US1960374A - Expansion joint and method of installing it - Google Patents

Description

May 29, 1934. Y Q P EDMONDS 1,960,374

EXPIANSION' JOINT AND METHOD oF INSTALLING 1T Filed Jan. 31, 1935 r/ /J ///I rrr Ej? A Patented' May 29, 1934 EXPANSION JOINT AND METHOD INSTALLING IT George P. Edmonds, Wilmington, Del., assignor to Bond Manufacturing Corporation, Wilmington, Del., a corporation of Delaware Application January 31, 1933, Serial No. 654,524

7 Claims.

My invention relates to an improved method of constructing sectionalpaving and likestructures and has to do, more particularly, with the formation of a more satisfactory expansion joint 5 for such structures than has been capable of attainment by the methods and means heretofore employed.

In the construction of concrete roads and like structures, it has been the practice to form the structure in spaced sections with a filler strip of a deposit of4 filler material in the intervening spaces, the filler being capable of yielding 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 plastic, substantially non-compressible ller material, a portion of which, under the strain of section expansion, is unavoidably extruded from the diminished space between the sections. For instance, in constructing concrete roadways, the space between the adjacent sections is usuallylled with asphalt or a more or less plastic composition consisting of cellulosic material or other inert ller material and a binder of asphaltum. Such fillers are not materially compressible, but are plastic, with the result that, when Vexpansion forces the end walls cf the sections toward each other and the width of the gap -or space therebetween is lessened, a portion of the plastic filler is displaced and iiows out above the normal road surface, lcreating an objectionable raised zone or 4rib at the joint. Frequently, it has been found necessary to go overroads of this character and remove some of the .plastic filler which has been forced out at the joint. Subsequently, when contraction of the road sections occurs due tocolder Weather,the spaces between adjacent sections are-widened, the material in the spaces is insufficient to ll the enlarged gaps, and 40 the material previously extruded from the spaces during Warmer weather, even though allowedto remain on the road surface, does not return to the spaces, with the result that unll'edgaps are created between the sections. Thesev gaps not l only render the road surfa'cerough, but particles of incompressible material gain entry into the gaps in lieu of the original i'lllerand, thereby, practically eliminate the expansion joints. Furthermore, some commonly employed fillers, such 5o as asphalt-impregnated roofing paper and the like, while theoretically capable of being compressed, in practice, because of intermixture with dirt and like non-plastic and non-resilient material, do so only under extreme pressures, with the result that expansion of the sections is often sections, and slip it in place.

accommodated by the heaving thereof from they road bed'and the formation of cracks therein.y

Theoretically, in order to provide a satisfactory cork composition joint, it should be necessary merely to make a cork strip having a thickne equal to the maximum width of the space between From the standpoint of actual practice, however, such a method is extremely difficult if not impossible of execution. In the first place, concrete paving is usually laid in comparatively warm weather, and the sections thereof are not contracted. Moreover, such paving is subject -to linear variation in accordance with its moisture content. xIt is selfapparent then, that a cork strip, installed as the gap filling element, even though initially snugly fitted and cemented in place will, after the advent of colder and drier weather, no longer snugly ll the gap. A yconventional cork composition filler strip-will not ll an expansion gap which has widened since the time the strip was placed. As a result, such a strip becomes loose in the widened-gap.

' It is, accordingly, ajprimary objectof my invention to provide a method of constructing expansion joints employing a cork or cork composition ller strip, which joint will be fully com-` pensating-that is, will permit lthe sections to freely and easily expand to their full extent in accordance with rising temperature, yet which will itself automatically and adequately expand to completely ll the widening gap between sections when they/ are contracting in accordance with declining temperature.

It is an object of my invention to provide a simple, easy and inexpensive method of making permanentv cork-strip expansion joints in sectional paving and like structures, which joints, once installed, require no caulking or further special attention.

It is an object of my invention to provide a cork expansion joint strip for sectional paving and like structures, which strip is inherently selfanchoring.

between pavement sections and preclude the weathering action thereof, and possible formation of ice therein.

Further objects, and objects relating to details and economies of construction and use, will deflnitely appear from the detailed description to 2 s follow. In one instance, I accomplish the objects of my invention by the devices and means set forth in the following specification. My invention is clearly defined and pointed out in the appended claims.

A structure constituting a preferred embodiment of my invention is illustrated in the accompanying drawing forming a part of this specication, in which:

Figure 1 is an end view of the highly resilient cork compositionller strip employed in carrying out of my method, said strip being shown in its normal, uncompressed state;

Fig. 2 is a diagrammatic view of the same filler strip disposed in the press, prior ,to subjecting it to lateral compression;

Fig. 3 is a diagrammatic View ofthe same filler strip and press, said strip being subjected to a compression stress `effecting its reduction to 50% its original thickness;

Fig. 4 is an end view of the same strip immediately after its removal from the .press where it has been subjected to a constant 50% reduction in thickness for a period of approximately twelve hours;

Fig. 5 is a cros -sectional View of the strip shown in Fig. -5 a few minutes after its removal from the press and disposed in the gap between a pair of concrete sidewalk sections; and

Fig. 6 is a similar cross-sectional view of the same. sidewalk sections and illler strip a few hours later, showing the strip expanded into complete lling and self-anchoring relation with the sections.

The same reference numerals refer to the same parts throughout the several views.

In its broader aspect my invention relates to the formation ofl expansion joints in sectional4 vpaving and like construction, such as floors, sidewalks, and highways, and consists first in spacedly laying sections of such size and form that, within the extremes of temperature to which the structure will be subject, expansion and contraction may take place without heaving or cracking of the sections, and second, in preforming, of cork or equivalent highly resilient material, a filler strip for each expansion gap` between adjacent sections, which strip has the characteristic of being temporarily of less thickness than the instant or normal gap between the adjacent sections and of expanding after insertion in the gap, thereby automatically filling the gap, and anchoring itself therein.

More specically, and as applied to Asectional concrete paving construction, my invention consists first in laying concrete sections 10, 11 of the usual form and size, and spacing the sections from each other so that gaps 12 are provided therebetween which will accommodate thermal expansion of the sections under the temperature changes to which the paving will be subject. I n casting the sections in situ upon the pavement bed 13, the usual care must be taken to prevent the formation of a web or bridge across the gap which wouldv interfere with free expansion of the sections. 'Ihe width ofthe gaps will depend, among other factors, upon the character of the material oflwhich the sections are formed, th coefficient of linear expansion thereof, the expected maximum variation in temperature, and the spacing between the joints. I

have found that, for general purposes and general conditions, a ller strip 14 of highlyyresilient cork composition having a thickness of threefourths of an inch is very satisfactory. Such a.

heaving thereof from the bed. In using a filler strip of such composition and dimension, it is necessary merely to provide expansion gaps at such intervals and of such width that, under maximum section contraction, each gap will be slightly less than three-fourths of an inch andl under maximum section expansion each gap will be not less than one-fourth of an inch. General experience with the expected temperature variation and the material of which the sections are made will enable the builder to allow for thermal contraction subsequent to construction. Thus, the proper thickness of the gap form to be used, when casting sectional concrete paving, may be readily computed for any given thickness of filler strip.

Although theoretically the strip 14 may be formed of virgin cork, such cork cannot `readily be obtained in the vdesired size and length, and for reasons of economy and serviceability, I prefer to make the strip of cork composition consisting of comminuted or granulated cork agglomerated with a thermo-setting binder and .formed by moulding in an extrusion machine. A suitable composition which I have found satisfactory for the manufacture of ller strips adapted for use in accordance with my invention consists of 300 pounds of comminuted cork agglomerated with a thermo-setting binder consisting of a phenolic condensation product formed by the reaction of phenol and formaldehyde. This binder sets when heat is applied, for instance, in the extrusion machine, and the resulting composition is compressible but not plastic or displaceable under pressure. As an enduring plasticizing agent, I use, in this mixture, some 60 poundsof diethylene glycol, which also serves as a softening agent for the cork particles 'and renders them more flexible, with the result that the composition is more easily compressible than pure, untreated virgin cork. To this mixture there is added any one of the numerous lubricants used in the cork composition art. The procedure employed in the manufacture of the composition from the above ingredients is preferably as follows: The phenol, formaldehyde and diethylene glycol are mixed and heated in a copper-jacketed kettle. When rthe mixture has ,reached the required temperature, sodium hydroxide is added as a catalyst. The temperature is maintained and heating continued until a sample of the liquid will set, in boiling water, in ten minutes. The reaction is then interrupted, and the intermediate product, which is a heavy liquid, is immediately mixed with the cold ground cork in the proportion ofv about 160 pounds of the liquid to 300 pounds of the cork. These proportions may be varied, however. The mixture thus provided is then taken to the extrusion machine, .ffor instance, such as shown in United States Letters Patent No. 1,453,617, issued May 1, 1923. In such a machine the mixture is confined in a mold at a temperature of about 300 F., which completes the reaction and causes the comminuted cork to be agglomerated by the binder, providing a cohesive mass of the shape desired. 1

Instead of the binder mentioned in the above formula, any one of a number of other thermoerine and ethylene glycol.

setting binding agents may be used for agglomerating'the -brk'particles. As an enduring plasticizing and cork-softening agent. other materials may be employed, among which are glyc- As has been heretofore stated, a suitable strip thickness for general application is three-fourths of an inch. The strip should preferably be as -deep as the thickness of the paving section and should extend the full length of the expansion gap, the upper surface of the strip being iiush with the adjacent sections, and providing therewith, a substantially uninterrupted paving surface. It is obvious, of course, that the gap might, if desired, be filled with two or more strips, superposed, end on end, or side by side, one or all of which may be precompressed. While the strip may have any desired cross-sectional form, for ease of application as well as simplicity of manufacture, I .have found the disclosed rectangular form to be entirely satisfactory.

In accordance with my invention, the cork composition'strip 14 having a normal thickness of three-fourths of an inch is placed in a pressA pressure of approximately 170 pounds per square inch. This pressure and reduction in thickness is maintained for a period ofl approximately twelve hours, whereupon the strip is removed. By means of the prolonged compression of the strip to but its normal volume, upon release the strip will not immediate-ly expand to Vits original normal thickness but will, for some minutes thereafter, recover only some 45%of. its enforced reduction in thickness, as shown in Fig. 4. Thus, the strip will have, for a short period after its removal fromthe press, a thickness of not .materially more than one-half of an inch, and if a gap of some three-fifths of an inch has been provided between the sections, the facile insertion of the strip in the gap, as. illustrated in Iig. 5, is assured. The partial paralysis of resiliency, or self-maintained deformation of the strip is, however, not permanent and usually in the course of less than one hour after its release from the press ,it Will have eX- panded or recovered sufficient of its original nor- .mal thickness to iill the gap and anchor itself itherein by frictional contact with the gap-delining end walls of the sections. `Such a strip, left to expand without restriction, will ultimately recover 95% or more of its original thickness. It is important, therefore, only to be certain that the original thickness of the strip is vsome 5%.

greater than the maximum Width to which the gap between the sections will expand under lowest temperatures. 'ce

mal or original strip thickness. Generally speaking, the rate of recovery, both initial and ultimate is inversely proportional to the length of time compression is maintained. A strip held under compression for two months initially recovered, upon release, but 58% its original thickness. In less than one hour after release, it had recovered more than 60% its original thickness. Some fifteen hours elapsed before it had recovered of its original thickness. In four days it had recovered some, of its original thickness, and after one month it had expanded to approximately its original thickness. The period of compression to 50% original'thickness, is therefore, not critical and may be varied in accordance with requirements. strip of the specified composition maybe subjected to pressures either less or more than 170 pounds per square inch, though not over a broad range comparable, to that relating to the time factor. Cork strips of the composition specified have been subjected to pressures amounting to thousands of pounds per square inch. There are limits, however, beyond which serious and more or less permanent impairment of resiliency results. ,Suiiice it to state that pressures of from l to 150 pounds per square inch effect a substantially uniform progressive reduction in strip thickness; 150 pounds pressure per square inch effecting a reduction in strip thickness to approximately 52% of normal. From 150 to 600 Likewise, a cork l pounds pressure there is eiected a material though increasingly less marked reduction from 50% to 33% The pressure required. to effect greater reduction in `thickness than 50%, as well as the permanent impairment of resiliency resulting from greater compression, render more or less undesirable the practice of my method loylythickness reductions materially greater than 0 o. i v

I am aware that my method may be varied considerably without departing fromthe scope of my. invention. It may be employed in replacing or renewing expansion joints in old structures as well as in the construction of new structures. Other materials such as virginl cork may be used in the fabrication of the filler strip. Moreover, because of irregularity of expansion gap width or unusual seasonalV variations in temperature, a strip of greater thickness than threefourths of an inch may be desirable or necessary. I, therefore, claim my invention broadly as indicated by the appended claims.

What I claim is: l

1. The method of, constructing sectional paving and like structures comprising: laying sections of such size and form as can, within the extremes of temperature to which Fthe 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 orequivalenthighly resilient material, a filler strip having a normal thickness greater than thewidth of the gap defined by the sections under maximum contraction, compressing said strip to such an extent and maintaining said compression for such a period as to'effeet temporary, self-maintained deformation therein characterizedby a reduction in the thickness thereof to less than the normal width of the gap defined by said sections, placing said stripin said gap While still in its temporary,

Y s id strip to expand and fill said gap.

2. The method of constructing sectional paving and like structures comprising: laying 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 development. of destructive internal stresses, spacing said sections so that the width of the gap between the sections under maximum expansion will not be materially less than onethird the width of the gap defined by the sections under maximum contraction, forming, of cork or equivalent highly resilient material, a filler strip having a normal thickness greater than the width of the gap defined by the sections under maximum contraction, compressing said strip to such an extent and maintaining said compression for such a period as to effect temporary, self-maintained deformation therein characterized by a reduction in the thickness thereof to` less than the normal width of the gap defined by said sections, placing said strip in said gap while still in its temporary, self-maintained, deformed state, and allowing said strip to expand and fill said gap.

3. The method of constructing sectional paving and like structures comprising: laying sections of such size and form as can, within the extremes of temperature to Jwhich the structure will be subject, freely expandfand contract without the development of destructive internal stresses, spacing said sections so that the width of the gapbetween the sections under maximum expansion will not be materially less than onethird the width of the gap defined by the sections under maximum contraction, forming, of highly resilient cork composition, a filler strip having `a normal thickness greater than the width of the gap defined by the sections undermaximum contraction, compressing saidcork strip to such an extent and maintaining said compression for such a period as to temporarily paralyze its power of rapid recovery and effect a material though temporary self-maintained reduction in thickness to less than the normal width of the gap defined by the sections, placing said cork strip in said gap whilel still in its reduced state, and allowing said strip to expand and fill said gap.

4. The method of constructing sectional paving and like structures comprising: layng sections of such size and form as can, within the extremes of temperature to which vthe structure will be subject, freely expand and contract without the development of destructive internal stresse spacing said sections so that the width ofthe gap between the sections under maximum expansion will not be materially less than onethird the-width of the gap defined by the sections under maximum contraction, forming, of highly resilient cork composition, a filler strip A having a normal thickness greater than the gap isgreater in width than the reduced thickness of said strip, and allowing said strip to. expand, ll said gap, and anchor itself in placel therein.

5. The method of constructing concrete high- Ways comprising: laying monolithic slab sections having a length such that, within the extremes of temperature to which the highway will besubject, the maximum seasonal variation in length due to thermal expansion and contraction will be not materially greater than one-half of an inch for each section, spacing said sections so' that a gap of at least one-fourth of an inch will be defined between adjacent sections when under maximum expansion, forming, of cork composition compressible to substantially one-third its normal v olume without permanent destruction of its resiliency, a filler strip having a normal width of approximately three-quarters of an inch, compressing said strip to a width of approximately three-eighths of an inch, maintaining said com- .pression for such a period that the resiliency of said strip is temporarily paralyzed and when released and for a short period thereafter, said strip will expand to approximately but threefourths its original normal thickness, releasing said strip from compression at a time when its thickness upon release would be less than the nstant width of said gap, and immediately placing said strip in said gap and allowing'it to expand and anchor itself therein.

6. The method of forming resilient expansion joints in sectional paving and like structures comprising: preforming, of `highly resilient cork composition, a filler strip having a thickness approximately five per cent greater than'the width of the gap defined by the paving sections under maximum contraction, compressing said strip so as to reduce its thickness to substantially fifty per cent its original thickness, maintaining said compression for a sufficient period of time to temporarily paralyze the resiliency of the strip and cause it to initially recover, when released, approximately but fifty per cent of its reduction in thickness, placing said strip in the gap between said sections shortly after it has been released and while its thickness is less than the width of said gap, and allowing said strip to recover as much of its original thickness as is permitted by said sections, thereby filling said gap and anchoring itself therein.

tion in the expansion gap between adjacent sections o f a sectional pavement or similar structure to provide, with said sections, a smooth uninterrupted surface under all actual conditions of section expansion and contraction comprising: a strip of cork composition consisting of highly resilient comminuted cork particles agglomerated with a binder, the corkparticles of which have been highly compressed in one direction and thereby strained to such an extent as to have temporarily lost their characteristic property of rapid recovery to original size'when released, said strip being of slightly less thickness than the width of the expansion gap for which it is adapted, and having the characteristic, if `lexternally unrestricted, of gradually expanding to a thickness of approximately per cent of its initial thickness'whereby wedging or anchorage between the callyv effected by simply laying the strip therein before said expansion has taken place.

GEORGE P. EDMONDS.

paving sections defining the gap may be automati-

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