US1960369A - Method of constructing sectional paving and like structures - Google Patents

Description

May 29, 1934. R. C. BosrwlcK METHOD oF ooNsTRUcTlNG sEcTloNAL PAVING AND LIKE STRUCTURES Filed Jan. 31, 193s llchaios Patented May 29, 1934 ,UNITED STATES METHOD F CONSTRUCTING SECTIONAL PAVING AND LIKE STRUCTURES Richard C. Bostwick, Wilmington, Del., assignor to Bond Manufacturing Corporation, Wilmington, Del., a corporation of Delaware Application January 31,

7 Claims.

My invention relates to an improved method of constructing sectional paving and like structures, and has to do, more particularly, with the formation of a more satisfactory expansion joint for such structures than has been capable of attainment by the methods and means heretofore employed. I

In the construction of concrete roads and like structures it has been the practice to form the j structure in spaced sections, with each ofA the intervening spaces or gaps between sections having positioned therein a filler strip or a deposit of ller material which will yield under the compressional strain imposed thereon by the expansion of the sections due to increase in temperature. As a rule, such expansion joints have been constructed of substantially non-compressible plastic material. However, such plastic materials are not materially expansible or comzo pressible, and, if sufficiently fluid to bridge a widened space, the lateral displacement thereof in the widened gap is accompanied by a recession of the surface of the ller material in the gap to a level below the surface of the sections,

thus permitting dirt to accumulate in the gap. Moreover, such filler material, to be effective to bridge a widening gap caused by a decline in temperature, must be plastic at the lowest temperatures to which the structure is subject. 80 Thus. under increased temperatures, the filler material is reduced to a much more fluid state, with the result that, when the sections at each side of the gap expand in accordance with the increase in temperatures and the width of the gap is lessened, a portion of the plastic ller is displaced and flows out above the normal surface of the structure creating an objectionable raised zone or rib at the joint. In the case of sectional highways having such joints it follows that in winter the joints take the form of depressions or open cracks in the road surface, and in summer the joints take the for'm of ribs. As a result, vehicles moving over such roads in summer and winter are subjected to very objectionable vibration and the road itself is subjected to greater wear. The Aonly way in which these conditions may be corrected is by removing the excess or extruded filler material from the road in summer, and refilling the gaps when cold weather has set in. Such periodic attention is in' item of considerable expense. A

It is with these and other difficulties inherent to the plastic joint that attempts have been made to incorporate a certain percentage of fibrous or cellulosic material with the asphaltum 1933, Serial No. 654,504

or other plastic material, rendering it initially partially compressible. As a rule, such materials ultimately lose their compressibility as well as plasticity due, primarily, to the incorporation of road debris therein. As a result, the sectionsl are not permitted to expand freely in accordance with "temperature variations, and heaving and cracking of the sections often occurs.

Theoretically, in-order to provide a satisfactory cork composition joint, it should be necessary merely to make a cork strip having a thickness equal to the width of the space between the sections, and position it in the gap. From the standpoint of actual practice, however, such a.' method and means do not provide satisfactory results. In the case of concrete paving, for example, the sections are laid by casting in situ. This work is seldom done in extremely cold weather, and the sections are therefore not contracted. It is self-apparent then, that a cork strip installed as a gap lling element at the time the structure has been placed in service will, with the advent of colder and drier weather, no longer fill the gap.

With the foregoing in view, it is a primary object of my invention to provide an expansion joint for pavements and like structures which, though employing cork or cork composition as the expansion-contraction-compensating material, will not be subject to loosening, which will not render the surface of l the structure irregular, and will not cause heaving or cracking of the sections due to development of destructive internal stresses therein.

It is an object of my invention to provide an expansion joint for sectional paving and like structures which, once installed, requires no attention and which will not require replacement during`the life of the sections.

It is a further object of my invention to provide an expansion joint and method of making the same which is simple and inexpensive.'

Further objects, and objects relating to details and economies of construction, will definitely 100 appear from the detailed description to follow.

In one instance, I accomplish the objects of my invention by the means and methods set forth in the following specification.` My invention is clearly defined and pointed out `in the appended 105 claims. A structure constituting a preferred embodiment of my invention is illustrated in the accompanying drawing'forming part of this specification, in which `Figure 1 is a. fragmentry view, in

cross-section,

of two sections of concrete paving shortly after initial setting and hardening has taken place and having snugly inserted in the expansion gap provided therebetween, a cork composition ller strip;

Fig. 2 is a similar view, in cross-section, of the same paving sections and cork strip after contraction, due to shrinkage in curing and decline in temperature, has taken place;

Fig. 3 is a similar view, in cross-section, of the same paving sections and cork strip after the metallic ller strips have been driven in place; and

Fig. 4 is a view, in perspective, of the paving sections and expansion joint illustrated in Fig. 3.

The same reference numerals denote Athe same parts throughout the several views.

My invention has to/do with the elimination of certain difliculties incident to the formation of expansion joints in sectional paving such as concrete highways and sidewalks, the sections of which are normally formed in situ by casting upon the road or sidewalk bed, and which are subject to extensive contraction after formation and initial setting, due to normal shrinkage in curing as well as decline in temperature during the succeeding winter season. My invention has for its object the provision of a method and means by which cork composition expansion joints may be installed at the time the pavement is rst constructed, and may, by a single operation, be continued in service for the entire life of the structure.

Referring to the several figures of the accompanying drawing in which I have illustrated a preferred embodiment of my invention, my method consists in the laying of pavement sections 10, 11 upon the bed 13 of the structure,

- at the same time so spacing the adjacent ends thereof as to provide yan expansion gap 12 therebetween which will accomodate thermal expansion of the sections under the higher temperatures to which the structure will be subject. In casting concrete sections in situ upon the pavement bed 13, the usual vcare must betaken to prevent the formation of a web or bridge across the gap which would interfere with free expansion of the sections.' The width of the gap between the adjacent ends of sections will depend, primarily, upon the character of the material of which the sections are formed, the coefcient of linear expansion thereof, the expected maximum variation in temperature, and the length of the sections or spacing between the joints. I have found that, for general purposes and general conditions,`a filler strip 14 of highly resilient cork composition having a length and depth equal to that of the paving sections and a thickness of three-fourths of an inch is very satisfactory. Such a strip as disclosed in my copending application, Serial No. 578,816, filed December 3, 1931, and formed, in anextrusion machine, of approximately two parts, by weight, of comminuted cork and one part of a synthetic resinous binder composed preferably of phenol, paraformaldehyde and diethylene glycol, is capable of compression to nearly one-third its normal thickness, lcompensating for section expansion of close to one-half an inch without permanent impairment of the resiliency of the strip, and without setting up compressive stresses in the pavement sections which would, cause heaving thereof from the pavement bed. In

employing a. filler strip of such compositionv and dimensions in accordance with the present invention it is necessary merely to provide expansion gaps at such intervals and of such width that the linear variation of each section due to temperature increase will not exceed one-half of an inch. The cork strip 14 may be positioned at any time during the construction of the pavement or before the pavement is placed in service. If the weather becomes colder or drier, a certain amount of thermal contraction will take place. Thegap 12 will therefore have widened, as shown in Fig. 2, and the cork strip, by reason of its inherent character, will no longer fill the gap. When this condition has occurred, my invention contemplates the filling of the spaces provided by contraction due to shrinkage and diminished temperature, and also the placing of the cork strip under compression so that, should further contraction take place, it will be automatically compensated by expansion of the cork strip 14. In accordance with my invention the lling of the space provided by contraction may be accomplished in any of several ways. A iine textured concrete may be poured into the space and allowed to set when the contraction has reached its maximum, as in the dead of' winter. Likewise, an asphaltum of low penetration may be heated and poured into the space and allowed to set. It is important, when such material as asphaltum is employed for this purpose, that it be of such character as not to ow at atmospheric temperatures and pressures less than 200 pounds per square inch. The cork strip should be the only element of the joint subject to deformation in accordance with expansion of the sections. Plasticity in the supplemental filler will permit its extension and render the joint objectionable in the same particular characteristic of the plastic joints now in use.v Another method of compensating for contraction after placement of the corck filler strip 14 involved the use of a preformed supplemental strip or strips 15, 16 placed in the gap 12 beside the primary strip 14. Such a strip or strips 15, 16, may be formed of any nonplastic material less compressible than the cork strip 14, preferably, and as illustrated, such strips 15, 16 are formed of metal and are forced or driven into place between the abutting faces of the sections 10, 11 and cork strip 14. I have found copper-nickel alloys, as well as the chrome-steels to be very Well suited as materials for the strips 15, 16 because of their strength and corrosion resistance. If the strips 15, 16 areplaced at a time when the sections are but partiallyv contracted, and the gap 12 may be expected to widen subsequently, it is contemplated to employ strips of such thickness, jointly, as will, when forced into position, -place the cork strip 1-4 under compression, reducing its thickness by an amount equal to or slightly greater than the maximum expected further contraction of the sections 10, 11. In this way, such further contraction as may take place after the strips 15, 16 are placed will be automatically compensated by expansion of the cork strip 14. Moreover, lsuch compression of the strip 14 insures retention of the several strips 14, 15, and 16 in 'the gap 12, by reanson of the frictional contact between these members and with the gap-defining edges of the sections 10, 11. Of course, such supplementalstrips need not extend the full depth of the joint provided they extend sufficiently to keep the joint tight,

Any of a number of substantially non-plastic, non-compressible materials may be employed for 150 the purpose. Even wood, treated to resist decay, might be employed as a material for the strips or shims 15, 16. Likewise, it is not essential that a strip 15, 16 be placedat each side of the cork strip 14. In this connection, I have found a second strip of cork composition, similar to the first 14, having a normal thickness as great or greater than the maximum space expected to be developed between the sections 10, 11 and strip 14, to serve very well. Ifsuch a supplemental cork strip is to be employed, it should first be compressed to substantially 50% its original thickness for a period of time sufficient to effect a temporary and partial paralysis of its resiliency s'o that it may be placed in the space between the strip 14 and sections 10 or 11 before it has recovered its loriginal thickness, This method of installing cork expansion strips is broadly specified and claimed in an application for Letters Patent Serial No. 654,524; filed January 31, 1933, by George P. Edmonds.

I am aware that my invention is susceptible of various other modifications without departure from its scope. I therefore claim my invention broadly as indicated by the appended claims.

What I claim is:

1. The method of constructing sectional paving and like structures comprising: .laying sections of such size and shape as can, within the extremes of temperature to which the structure will be subject, freely expand and 4contract without the development ofdestructive internal stresses, spacing said sections so that a substantial gap is defined therebetween even when the sections are under maximum expansion, forming, of cork or equivalent highly resilient material, a filler strip having a thickness not greaterthan the width of the gapdefined .by said sections at the time of laying, positioning said strip in said gap, allowing said sections to contract after laying, andiI filling the space provided between said strip and the walls of said gap, by contraction of said sections, with material substantially nonplastic and non-compressible at pressures less than 200 pounds per square inch.

2. The method of constructing sectional paving and vlike structures comprising: laying sections of such size and shape as can, within the extremes of temperature to which the structure Will be subject, freely expand and contract without the development of destructive internal stresses, spacing said sections so that a substantial gap is defined therebetween even when the sections are under maximum expansion, forming, of cork or equivalent highly resilient material, a filler strip having a thickness not greater than the Width of the gap defined by said sections at the time of laying, positioning said strip in said gap, allowing said sections to contract in accordance with substantially the lowest temperature to which the structure will be subject in use, and pouring, into the space provided between said strip and the Walls of said gap by contraction of said sections, a setting filler material substantially non-plastic and non-compressible at atmospheric temperatures and pressure less than 200 pounds per square inch.

3. The method of constructing sectionalvpaving and like structures comprising: laying seotions of such size and shape as can, within the extremes of temperature to which the structure will be subject, freely expand and contract Without the development of destructive rinternal stresses, spacing said sections so that a substantial gap is defined therebetween even when the sections are under maximum expansion, forming of cork or equivalent highly resilient material a filler strip having a thickness not greater than the width of the gap defined by said sections at the time of laying, positioning said strip in said gap, allowing said sections to contract in accordance with diminished temperatures to which the structure will be subject ,in use, and positioning in the space provided between said strip and the walls of said gap by contraction of said sections, a second strip of cork havingan instant thickness slightly less than the breadth of said space, said second cork strip having the inherent characteristic of expanding after placement and thereby automatically anchoring itself and said first cork strip in said gap.

4. The method of constructing sectional paving and the like structures comprising: laying sections of such size and shape as can, within the ex` tremes of temperature to which the structure will be subject, freely expand and contract without the development of destructive internal stresses, spacing said sections so that a substantial gap is defined therebetween even when the sections are under maximum expansion, forming of cork or equivalent highly resilient material, aA ller strip having a thickness not greater than the width of the gap defined by said sections at the time of laying, positioning said strip in said gap, allowing said sections to contract in accordance with diminished temperatures to which the structure will be subject in use, and forcing, into the space provided between said strip and the wall of said gap by contraction of said sections, a metallic strip having a length equal to that of said cork strip, and having a thickness tions of such size and shape as can, within the extremes of temperature to which the structure will be subject, freely expand and contract without the development of destructive internal stresses, spacing said sectionsI so that a substantial gap is defined therebetween even when the sections are under maximum expansion, forming of cork or equivalent highly resilient material a filler strip having a thickness equal to the width of the gap defined by said sections at the time of laying, positioning said strip in said gap, allowing said sections to contract in accordance with diminished temperatures to which the structure will be subject in use, and forcing into the space provided between said strip and the walls of said gap by contraction of said sections, a corrosion-resisting metallic strip having a length and depth equal to that of said cork strip, and having a thickness greater than the breadth of said space created by section contraction.

6. The method of constructing sectional paving and like structures comprising: laying sections of such size and shape as can, within the extremes of temperature to which the structure will be subject, freely expand and contract without the development of destructive internal stresses, spacing said sections so that a substan, tial gap is defined therebetween even when the sections are under maximum expansion, forming of cork or equivalent highly resilient material a filler strip'having a thickness equal to the width of the gap defined -by said sections at the gap, allowing said sections to contract in accordance with diminished temperatures to which the structure will be subjectI in use, and forcing into the spaces provided between the abutting faces of the sections and cork strip by section contraction metal strips having a length and depth equal t0 that of the cork strip and having a joint thickness greater than the increase in gap which caused by contraction of said sections.

7. The method of constructing concrete sectional paving and like structures comprising: forming in situ monolithic slab sections of such size and form as can within the extremes of temperature to which the structure will be subject freely expand and contract Without the with said cork strips and having a. joint thickness equal to the maximum contraction of the several sections.

RICHARD C. BOSTWICK.

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