin system.

As mentioned previously, the resin described above is referred to in more detail in our patent GB 2060734. Other resins may, however, be used, these including acrylics, polyesters, polyurethanes, epoxys and resins comprising polyureas or indeed one component visco-elastic materials exhibiting similar properties to such resins.

The rubber content of the joint composition is preferably in powder form, although particulate or fibrous rubber may be employed additionally or alternatively.

The compressible filling material for the voids may comprise air or a compressible medium such as polystyrene pellets or balls or thin walled polyethylene pellets.

Other compressible materials may be employed. Preferably, the voids are distributed relatively evenly through the joint. Where the voids are to be filled with air, the joint composition may be subjected to aeration when in situ within the trench. Alternatively, or additionally, a foaming agent may be added to the composition prior to casting.

Examples of this of this jointing composition are set out below.

EXAMPLE 1 A mix of the following constituents was produced: Flexibilised epoxy resin compound 40.0% by weight Coal tar extended amine hardener compound 22.5% by weight Rubber powder, 20 mesh 35.0% by weight Polystyrene beads, lmm 2.5% by weight The epoxy resin was heated to 400C and the rubber powder added and dispersed in the resin by mechanical means. The polystyrene beads were then added to the mix and dispersed before addition of the pre-heated amine hardener compound.

The jointing composition produced was subsequently poured into a trench and allowed to cure in situ at ambient temperatures.

EXAMPLE 2 A mix of the following constituents was produced: Flexibilised epoxy resin compound with viscosity modifier 60.0% by weight Coal tar extended amine hardener compound 26.0% by weight Rubber powder, 40 mesh 13.0% by weight Polystyrene beads, 5mm 1.0% by weight The constituents were mixed at ambient temperatures, in the same order as given above in Example 1.

Following mechanical dispersion of the constituents the jointing composition was poured into a trench and allowed to cure in situ at ambient temperatures.

In use, the presence of the voids 16 in addition to the rubber powder, fibres or particles, lends added flexibility to the joint to accommodate dimensional variations covered by changes in ambient temperature. It has been found that the addition simply of rubber in particulate form is not in itself sufficient to provide the required elasticity during temperature variations. The presence of voids filled with a compressible medium such as air or polystyrene pellets or balls has been found to be essential to enable the elastomeric joint to accommodate dimensional variations over relatively long time periods and to maintain its overall integrity.

It is to be understood that the foregoing is exemplary of expansion joints in accordance with the invention and that modifications can readily be made thereto without departing from the true scope of the invention.

Claims (19)

1. An expansion joint comprising a resin mixed with rubber in particulate, fibrous, powder or like form and including a multiplicity of discrete voids which may be filled with a compressible medium.

2. An expansion joint according to Claim 1, wherein the resin is a flexible or visco-elastic material.

3. An expansion joint according to Claim 1 or 2, wherein the rubber is in powder form.

4. An expansion joint according to any one of the preceding claims, wherein regularly or irregularly shaped rubber particles or grains or fibres are employed.

5. An expansion joint according to any one of the preceding claims, wherein the resin includes one or more of: epoxy resins, polyureas, polyurethanes, acrylics, polyesters or one component visco elastic materials exhibiting similar properties to such flexible resins.

6. An expansion joint according to any one of the preceding claims, wherein the resin comprises a two component formulation comprising a flexibilised liquid apoxy resin hardened by a modified or extended aliphatic or cycloaliphatic polyamine.

7. An expansion joint according to any one of the preceding claims, wherein the compressible medium present within the voids comprises air.

8. An expansion joint according to Claim 7, wherein the voids are produced by aeration.

9. An expansion joint according to any one of the preceding claims, wherein the voids comprise a multiplicity of compressible pellets, granules or the like bordered by a thin walled plastics material, or expanded spheres or beads.

10. An expansion joint according to any one of the preceding claims, wherein a skim coating is applied to the joint surface.

11. An expansion joint according to Claim 10, wherein the skim coating is voided.

12. An expansion joint according to any one of the preceding claims, wherein the resin/rubber joint composition in use infills a trench cut into adjoining road or bridge sections above an expansion gap provided between the road or bridge sections.

13. An expansion joint according to Claim 12, wherein an elongate elastomeric sealing member is positioned in use within the expansion gap.

14. An expansion joint according to Claim 13 in which the elongate elastomeric sealing member is covered in use with a bridging plate.

15. An expansion joint according to Claim 14 wherein a debonding tape or the like is applied to the exposed upper surface of the bridging plate and/or any exposed surface of the elastomeric sealing member before infilling occurs.

16. An expansion joint according to any one of Claims 13 to 15, wherein the elastomeric sealing member includes elongate outwardly extending lip sections which overlie the upper surfaces of the adjoining road or bridge sections which border the expansion gap.

17. An expansion joint according to any one of Claims 12 to 16, wherein the width of the trench is from substantially 300mm to substantially 350mm.

18. An expansion joint according to Claim 17, wherein the width of the trench is substantially 325mm.

19. An expansion joint substantially as hereinbefore described with reference to the accompanying Drawing.