US3850537A - Pavement construction - Google Patents

Abstract

An improved pavement construction is provided wherein the pavement foundation includes a layer of resilient material to give increased resistance to cracking. As a subcombination, a pavement is disclosed including a layered asphaltic concrete improved by the addition of various scrap or waste materials. This abstract is not to be construed in any way to define or limit the invention set forth below.

Description

United States Patent 11 1 1111 3,850,537 Bynum, Jr. Nov. 26, 1974 [5 PAVEMENT CONSTRUCTION 1,629,487 5/1927 01611116116 404/44 x 2,875,084 2/1959 P tt 404 17 X [76] Invent Dwghs Bynum, 17511 Lormg 3,038,392 6/1962 404144 x LIL, Houston 77040 3,577,893 5/1971 Towner 404/31 3,577,894 5/1971 Emerson, Jr.... 404/31 [22] 1972 3,603,221 9/1971 Barton 1. 404 31 [2]] Appl. No.: 302,422

Primary Examiner-Nile C. Byers, Jr. 52 us. c1. 404 17 Attorney, "1 Ronald Robins; Joe 51 1111.01. E016 11/00 Edwards [58] Field of Search 404/17, 27, 18, 28, 82,

404/31 321 44 57 ABSTRACT 5 References Cited An improved pavement construction is provided UNITED STATES PATENTS wherem the pavement foundation includes a layer of resilient material to give increased resistance to crackroffel 26 3 ing. As a subcombination, a pavement is disclosed in- 622877 411899 ig 'g 4/44 X eluding a layered asphaltic concrete improved by the 6542]6 7/1900 404/72 X addition of various scrap or waste materials. This ab- 656:094 8/1900 De caiimte'r'g"IIII'IIIII'.1.. 260/758 5mm is not to be construed in any Way define or 674,823 5/1901 Amies 106/126 limit the ion set forth below.

1.4] 1,786 4/l922 Hopkinson 404/32 X 1,611,330 12/1926 B1111 404/2s x 5 Clams, 3 D'awmg F'gures Y//// '.o" NF Z2 1 PAVEMENT CONSTRUCTION The present invention relates to pavement constructions, and more specifically to pavement constructions improved by the utilization of normally waste or scrap solid materials. In one embodiment, various waste materials are utilized to provide a resilient layer in pavement foundation to yield improved crack resistance in the foundation. Where the pavememt is utilized as a roadway, or the like, it may include one or more layers of flexible concrete (also called asphaltic concrete or black top), and various improved'flexible concretes are disclosed utilizing normally waste materials for improving the strength, flexibility, elongation and thermal durability of the concrete.

Referring now to the drawings, wherein preferred embodiments of the invention are illustrated, and wherein like numerals illustrate like parts:

FIG. 1 is a view in elevation showing a cross-section of pavement construction, illustrating the various layers including the resilient layer according to one embodiment of the present invention.

FIG. 2 is a plan view of the resilient layer of FIG. 1.

FIG. 3 is a schematic illustration in side elevation of a tire showing how it might be cut to be utilized'in the pavement of FIG. 1.

FIG. 4 is a view in elevation showing a cross-section of pavement utilizing an alternate form of resilient layer. v

FIG. 5 is a perspective view partly in section of a pavement construction utilizing blocks of scrap material in the resilient layer.

FIGS. 6 and 7 are perspective views partly in section of pavement constructions wherein the resilient layers comprise a matrix of the resilient material and a nonresilient material such as sand.

FIG. 8 is an enlarged fragmentary view in sectional elevation of a flexible concrete which may be used in the pavement constructions of FIGS. 1 and 4-7.

A principal problem withpavements and foundations, whether utilized as building foundations or as roadways, sidewalks and the like, is the tendency of the pavement to crack due to movements of the underlying earth. Such earth movements are typically caused by temperature and moisture variations, subsistence, and the like. It has been found that such foundation cracking can be greatly retarded by the use of a layer of resilient material in the foundation between the base and surface layers of the foundation to absorb movement of the base layer without transmitting those movements to the surface layer and to retard the propagation of cracks from one layer to another.

Referring now to FIG. 1, there is shown in crosssection a pavement construction comprising various layers. At the bottom is the grade, or compacted earth, 10 above which is a base layer 12. The base 12-may be of any suitable material such as Portland concrete or' asphaltic (flexible) concrete. Also, the base 12 may be newly laid or may be an old roadway which has been resurfaced. Above the base 12 is a resilient layer 14,

the construction and function of which are described. in greater detail hereinafter. Above the resilient layer 14 is an upper layer 16 also of asphaltic or Portland concrete. A final surface course 18 may also be provided for a very smooth upper surface for the pavement or for waterproofing or the like. The pavement illustrated in FIG. 1 may serve as the pavement for a roadway or sidewalk, or for a building foundation. As discussed, principal problem with such pavements is the-tendency of the pavement to crack due to movements of the earth 10 below the pavement due to changes in temperature, moisture content, subsistence and similar causes. Such movements cause alternate stretching and compression of the overlying pavement. Under such circumstances, cracking of the upper layer 16 may typically result from two causes. First, horizontal movements of the underlying earth cause stretching and/or buckling which eventually cracks the pavernent base 12. Such a crack in the base isillustrated at 20. It is well knownthat such cracks in materialwilltendto propagate through the material upon repeated stresses, untilmovements in the underlying earth, preventing those movements from being transmitted into the upper layers where they would cause defonnation and cracking of the pavement surface.

In the preferred form, the resilient layer 14 comprises an array of tire rings 22 embedded in compactedsand 24. As shown in FIG. 3, the tire rings are provided by cutting the tire around its perimeter perpendicular to the axis. As shown, two cuts are preferably made so that the resulting circular sections or rings will be sufficiently thin to be buried in the sand without necessitating too thick a layer of sand. The center sections of the tires may be ground up for use as an additive to the asphaltic concrete, as described hereinafter. Informing the resilient layer 14, according to FIGS. 1 and 2, a layer of sand is first spread over the base 12 and the tire rings 22 placed in the sand in a grid pattern or'array such as that illustrated in FIG. 2, preferably with-the concave surfaces oriented upwardly as illustrated in FIG. 1. More sand is spread, covering the tires, and the whole layer compacted before the upper pavement layer 16 is poured.

Referring now to FIG. 4, thereis shown an alternate pavement construction wherein the resilient layer is formed of shredded waste metalcans. Thereover the grade or earth 10 is provided the base layer 12 which may be a newly laid base-layer of Portland or asphaltic concrete, or which may be an old'roadway which has cracked or buckled. Over the base: layer 12 is poured a thin coating 26 of bitumen, or other adhesivebinder. A layer of shredded and somewhat compacted metal cans 28 is placed over the adhesive coating 26 to form the resilient layer for the pavement. Another coat of bitumen 26 may be placed on top of the compacted shredded metal cans 28, followed by the upper pavement layer 16.

Another alternate embodiment is illustrated in FIG. 5 wherein the resilient layer 14 is formed from blocks or' cubes 30 of compressed waste material, such as waste paper, which may also include other shredded waste materials, such as rubber, plastic, cloth, etc. The

blocks are formed by application of high pressure on a mold filled with the scrap paper or other waste material. The block holds its shape better if granulated plastic is mixed with the paper and the block is then heated so that the plastic will soften and fuse the paper together. Other binder for the paper or coating for the blocks may of course be used as desired. Although the blocks 30 may be of any desired shape, cubes of approximately 2 inches to a side, or larger, are preferred because of their ease of placement. Where blocks or cubes are utilized as illustrated in FIG. 5, it is also desirable to have layers 26 of bitumen or other adhesive on either side of the resilient layer 14 to bind the cubes to the upper and lower pavement layers 12 and 16.

If desired, the resilient material utilized in the resilient layer 14 may be dispersed in a matrix with nonre silient material such as sand. Such a construction is shown in FIG. 6, wherein the resilient material is arranged in strips 32 alternating with strips of sand 34. FIG. 7 shows the resilient material as an array of islands 36 in a sea of sand 38. Alternatively, the sand could be provided in islands surrounded by a sea of resilient mixture. Numerous resilient materials are suitable for the present invention, but it is preferred to use normally scrap or waste solid material such as shredded tin cans, ground rubber, bark, sawdust or other ground wood.

Where the upper pavement layer 16, or, if provided, the surface course 18, is of flexible or asphaltic concrete, commonly referred to as black top, it has been found that the concrete can be improved by the incorporation of various types of waste solid matter. For

The use of ground rubber in the asphalt mix also improves the flexible concrete by making it more resilient. The rubber may be conveniently obtained by grinding or shredding scrap tires. One percent or more by weight of rubber is effective in improving the pavement and up to 50 percent by weight may be used.

When making asphaltic concrete, dirty aggregate, such as gravel, is washed and dried before mixing with the asphalt or other binder so that good adhesion between the binder and the aggregate is achieved. If good adhesion is not obtained and the concrete is being used as an outdoor surface course, then water will seep around the rocks and cause deterioration of the binder. However, at the same time, poor adhesion of the binder to the rock will result in greater elongation capability in the asphaltic concrete and make it less liable to cracking. Therefore, an asphaltic concrete utilizing a usually asphalt or tar, mixed with various sizes of crushed rock or gravel aggregate. It has been found that this type of flexible concrete can be improved by the substitution of crushed or ground glass for part or all of the usual rock aggregate. The glass can be obtained from scrap glass containers, crushed in a jaw crusher or ground in a ball mill. The use of crushed glass results in more long splinters or slivers of glass which give the asphalt increased skid resistance. The greater the proportion of glass substituted for the usual rock aggregate, the greater the resistance of the concrete to thermal distress. Flexible concrete formulated with glass shows less expansion and contraction due to temperature changes, than does conventional flexible concrete.

According to another aspect of the present invention, lab tests have indicated the desirability of plastic additives in the flexible concrete to improve the adhesion and cohesion. The addition of thermoplastic material to the mixture would also tend to decrease chemical aging of the asphaltic concrete due to cross-linking with the asphalt. Thermoplastic materials are utilized since they deform or melt upon heating. Thennal plastic waste materials, such as plastic bottles or the like, may be shredded or ground and added to the hot asphalt or hot aggregate prior to or during the mixing of the two to form the concrete. The heat of the asphalt or aggregate will melt the plastic and the mixing of the concrete disperse the plastic throughout the mixture. Thermoplastic material may be effective in an amount as small as 0.1 percent by weight based on the entire weight of the concrete mixture, and may be used in any amount up to about 10 percent by weight.

dirty or a coated aggregate will yield superior pavement if protected with a thin waterproof layer, or if the quality of the binder is improved as by adding of the scrap thermoplastic material as described above.

An asphaltic concrete utilizing a dirty or coated aggregate is illustrated in FIG. 8. There the aggregate particles 40 have a surface coating 42 of some material such as dirt which does not adhere tightly to the aggregate. The binder or asphalt 44 is therefore prevented from adhering tightly to the aggregate, permitting the aggregate to move slightly in the binder so that the concrete can expand or flex to a greater extent without the formation of cracks. The coating 42 need not be continous, however, and may be discontinuous at spots such as at 46, permitting the binder to adhere to the aggregate sufficiently to hold the concrete together.

While the aggregrate coating 42 may simply be dirt adherring to the aggregate, it may also be a synthetic coating deposited on clean aggregate such as clean rock or gravel, or the crushed glass described above. One such coating material which has been found satisfactory is pulp paper. The paper may be scrap or new, and may be added to the aggregate by mixing the paper pulp with the aggregate, or by dropping the aggregate through pulp and then allowing the aggregate to dry.

Another synthetic coating for the aggregate may be latex rubber derived from any suitable source. The rubber may be mixed with the hot aggregate to coat it prior to mixture of the aggregate with the asphalt or other binder.

Reinforcement of asphaltic concrete has been recognized as desirable, but is too expensive to utilize in general practice. However, it has been discovered that reinforcement of the asphaltic concrete by the addition of grass or animal manure, will greatly improve both the strength and elongation characteristics of the concrete. FIG. 8 shows such fibers 48 in the concrete.

A fiber-reinforced asphaltic concrete according to the invention may comprise approximately 3% to 12 percent by weight asphalt, or other binder material, and approximately 0.1 to 15 percent by weight of f1- brous reinforcing material, with the remainder comprising aggregate such as crushed rock, gravel, ground glass, etc. A portion or all of the aggregate may be coated as above described.

It is apparent that other asphaltic concretes may be provided by a plurality or all of the above features, that is, where shredded tires and scrap plastic are added to the asphalt binder, together with scrap rags, manure, straw, hay, etc., and wherein the concrete aggregate is crushed or ground glass. The sublayers of the overall pavement might also utilize scrap tires, tin cans, waste paper, etc. as indicated above. The use of such paving constructions would result not only in improved pavements, but also would greatly reduce the problem of solid waste disposal.

The foregoing disclosure and description of the invention are illustrative and explanatory thereof and various changes in the size, shape and materials, as well as in the details of the illustrated construction, may be made within the scope of the appended claims without departing from the spirit of the invention.

What is claimed is:

1. In a pavement construction of the type including upper and lower layers of concrete, the improvement comprising: 7

an intermediate layer, disposed between said upper and lower layers, said intermediate layer being formed of a matrix of rubber tire rings embedded in sand.

2. The pavement according to claim 1 wherein said tire rings are formed from whole tires cut about their perimeters perpendicular to their axes to form a plurality of annular sections.

3. The pavement according to claim 1 wherein said tire rings are disposed in said sand with their concave surfaces oriented upwardly.

4. A pavement comprising,

upper and lower layers of concrete with an intermediate layer of shredded metal cans. 5. The pavement of claim 4 wherein said metal cans are held in place with an adhesive binder.

Claims (5)

1. IN A PAVEMENT CONSTRUCTION OF THE TYPE INCLUDING UPPER AND LOWER LAYERS OF CONCRETE, THE IMPROVEMENT COMPRISING: AN INTERMEDIATE LAYER, DISPOSED BETWEEN SAID UPPER AND LOWER LAYERS, SAID INTERMEDIATE LAYER BEING FORMED OF A MATRIX OF RUBBER TIRE RINGS EMBEDDED IN SAND.

2. The pavement according to claim 1 wherein said tire rings are formed from whole tires cut about their perimeters perpendicular to their axes to form a plurality of annular sections.

3. The pavement according to claim 1 wherein said tire rings are disposed in said sand with their concave surfaces oriented upwardly.

4. A pavement comprising, upper and lower layers of concrete with an intermediate layer of shredded metal cans.

5. The pavement of claim 4 wherein said metal cans are held in place with an adhesive binder.

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