Waterproofed Concrete Structure

Abstract

The concrete sublayer in a bituminous road or pavement structure is waterproofed using a preformed sheet material made up of a flexible sheet-like support (e.g., woven polypropylene mesh) having on its surface placed adjacent the concrete a waterproof pressure-sensitive adhesive membrane formed of a bituminous rubber composition, and on the other surface, a layer of bituminous composition to which has been added sufficient wax to render the composition non-tacky when cold, the wax-containing layer becoming tacky or pressure-sensitive at an elevated temperature.

Parent Case Text

This application is a continuation-in-part of my copending application, Ser. No. 803,438, filed Feb. 28, 1969 now U.S. Pat. No. 3,741,856, which is a continuation-in-part of my application, Ser. No. 676,652, filed Oct. 19, 1967, now abandoned.

Description

This invention relates to the sealing of the concrete layer in a composite building or civil engineering structure in which a layer of concrete is employed. More particularly, this invention pertains to the waterproofing of the concrete layer in such a structure using a waterproofing which is in the form of a preformed sheet-like structure. The sheet-like structure is designed in a particular manner to receive, and be bonded to, a layer of hot poured bituminous or asphaltic material such as a wear course of asphaltic concrete.

It is desirable to waterproof the concrete mass employed as a sub-base in a road or pavement structure, especially an above-ground road or pavement structure which is particularly susceptible to freezing. Bridge decks, for example, due to their elevation, tend to freeze faster than on-ground structures and consequently receive a comparatively larger application of the widely used de-icer, calcium chloride. Calcium chloride is, however, corrosive of the structural steel employed in the deck and, therefore, its penetration into and through cracks occuring in the concrete sublayer to the structural steel supporting the deck should be prevented.

The waterproofing of such a concrete layer is realized according to the invention by the use of preformed structures of pressure-sensitive adhesives. Such structures can be produced on a large scale in a factory and then used on site.

Reference is made to the accompanying drawing wherein

FIG. 1 is an enlarged cross sectional view of the structure of the invention, and

FIG. 2 is a sectional view in perspective of the structure of FIG. 1 installed in a road or pavement construction.

FIG. 2 is a sectional view in perspective of the structure of FIG. 1 installed in a road or pavement construction.

The structure comprises a sheet-like substrate and contiguous thereto, a membrane 2 of a waterproofing pressure-sensitive adhesive comprising a mixture of rubber and a bituminous material. (The terms "bituminous material" and "bitumen" are used in this specification inclusive of compositions and materials containing asphalt, tar or pitch). The surface of the substrate remote from the pressure-sensitive adhesive is coated with a layer 3 of a bituminous adhesive composition which is not pressure-sensitive adherent or tacky when cold but becomes tacky at elevated temperature, as when a hot bituminous or asphaltic mix 4 is poured thereon. Such an adhesive composition comprises a mixture of a normally tacky or pressure-sensitive bituminous material to which has been added an amount of a normally solid wax component sufficient to reduce the tackiness thereof. The rendering of this layer non-tacky by the addition of the wax permits, for example, asphalt-laying equipment to be driven thereover during the application of the hot asphaltic mix, following which the adhesive layer becomes tacky due to the elevated temperature of the asphaltic wear-layer. Activation of the tacky or pressure-sensitive quality of the adhesive composition by the hot asphaltic layer enables a strong bonding between the wax-containing adhesive layer of the waterproofing structure and the asphaltic wear course.

The bituminous material-rubber waterproofing adhesive layer is formed of natural or synthetic rubber, virgin or reclaimed, or mixtures thereof, blended into bitumen to provide a smooth mix. The ratio by weight of bitumen to rubber is suitably greater than 80:20, preferably up to 95:5, especially about 90:10. If desired, the membrane may be reinforced with asbestos fibers or other types of fillers. Generally, suitable compositions have softening points (measured by the Ring and Ball method) of 60.degree. to 140.degree., preferably 60.degree. to 110.degree.C. and penetration values of 50 to 400, preferably 150 to 300 at 25.degree.C. (100 g. 5 secs -- I.P. method). In order to give utmost sealing ability, especially after movement of the concrete layer, the waterproofing adhesive membrane layer should be least 0.025 cm. (0.010 inch) thick, preferably 0.063 to 0.50 cm. (0.025 to 0.20 inch) thick.

A wide variety of materials can be used as the sheet-like support. It is generally desirable that the support should be substantially impermeable to water. For many purposes, it is desirable that the support should be such that after application to the surface it is capable of stretching with movement of the concrete or other material, e.g., as a result of shrinkage, with maintenance of a moisture and moisture-vapor-proof seal. To this end, it is desirable that the combined structure of the support and the membrane should have, at 20.degree.C., an elongation at break of at least 300%, a tensile strength of at least 100 lb. per foot width (at least 1.5 kg. per cm. width) and an Elmendorf tear strength of at least 750 gm. However, where stretchability and flexibility are less important than other properties, supports not fulfilling these requirements can be utilized. For example, it is desirable for some purposes to use a metallic foil, particularly, of copper or aluminum, as the support.

The supports are generally films of natural rubber or of a synthetic organic polymer such as polyethylene, e.g., that commercially available under the trade name Polythene, polypropylene or other polyolefin, a polyamide, a polyester, e.g., polyethylene terephthalate, a polyurethane, polyvinyl chloride, a copolymer of vinyl chloride and vinylidene chloride, a synthetic rubber such as polychloroprene or butyl rubber, regenerated cellulose, cellulose ethers or cellulose esters. Inorganic or metallic supports can also be used. The support should be such that hot asphalt can be poured directly onto it without deleterious effect on the waterproof seal. For this purpose, the support should be able to resist, or be made able to resist, a temperature of at least 150.degree.C., preferably at least 175.degree.C., for asphalt mixes such as sand course asphalt, and even higher temperatures for hot asphalt (mastic), which is applied at temperatures up to 250.degree.C. A particularly suitable material for this purpose is one consisting of a woven fabric of polypropylene fibers. While cellular films can be used as supports, the supports are generally substantially incompressible and have a thickness of a most 0.25 inch (0.6 cm). Other sheet-like supports include woven and non-woven fabrics of inorganic or organic natural or synthetic fibers (i.e., staple fibers or continuous filaments), e.g., a woven fabric of fibers of one of the synthetic organic polymers already referred to, glass tissue, hessian, cotton or other fiber scrim or bituminous roofing felt.

The normally non-tacky layer deposited on the surface of the support remote from the bitumen-rubber waterproofing adhesive membrane is, as mentioned above, formed of a normally tacky or pressure-sensitive bituminous material to which has been added sufficient wax to render the bituminous matterial non-tacky. The precise amount of wax employed will vary depending upon the type of wax employed and the degree of reduction in tackiness desired. Generally from 1 to 10, preferably from about 2 to 5, parts by weight of bituminous per part by weight of wax is employed.

The wax employed are normally solid and possess melting points such that when mixed with the bituminous material, the coating will melt at the temperature of the bituminous or asphaltic wear coat mix deposited upon it. The wax-bitumen mixture preferably possesses a melting point of at least about 115.degree.F., preferably 174.degree.F. The waxes may be selected from any suitable source, for example, carnauba or candelilla or a mineral wax, e.g., montan wax or petroleum waxes such as paraffin and microcrystalline waxes. Normally solid synthetic waxes having the requisite melting point may also be employed such as the ethylenic polymers, e.g., "Carbowax," chlorinated naphthalenes and hydrocarbon type waxes such as prepared via the Fischer-Tropsch synthesis.

The thickness of the bitumen-wax layer may be varied, but in all cases the thickness should be at least sufficient to form a bond with the asphaltic mix deposited thereon. Generally, a thickness of at least about 0.001 inch, preferably at least about 0.002 inch is employed.

The waterproofing structures useful in the invention may be produced in the factory in the form of laminates of the various layers described above. The widths of the structures may vary widely, e.g., from 1 to 48 inches (2.5 to 120 cm.); generally they will be at least 2 inches (5 cm.) wide, e.g., 6 to 36 inches (15 to 90 cm.) wide, with widths in the upper part of this range, e.g., 24 to 36 inches (60 to 90 cm.), being preferred. The thickness of the novel structures can also vary widely but will generally be from 0.01 to 0.25 or 0.35 inch (0.025 to 0.6 or 0.9 cm.).

To permit storage and handling, the normally pressure-sensitive adhesive layer may be covered with a protective covering or coating which can be removed at the job site without damage to the membrane. A wide variety of materials can be used to provide protective coatings in the novel structures of the invention. Paper having a release coating thereon, e.g., siliconized paper or suitable material formulated from or with polytetrafluoroetylene, is satisfactory. Other materials include treated or modified films of organic polymers.

In use, the protective coating is simply removed from the waterproofing structure and the structure applied to the concrete layer 5, e.g., the concrete sublayer which is supported by the structural steel members. A primer coat, for instance, liquid bituminous composition or neoprene-based composition may first be applied if desired, to the concrete layer. The waterproofed structure is then in position for deposition of the hot asphaltic wear course mix directly upon the wax-bitumen coating which renders the coating sufficiently tacky or pressure-sensitive to form a strong bond with the wear coat.

The invention is illustrated by the following example.

EXAMPLE

To one side of a sheet (10 mils thick) of woven polypropylene mesh is applied a coating (60 mils thick) of a pressure-sensitive bituminous adhesive composition containing 7 parts by weight of rubber and 93 parts by weight of asphalt. To the other side of the mesh sheet is applied a hot coating (2 mils thick) of an asphalt-paraffin wax mixture. The mixture was prepared by blending 50 gallons of asphalt with 120 pounds of paraffin wax. The wax-asphalt mix had a melting point of about 180.degree.F. When cooled, the wax-bitumen coating is non-tacky to the touch and will bear traffic, e.g., asphalt laying equipment over it without the coating being lifted from the sheet.

The resulting waterproofing laminate structure is applied to the concrete sublayer of a conventional bridge deck construction, with the rubber-asphalt adhesive surface adjacent the concrete. A primer coat of, e.g., neoprene-based compound can be applied to the concrete before applying the laminate if desired. A wear-course comprised of one or two coats of hot (180.degree.F.) asphaltic concrete is then layed down over the wax-asphalt layer forming a strong unitary bond between the waterproofing membrane structure and the wear course.

Claims

It is claimed:

1. In combination (a) a structure comprising a flexible sheet-like support, on one side of the support a layer of bituminous composition comprising a mixture of a bitumen and wax, wherein the ratio by weight of bitumen to wax is from about 1 to 10 parts bitumen per part of wax, and on the other side of the support a waterproof pressure-sensitive adhesive membrane formed of a bituminous rubber composition at least 0.025 cm thick which is a blend of a rubber selected from the grouping consisting of a natural rubber, synthetic rubber, or combinations thereof, with a bitumen, the ratio by weight of said bitumen to said rubber being greater than 80:20; (b) a concrete surface to which the face of said pressure-sensitive membrane is adherent; and (c) a layer of load bearing, hot poured asphaltic concrete deposited over the adherent to the bitumen-wax layer.

2. The combination of claim 1 wherein the support is a woven fabric of polypropylene fibers.

3. The combination of claim 1 wherein a layer of bituminous or neoprene-based primer composition is employed between said concrete and said membrane.

4. The combination of claim 3 wherein the melting point of the mixture of wax and bitumen is at least 115.degree.F.

5. The combination of claim 1 wherein the melting point of the mixture of wax and bitumen is at least 175.degree.F.

6. The combination of claim 1 wherein said wax is paraffin wax.

7. A waterproofing structure comprising a flexible sheet-like support, on one side of the support a layer of a bituminous composition which is not normally tacky but which becomes tacky at an elevated temperature comprised of normally tacky bitumen to which has been added sufficient wax to render the mixture non-tacky, and on the other side of the support a wateroroof pressure-sensitive adhesive membrane formed of a bituminous rubber composition at least 0.025 on thick which is a blend of a rubber selected from the group consisting of a natural rubber, synthetic rubber or combinations thereof and a bitumen, the ratio by weight of said bitumen to said rubber being greater than 80:20.

8. The structure of claim 7 wherein said support is a woven polypropylene mesh.

9. In combination (a) a structure comprising a flexible sheet-like support, on one side of the support a layer of a bituminous composition comprising a mixture of a bitumen and a wax wherein the ratio by weight of bitumen wax is from about 1 to 10 parts bitumen per part of wax, and on the other side of the support a waterproof pressure-sensitive adhesive membrane formed of a bituminous rubber composition at least 0.025 cm thick which is a blend of a rubber selected from the group consisting of a natural rubber, synthetic rubber, or combinations thereof with a bitumen, the ratio by weight ofsaid bitumen to said rubber being greater than 80:20 and/less than 95:5; (b) a concrete surface to which the face of said pressure-sensitive adhesive membrane is adherent; and (c) a layer of load bearing, hot poured asphaltic concrete deposited over and adherent to the bitumen-wax layer.

10. A waterproofing structure comprising a flexible sheet-like support on one side of the support a layer of a bituminous composition which is not normally tacky but which becomes tacky at an elevated temperature comprised of a normally tacky bitumen to which has been added sufficient wax to render the mixture non-tacky, and on the other side of the support a waterproof, pressure-sensitive adhesive membrane formed of a bituminous rubber composition at least 0.025 cm thick which is a blend of a rubber selected from the group consisting of a natural rubber, synthetic rubber, or combinations thereof with a bitumen, the ratio by weight of said bitumen to said rubber being greater than 80:20, the face of said membrane remote from said support being covered with a protective covering easily removable from the membrane without damage thereto.

11. The structure of claim 10 wherein said protective covering is paper having a layer of release coating on its surface adjacent said membrane.