US3474581A - Thermally expansible concrete slab and method of forming same - Google Patents

Description

Oct. 28,1969 P. M. GERY I 3,474,581"

THERMALLY EXPANSIBLE CONCRETE SLAB AND METHOD OF FORMING SAME- Filed Nov. 16. 19s? 4 2 Sheets-Sheet i Oct.28, 1969 P.M.GERY v 3,474,581

THERXALLY ZXBANSIBLE QONCRETE SLAB AND METHOD OF FORMING SAME Filed Nov. 16, 1967 2 Sheets-Sheet 2 United States Patent 3,474,581 THERMALLY EXPANSIBLE CONCRETE SLAB AND METHOD OF FORMING SAME Pierre M. Gery, 19 Avenue Danielle Casanova, St. Gratien, Val-dOise, France Filed Nov. 16, 1967, Ser. No. 683,687 Claims priority, application France, Nov. 18, 1966,

Int. Cl. E04b 5/429, 1/92; E01c 3/06 US. Cl. 52-220 Claims ABSTRACT OF THE DISCLOSURE This invention relates to a new type of slab, more specifically, concrete slabs, which may have a very large continuous surface and which may be subjected to major temperature variations without risk of cracking.

Concrete slabs, with or without reinforcement, have been made for a long time. However, the moment we want to increase the surface of these slabs, we quickly run into a cracking phenomenon, caused, on the one hand, by the shrinkage of the concrete, and, on the other hand, by temperature variations.

Although we cannot eliminate this shrinkage, we can nevertheless reduce its effects by means of continuous casting without interruption or resumption of casting and by making a wise choice with respect to the quality of the cement (coarsely-ground cement, which has been allowed to settle or age in the tank or silo), as well as by means of a suitable choice of the additives on the basis of their mineralogical composition, their quality, and their grain size.

On the other hand, as regards temperature variations, it is obvious that we are powerless with respect to the effects of dilatation: These are the elongations or shortening effects which result from this.

In addition to the inconveniences coming from the discontinuities on the surface due to cracks, the latter constitute the source of further cracks, since the water that has penetrated into these cracks acts like a jack when it freezes.

The object of this invention thus involves a new type of slab which may have the shape of a large surface on the order of several thousand square meters and which is capable of taking the effects of shrinkage and temperature variations without risk of cracking.

According to this invention-instead of putting the slab either on the foundation itself, without anchoring, or on foundations having a more or less large number of anchoring pointswe create a single line of fixed points, preferably along a middle line in the slab, a line from which the dilatations or expansions can take place quite freely because the slab simply slides on a supporting or carrier slab, through the action of a material with a low friction coefiicient.

The main object of this invention thus consists in a new concrete slab, particularly for landing strips, bridges, and skating rinks, characterized by the fact that it features a line of abutment from which the upper portion of the slab, hereafter called the upper slab, can expand by sliding on a sliding surface that rests on the lower portion, called the carrier slab.

In this way we get a new type of slab which can be used particularly as a slab for covering pipes intended to permit the formation of ice on skating rinks and capable of resisting, for example, temperature fluctuations varying between 10 and +50 C., as slabs constituting the highway top of a bridge and especially as the top for bridges that will be heated for the purposes of eliminating the ice forming on the top, or as a takeoff and landing strip, for example.

Other characteristics and advantages of this invention will emerge in the course of the following specifications which are given here with reference to the attached drawing that shows one version of the new type of slab, by way of example.

In the drawing we have the following:

FIGURE 1 is a diagram of a plan view of a slab, constructed in accordance with the teachings of this invention.

FIGURE 2 shows the section AA indicated in FIG- URE 1.

FIGURE 3 is a detail of section AA at the junction of the coating or covering slab and the' carrier slab.

FIGURE 4 is a section through the slab along the plane B-B, indicated in FIGURE 1.

FIGURE 5 is an elevation view of the support of the cooling pipes.

FIGURE 6 is a diagram of a plan view of a ring-shaped slab.

FIGURE 7 shows a vertical section through a bridge, according to this invention.

At point 1, in FIGURE 1, we have a schematic plan view of a slab. By way of example and in order to facilitate the description here, we will assume that we want to make a continuous slab which will be m. long and 30 m. wide, a slab which is supposed to contain pipes to be used for cooling the slab so as to support a blanket of ice for a skating rink.

According to the invention, the covering slab 1 is kept fixed in position along the hatched portion 2 whose section is visible along cross section AA which we can find in FIGURE 2; this hatched portion here constitutes the abutment.

On this figure, the number 3 refers to the carrier slab. Steel rods, put down in advance, such as those at 4, strengthen the connection between section 2 of covering slab 1 which is cast in the depression or dug-out portion provided for in section 5 of carrier slab 3. The slabs 1 and 3 can slide with respect to each other by means of an intermediate material 6 which is shown in detail in FIG- URE 3.

According to our invention here, covering slab 1 and carrier slab 3 are separated from each other by means of two superposed layers or blankets 7 and 8 consisting of plastic materials; the faces of these two sheets that are in contact with each other must have the smallest friction co-efficient possible. They might preferably be made up of sheets of plastic-like materials which are placed end to end. We want to make sure here that the edges 10 of two adjacent sheets of one and the same layer will not coincide with the edges of two contiguous sheets of the other layer.

On the other hand, in order to avoid the penetration of the cement between the two plastic sheets, we cover upper layer 8 with a bituminized paper 9, such as tar paper.

The plastic friction coeflicient on plastic is something like 0.08 and this permits the free dilatation of the cover ing slab from the abutment. For obvious reasons of symmetry, this abutment is placed along one of the axes of symmetry of the slab, so that we can thus preserve a symmetry of expansions and contractions. In our case here, the abutment is located along the smaller axis of symmetry and the concrete is poured from there, con,

tinuously, by two teams, starting in two opposite directions.

In the particular example selected for the purpose of facilitating these specifications, pipes 11, in FIGURE 4, are used for cooling and have been arranged in the longitudinal direction along the slab and they are consequently perpendicular to the line of abutment.

In order not to overcrowd the figure, we illustrated one of the supports of pipes 11 in FIGURE 5. These supports consist of a central bar 12 featuring round-offs 13 for the placement of the pipes as well as stands 14, each made up of two oblique posts so as to make the support stable. The lower ends of these posts are curved back so as not to pierce; and damage the tar paper and, of course, the plastic.

This arrangement is particularly advantageous because it gives us one complete and active section of concrete.

In addition, the slab 1 has an upper and lower layer in the form of two squares or square patterns of reinforcing mesh of x 10 cm. The lower layer, consisting of steel rods 15 and 16, is located a short distance from carrier slab 3, in other words, at most 2 cm. from the carrier slab in the example considered here. The upper layer consists of steel rods 17, which rest directly on the pipes 11, and of perpendicular steel rods 18. This arrangement makes it possible to reduce the thickness of the concrete between pipes 11 and the surface of the slab. In any straight section, the sum of reinforcement areas found is on the order of 1% of that of the concrete section.

FIGURE 6 shows a slab 19 in the form of a ring. This slab, which is based on this invention, as we can see, has a fixed middle portion represented by the hatched areas 20 and 21. We have also shown here a rectangular slab of the same type, 22, likewise featuring a fixed area 23, which is aligned with 20 and 21. By way of example, the straightline portions of slab 19 are on the order of 110 m. and the radius of the outside circle is 35 m. This slab can thus expand freely from areas 20 and 21. The concrete is poured continuously, as in the case of a rectangular slab, with two teams starting from each of the abutments found at 20 and 21 and going in opposite directions so as to meet along the major axis of the slab.

We might also start with one carrier slab and line up the dug-out areas at 20 and 23 so as to make up slabs 19 and 22. However, between slabs 19 and 22, we must have at least one sliding joint or seam so as to guarantee their free movement because of the differences in expansion of each of these slabs.

Another particularly interesting application of this invention concerns structures such as bridges. We know that bridges across rivers have a tendency to become iced during cold weather and this defect is remedied by heating the highway.

We can solve the problem of deformations and cracks due to expansion by laying the highway support down in the form of an upper slab which, depending upon the type of heating, can be a covering slab. However, instead of laying out the abutment along the minor axis, we preferably select the major axis as shown in FIGURE 7. The upper slab 24 is attached to the lower slab along the abutment situated along the central axis of the bridge. Slab 24 rests on slab 25 by means of sheets 26 which have a small friction coeflicient and the expansions can thus take place without any damage on either side of the abutment. It is clear that slab 25 rests on columns or posts 27 either directly or by means of the conventional structures used here.

Although this invention has been described here so far only with reference to one possible version, it is obvious that numerous additions, deletions, or substitutions could be made in connection with the new slab shown here. Thus the fixed portion of the slab could be staggered with respect to the axis and, in certain special cases, it might even be inclined with respect to the axes of symmetry. Similarly, the sliding materials could be something other than plastic. The bituminous sheet itself could be replaced with some other material or it might even be eliminated entirely depending upon the nature of the sliding material.

What is claimed is:

1. A concrete slab assembly comprising:

(a) a lower carrier slab having a line of abutment defined therein and a substantially planar upper surface adjacent the line of abutment,

(b) an upper slab having a substantially planar lower surface overlying the carrier slab and anchored thereto along the line of abutment such that the upper and carrier slabs do not move relative to each other along the line of abutment, and

(c) means intermediate the planar surfaces of the upper and carrier slabs to permit sliding movement therebetween in response to temperature induced expansion and contraction.

2. A concrete slab as defined in claim 1 wherein the abutment comprises a dug-out portion in the carrier slab and further comprising reinforcing rods imbedded in the abutment for securely anchoring the upper and carrier slabs together.

3. A concrete slab as defined in claim 1 further comprising fluid conduits within the upper slab for carrying heating or refrigerating fluids.

4. A concrete slab as defined in claim 3 further comprising a first pattern of perpendicular reinforcing rods adjacent the lower planar surface of the upper slab and a second pattern of perpendicular reinforcing rods adjacent the fluid conduits.

5. A concrete slab as defined in claim 4 further comprising metal support members for the fluid conduits within the upper slab, the support members having roundedoif feet in contact with the intermediate means.

6. A concrete slab as defined in claim 1 wherein the means recited in sub-paragraph (0) comprises two superposed sheets of plastic.

7. A concrete slab as defined in claim 6 further comprising a sheet of tar paper between the lower planar surface of the upper slab and the uppermost sheet of plastic.

8. A concrete slab as defined in claim 1 wherein the upper slab constitutes the road surface of a bridge and the line of abutment coincides with the longitudinal axis of the bridge.

9. A method of forming a concrete slab assembly having a lower carrier slab with a line of abutment defined therein and a substantially planar upper surface adjacent the line of abutment, an upper slab having a substantially planar lower surface overlying the carrier slab and anchored thereto along the line of abutment, and means intermediate the planar surfaces of the upper and carrier slabs to permit sliding movement therebetween in response to temperature induced expansion and contraction, comprising the steps of:

(a) initiating the pouring of the concrete for the upper slab at both sides of the line of abutment simultaneously, and

(b) continuously pouring the concrete thereafter out to the extremities of the slab.

10. A concrete slab assembly comprising:

(a) a lower carrier slab having a line of abutment defined therein and a substantially planar upper surface adjacent the line of abutment,

(b) an upper slab having a substantially planar lower surface overlying the carrier slab and anchored thereto along the line of abutment, the upper and ldwer slabs being symmetrical about one or more axes of symmetry and the line of abutment being located along one of the axes of symmetry of the slab assembly, and

(0) means intermediate the planar surfaces of the upper and carrier slabs to permit sliding movement therebetween in response to temperature induced expansion and contraction.

References Cited UNITED STATES PATENTS 1,934,266 11/1933 Hession 52573 2,590,685 3/1952 Coflf 55573 X 2,910,921 11/1959 Freyssinet 948 6 2,997,770 8/1961 Beltz 52220 X 3,000,276 9/1961 Foulger 9410 FRANK L. ABBOTT, Primary Examiner P. I. FAW JR., Assistant Examiner US. Cl. X.R.

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