Spring Bedding

Abstract: An anhydrous viscoelastic buffer joint comprises a filling means of viscoelastic bituminous material (2) between the floor slab (8) including the joint slit and the upper zone covered by the vehicles; it further comprises drainage and canalization systems (16', 16''; 18', 18''; 19', 19'') for the downflow of water in the zone of the joint.

Description: The present invention relates to an anhydrous viscoelastic buffer joint employed in the field of road construction works; more particularly it relates to a joint to be employed in the construction of bridges for constituting a continuous connection means for road traffic and a means for controlling the water flow at the site of the joint itself, so as to direct it towards water collecting and drainage ducts. In bridge constructions, at the site of connection between constituent elements, there are provided connection means which have the task of forming superficial continuity elements for the girders between which they are interposed, insuring at the same time that the water coming from the surface and the paving does not come into contact with the structures making up the work. The detrimental effects produced by said water penetration are particularly harmful in presence of salts usually employed to defrost the road wearing course. At the present state of the art, there are employed as continuity elements certain viscoelastic samples made of a bituminous material, which are placed directly on the floor slab in presence of a simple waterproofing system realized through a sheath or a caulking with a superimposed sheet metal, said system being located centrally and including lateral drainage means usually in the form of tubes provided with microslots. This construction permits in fact to obtain a good continuity as regards the comfort during passage of a motor vehicle on this road section, but often it doesn't insure waterproofing and the presence of the drainage means is not effective for collecting the water flow inside the buffer, so that the reinforced concrete structures and particularly the floor slab are frequently wetted with water which occasionally may be added with highly corrosive defrost salts, and this may have serious consequences on structural integrity of the girders and of the bridge itself. EP-A-0 444 236, which is regarded as the closest prior art, discloses an expansion joint between two adjacent elements of a bridge, wherein in a trench coinciding with the hollow space of gap between the two bridge elements, there are filled two layers consisting of a lower, highly viscoelastic layer, and an upper wearing course with low viscoelastic properties, and therefore rigid and strong. Two excavated strips of highly deformable material are located on both sides of the top layer. Mechanical and thermal deformations are absorbed by the lower highly viscoelastic layer and by the two strips located on both sides of the top layer. There are also provided one or two Z - shaped outlets collecting the liquid seeping through the featheredge. Whilst the problem of the integrity of the wearing course at the joint is solved by the two strips, the problem of water stagnation at the joint can be avoided by the provision of improved means. In fact, for large amounts of liguids the Z-shaped outlets may not be sufficient to drain these liquids away from the reinforced concrete or metal structure of the bridge, in order to prevent corrosion. An object of the present invention is that of providing a viscoelastic buffer joint which besides establishing a good continuity of the superficial butiminous wearing course, does not allow water flows to come into contact with the reinforced concrete making up the road work. Another object of the present invention is that of providing a viscoelastic buffer joint whose laying is quickly obtained by means of usually employed constructive techniques, and which has an acceptable, i.e. limited cost, and allows an easy maintenance. These objects are solved by the features of claim 1. For the sole purpose of better explaining the present invention and without limiting thereby the field of possible applications and the field of possible variations of its basic configuration, in the following a description will be made of a preferred embodiment of the anhydrous viscoelastic buffer joint according to the invention; said description refers to Fig. 1 in which a transversal section of the joint itself is shown. In said figure the sectional view 1 shows the viscoelastic material which makes up the very buffer 2 which is usually formed by modified bitumen including various elastomers and polymer plastics mixed with aggregate. There are also shown for clarity, the caulking 5 and the sheet metal or reinforced bituminous sheath 6, and also the drainage means 7' and 7", already known at the present state of the art for forming the current buffer joints. The drawing puts into evidence fundamental constituent elements as for example the floor slab 8 and the binder layers 9 and wear layers 10 forming the bituminous wearing course. Between the floorslab 8 and the viscoelastic bituminous material 2 there are interposed "recessed zones" 11' and 11'' filled with bituminous drainage conglomerate and separated from the viscoelastic material of the buffer, by means of a layer 12 of modified bitumen, said recessed zones being laid on piers or blocks with opposite slanted surfaces 13, 13' formed by fiber reinforced mortar and covered by an elastic bituminous sheath 14, as for instance bituthene HD. An optimum waterproofing is obtained by a constructive tecnique which provides a rough surface 15 of the floor slab, so that on said very rough surface the fiber reinforced mortar of the piers 13, 13' having oppositely slanted surfaces, may generate higher frictional forces. The recessed zones 11' and 11'' lead to flaring holes 16' and 16'' located at the lowest portions of the recessed zones, which allow to direct the water collected by the geo-textile filters 17' and 17'' of the drainage material, into the PVC downflow tubes 18', 18", and onto the PVC collection channels 19', 19". This sort of conveying the water along specific tubes and channels 18", 18'', 19', , 19", is extremely advantageous with regard to waterproofing, since it allows to drive the collected water flow away from the structures of reinforced concrete. It must be reminded again, that this description is given only for a preferred configuration embodying the invention, which is illustrative, i.e. non-limitative, like the mentioned materials, which refer to the ensemble of construction materials most used in road works nowadays. An anhydrous buffer joint of this kind has the advantage of being easily realized by means of the usual techniques employed in the building industry. Furthermore, it is quickly installed, so that it will have a reduced interference with traffic.

Claims: An anhydrous viscoelastic buffer joint, comprising a bituminous viscoelastic material (2) forming the wearing course at the region of the joint, characterized in that it comprises a separation means between the floor slab (8) and said bituminous viscoelastic material (2), whereby said separation means includes blocks or piers (13', 13") having opposed slanted upper surfaces and being formed by fiber reinforced mortar, covered with an elastic bituminous sheath (14) wherein recessed zones (11'; 11") formed between the said slanted surfaces and the bottom surface of said bituminous viscoelastic material are filled with a bituminous drainage conglomerate separated from the above viscoealstic bituminous material (2) by means of a layer (12) of modified bitumen, said recessed zones downwardly leading to flaring holes (16', 16") located at the lowest portions of the recessed zones and provided with geo-textile filters (17'; 17") for the bituminous drainage conglomerate said flaring holes (16',16") leading in downflow tubes (18'; 18") extending through said floor slab (8) with collection channels (19' ; 19") arranged thereunder.

Inventors: CAMOMILLA GABRIELE, ROMAGNOLO MARIANO, CAMOMILLA, GABRIELE, ROMAGNOLO, MARIANO
Applicants: AUTOSTRADE CONCESS CONST, AUTOSTRADE CONCESSIONI E COSTRUZIONI AUTOSTRADE S.P.A.
Application year: 1995
Main classification: E01D19
IPC codes: E01D19