Traffic bearing expansion joint cover and method of preparing same

Each of the recessed, confronting edges of adjacent concrete slabs in a roadway or the like has secured therein by a high density reinforced grout an elongated, rigid, prefabricated or precast edger strip, which also has an elongate recess in the edge thereof which faces on the space between the slabs. An elongate, semi-rigid, prefabricated cover member, which is generally T-shaped in cross section, has its upper, plate-shaped section positioned over the upper end of the space between the slabs so that opposite sides thereof project part way into the recesses in the edger strips, and has its downwardly projecting web section embedded in a sealing compound positioned between the confronting ends of the slabs. Remaining portions of the recesses in said edger strips are filled with a low modulus urethane compound.

BACKGROUND OF THE INVENTION 
This invention relates to concrete highways or roadways, and more 
particularly to an improved, long-lasting cover for highway expansion 
joints, and a method for installing such covers between adjacent concrete 
slabs of a road or highway. 
It has long been customary to form modern highways, and associated bridges 
and overpasses, from concrete slabs, which are poured one after the other 
along the length of the proposed highway or overpass to form a firm 
roadbed. Since concrete tends to contract and expand in response to 
falling and rising temperatures, respectively, it also has long been 
customary to interpose between the confronting ends of adjacent slabs 
resilient expansion joints. Such joints permit the slabs to expand and 
contract without unduly distorting the horizontal surface of the roadway; 
and they also prevent debris and water from entering the spaces between 
adjacent slabs. In the case of overpasses such joints prevent water and 
debris from dropping onto traffic passing beneath an overpass; and in the 
case of conventional roadways they prevent ice from forming between 
adjacent slabs and possibly interfering with the normal expansion and 
contraction of the slabs. 
Among the solutions heretofore proposed, U.S. Pat. No. 4,080,086 suggests 
using elongated anchor pads, which are secured by studs and nuts to the 
upper surfaces of adjacent concrete slabs at the confronting ends thereof. 
These pads are connected to opposite sides of a flexible or resilient 
sealing member, which is thus supported by the anchor pads sealingly 
between the adjacent slabs. The disadvantage of this apparatus is that it 
requires a considerable amount of manual operations for bolting or 
mechanically securing the anchor pads to the concrete slabs. 
In the structure taught by U.S. Pat. No. 4,285,612, a silica-epoxy mortar 
material is poured and tamped into confronting, notches or recesses formed 
in the confronting surfaces of adjacent slabs, and is allowed to set. 
Thereafter an elongate, resilient seal is inserted into the space between 
the strips of mortar, and a filler material is pumped into a bore in the 
center of the seal thus forcing the seal to expand outwardly into sealing 
engagement with the confronting edges of the now-cured mortar strips. With 
this construction, however, water or moisture is prevented from entering 
the space between the slabs only so long as the sides of the resilient 
seal remain sealingly engaged with the confronting surfaces of the strips 
of mortar. 
The U.S. Pat. No. 4,098,047 teaches the use of an elongate, resilient, 
tubular seal having laterally extending side flanges, which are secured by 
a grouting material in opposed, longitudinally extending recesses formed 
in the confronting ends of a pair of adjacent concrete slabs. The tubular 
seal itself, however, remains exposed to the elements. U.S. Pat. No. 
4,295,311 illustrates a somewhat similar expansion joint, but the latter 
joint is prefabricated all in one piece, and is then adhered by a plastic 
in confronting recesses formed in the adjacent concrete slabs. 
U.S. Pat. No. 4,601,604 discloses a method of covering a resilient 
expansion joint or seal by pouring thereover a polyurethane layer, placing 
an extruded, plastic core over this layer, and then covering the core with 
still another layer of plastic, such as a fluid-polymer. At least two 
layers are thus poured over the resilient expansion joint after the latter 
has been inserted between the confronting surfaces of adjacent slabs. 
Instead of using a resilient seal between the confronting surfaces of 
adjacent slabs, U.S. Pat. No. 4,279,533 suggests securing a steel plate 
over the gap between the adjacent slabs, and then securing the plate in 
place with a plastic material. 
Despite all the efforts heretofore made to provide a satisfactory traffic 
bearing seal between the confronting surfaces of adjacent concrete slabs, 
prior such products have not proved to be successful after being in use 
for relatively short periods of time. Traffic driving over the joint 
breaks down the upper, confronting edges of adjacent slabs. The breakdown 
progresses until the joint fails and requires major repairs. Moreover, 
prior such seals have required, more often than not, considerable work on 
the seam between slabs after the slabs have been poured. 
It is object of the invention, therefore, to provide an improved expansion 
joint of the type described, which utilizes a novel cover means for 
covering and protecting the resilient seal, which is interposed between 
adjacent ends of two slabs to allow expansion and contraction thereof. 
Another object of this invention is to provide an improved expansion joint 
cover of the type described which protects the upper edges of adjacent 
slabs at the intersections of the horizontal and vertical end surfaces of 
the slabs, thereby preventing traffic from breaking down such edges. 
A further object of this invention is to provide an improved expansion 
joint cover of the type described which makes use of a number of preformed 
or precast elements, thus minimizing the time and effort required to 
install the cover during roadway formation. 
Other objects of the invention will be apparent hereinafter from the 
specification and from the recital of the appended claims, particularly 
when read in conjunction with the accompanying drawing. 
SUMMARY OF THE INVENTION 
The expansion joint cover is designed to be mounted to overlie a 
conventional, resilient backer rod or seal, which is positioned snugly 
beneath the confronting end surfaces of a pair of adjacent concrete slabs 
of a highway. The upper, confronting edges of the slabs have therein 
longitudinally extending recesses which are right angular in cross 
section. Secured on the job in each such recess by a high density, 
reinforced bedding compound or grout, is an elongate, precast edger strip 
made from a high density, reinforced grout. 
After the edger strips have been grouted in place, a low modulus urethane 
seal is poured over the backer rod. Before the seal sets, an elongate, 
prefabricated cover element, which is generally T-shaped in cross section, 
is positioned over the gap between the adjacent webs so that the opposed 
sides of the cover element project part way into recesses in the upper 
surfaces of the adjacent edger strips, and so that a central web section 
of the cover element extends downwardly into the still molten urethane 
sealing material to become embedded therein when the urethane solidifies. 
The remaining portions of the recesses in the upper surfaces of the edger 
strips, which are not occupied by the cover element, are then filled with 
a low modulus, traffic-bearing urethane.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Referring now to the drawing by numerals of reference, 10 and 11 denote a 
pair of adjacent, concrete slabs, which form part of a conventional 
roadway or highway. These slabs have confronting, spaced, vertical 
surfaces 12 and 13 which in practice extend transversely of the width of 
the roadway, or at least for a given portion of such width. The 
confronting, upper edges of the slabs 10 and 11 have formed therein 
elongate, transversely extending notches or recesses 14 and 15, 
respectively, which are right angular in cross-sectional configuration. 
Each of the recesses 14 and 15 extends for the full width of its 
associated slab 10 or 11. These recesses 14 and 15 are prepared or formed 
at the time that the respective slabs 10 and 11 are poured. 
Secured between the confronting surfaces 12 and 13 of the slabs 10 and 11 
in a slightly compressed form, is an elongate, tubular backer rod or seal 
17, which may be of any conventional design. Normally the outside diameter 
of the rod 17 is larger than that of the space between the confronting 
slab surfaces 12 and 13, so that when the rod is tamped or otherwise 
pressed downwardly between the slabs it is slightly compressed in a radial 
direction, so that it is secured resiliently and snugly between the 
confronting surfaces 12 and 13. Rod 17 is designed to expand or contract 
with the adjacent slabs 10 and 11, thereby to prevent any debris or 
moisture from passing downwardly beneath the rod and into the remaining 
space between the slabs 10 and 11. 
Secured over and protecting the resilient rod 17 is a novel expansion joint 
cover, which is denoted generally in the drawing by the numeral 20. Cover 
20 comprises a pair of elongate, prefabricated edger units or strips 21 
and 22, which are generally rectangular in cross-section, and which have 
in the upper surfaces thereof, as shown in FIG. 1, elongate grooves or 
recesses 23 and 24 which open on the end surfaces 12 and 13, respectively, 
of the slabs. Each of the strips 21 and 22 is designed to be secured in 
one of the recesses 14 and 15 in the slabs by a high density reinforced 
bedding compound or grout 25, and therefore is configured to be slightly 
thinner and narrower than the corresponding recess 14 or 15. During 
assembly the grout 25 is poured into the recesses 14 and 15 to form beds 
for the strips 21 and 22. The prefabricated strips 21 and 22 are then 
positioned in the grout 25 so that their recessed upper surfaces are 
disposed in coplanar relation wit the upper surfaces of the slabs 10 and 
11, and so that their recessed edges are disposed in spaced, confronting 
relation to each other, and in coplanar, vertical registry with the slab 
surfaces 12 and 13, respectively. 
After the edger strips 21 and 22 have been grouted in place, a low modulus 
urethane plastic material is poured into the space between the confronting 
edges of the strips 21 and 22, and on top of the backer rod 17 to form 
thereover, and between the confronting edges of the strips 21 and 22, a 
thick, resilient anchor or seal 28 of plastic material. It will be noted 
that the upper edge of the seal 28 terminates slightly beneath the 
recesses 23 and 24 in the edger strips 21 and 22. 
Secured by the seal 28 across the space between the confronting edges of 
the edger strips 21 and 22 is an elongate, semi-rigid, precast urethane 
cover plate 31, which is generally T-shaped in cross-section. Cover plate 
31 has coplanar, laterally extending flange sections 32, which extend into 
the confronting recesses 23 and 24 in the edger strips 21 and 22, and an 
integral, downwardly projecting web section 33, which is embedded in the 
urethane seal 28. Adjacent its lower edge the web section 33 is widened 
slightly as at 34 to form thereon opposed ribs which prevent withdrawal of 
the web section 33 from the anchor or seal 28. 
It will be noted from the drawing that the flange sections 32 of the cover 
plate 31 project only part way into the registering edger strip recesses 
23 and 24. The remaining portions of these recesses are filled with strips 
36 of a low modulus, traffic bearing urethane material. Each filler strip 
36 is seated upon a very thin layer 37 of a plastic material, which 
extends part way beneath the longitudinal side edge of the adjacent flange 
section 32 of the cover plate 31, and which forms a bond breaker as 
between the edger strips 21, 22 and the cover plate 31. 
In its preferred form the prefabricated cover plate 31 is precast or 
otherwise produced in 4 to 6 foot lengths from a semi-rigid, high modulus 
urethane material, which may be the same type used to produce the grout 
25, e.g., a strong (5000#--24 hrs.--1000#--28 days) reinforced grout. The 
lateral flange sections 32 of the upper, traffic-bearing portion of plate 
31, are designed to cover or overlie from approximately 60-80% of the 
horizontal surfaces formed by the recesses 23 and 24 in the edger strips 
21 and 22. The overall height of the cover 31 from its upper surface to 
the bottom of its web section 33 may be in the vicinity of one inch or 
greater. The various dimensions of the edger strips and cover element may, 
of course, vary depending upon the type of installation. 
From the foregoing it will be apparent that the present invention provides 
a relatively simple and expeditious way to seal the seams between adjacent 
concrete slabs of a highway or the like. The edger strips 21 and 22 and 
the cover plate 31 are prefabricated, so that the only operations required 
to install the cover involve the pouring of the grout beds 25, the 
urethane seal 28 and the strips 36. 
The bond breaker layers or strips 37 permit slight relative movement 
between the cover flange sections 32 and the slabs 10 and 11 as the latter 
expand and contract, and thus prevent the cover 31 from becoming dislodged 
or distorted in response to movement of the slabs. The low modulus filler 
strips 36 can compress and expand, for example in response to movements 
imparted to the edger strips 21, 22 by the slabs 10 and 11, without 
producing any significant disruption in the surface of the highway. Also, 
as shown in the drawing there are spaces or voids 41 formed above the seal 
28 and beneath the flange sections 32 of cover 31 at opposite sides of the 
web section 33 to permit the seal 28 to expand upwardly upon expansion of 
the slabs 10, 11, and without interfering with the vertical position of 
cover 31. 
While this invention has been illustrated and described in connection with 
only certain embodiments thereof, it will be apparent that this invention 
is capable of still further modification, and that this application is 
intended to cover any such modifications as may fall within the scope of 
one skilled in the art or the appended claims.