US1747125A - Road and street construction - Google Patents

Description

Feb 1l, 1930- G. F. MUPHY 1,747,125

ROAD AND STREET CONSTRUCTION Filed June 6, 1928 .,L. c@ Z4 INVENTOR Patented Feb. l1, 1930 PATENT; OFFICE GUY F. MURPHY, 0F CORAL GABLES, FLORIDA ROAD AND STREET CONSTRUCTION Application. led June `6,v

This invention relates to a road construction.

An ob] ect of the invention is the provision of a road and street constructiomand a proc-v eSs of forming the same, in which bituminous rock is crushed so that it will pass through a sieve of predetermined mesh and then rolled cold on a proper foundation of a road bed to form a base or levelling course, after which the ground bituminous rock is applied as a Wearing surface.

A further object of the invention is the provision of a road and street construction and method of forming the same in'vvhich crushed bituminous rock, or a mixture of bituminous rock and clean hard stone, granite, or slag is mixed with the bituminous rock to form a levelling course after Which the wearing surface is formed of ground bituminous rock rolled cold upon the levelling surface. f

This invention will bebest understood from a consideration. of the following detailed description in connection with the accompanying drawings; nevertheless, it is to be understood thatthe invention is not confined A Referring more particularly to the draw-d ings 10 and 11 designate a pair of concrete shoulders running longitudinally and located at the side edges of the road. Intermediate these shoulders is formed a base 12 which may consist of crushed rock, concrete or any suitable material of predetermined depth and rolled to form a compact foundation.

Located upon the top of the base or foundation 12 is a layer 13 formed of crush bitu- 1928. Serial No. 283,419.

minous rock of a predetermined depth which is siutable for the needs which is known as a levelling surface. A Wearing surface is shown at 14, and is formed of ground bituminous rock and rolled While cold.

Referring more particularly to Fig. 2, a base 20 is formed of any suitable material and is rolled to provide a compact foundation. Upon this base is rolled, While cold, a levelling surface 21, which is formed of equal partsl of ground bituminous rock and clean, hard stone, granite or slag. The material forming the levelling surface must pass through a one inch mesh sieve, or screen.

Rolled upon the levelling surface 21 is a 65 surface 22 known as the wearing surface and formed of ground bituminous rock. l

Referring more particularly to Fig. 3, it will be found that the base andthe levelling surface have been combined into a unitary structure, as indicated at 30, and formed of bituminous'rock, .which has been crushed to pass through a two and one-half inch mesh screen. A Wearing surface 31 is applied to the top of the base 30 and consists of ground 75 rolled bituminous rock which is ground in order to provide for a finetexture of material.

All materials are applied by the cold process and are laid just as the materials come from-the producer, no artificial heat being applied for the purpose. f

The levelling course indicated at 13 in Fi 1 consists of crushed bituminous rock whic has been .passed through aone inch mesh screen and must be freeof any foreign matter. The asphalt content of the bituminous rock of this course should average not less than three (3) per cent or more thansix and one-half (6l/2) per cent loss by ignition when determined by the olhcial ignition method. The thickness of this course when compressed should not be less than approximately one inch nor more than oneand one-half inches. However, the thickness of the course depends upon the type of traffic which the road is designed to serve. The bituminous rock may be spread or levelled off manually` or with a blade, or by means of the usual grader. When thecrushed bituminous rock is raked ofl;1 by hand, it is dumped in piles and shovelled into the levelling course, the materials are deposited in piles and then shovelled into position after which the grader is run over the surface until a uniform thickness is had throughout the surface. During the raking of the materials, it is necessary that 'the workman keep off the raked surface in orderV to prevent a non-uniformity of the coating.

After a suiicient amount of surface of the proper thickness of the loose materials has been raked to allow for rolling, a self-propelled roller, which may be atandem, or the three wheel type, weighing approximately five to eight tons is operated over the surface. In any event, the roller must be equipped with snugly fitting ashy pans and provided with Scrapers for maintaining the wheels clean.

In order to attain the uniformity of thick,- ness of the levelling surface, it is necessary zo to operate ythe roller along lines which are e parallel to the center-line of the road bed, beginning with the outer edge of the road bed and gradually working towards the center of the road, each succeeding strip of rolled material being overlapped with the preceding rolled strip of levelling surfacefor approximately one-third the Width. This rolling operation in the manner just described, should be continued until the surface has been'throughly bonded and compacted.

Where certain g portions of the road bed show uneven surfaces, the roller may again be applied, but moved at an angle of forty-five degrees lor diagonally across the street from each side. The surface is now ready for the application of the Wearing surface. The materials from which the wearing` surface formed consists of finely ground bituminous rock whichshould meet the following requlrem'ents. First: The materials must be free of all foreign matter. Second: The asphalt content of the rock should be such that when tested accordingto the official ignition method,`the representative sample should lose not less *than six and one-half per cent. Third: The materials should be `capable of passing through a screen one inch 90%, threequarter inch 80%, one-half -inch 7 0%. The thickness of the wearing surface should be not less than one-half in ch and not more lthan one and onehalf inches, the thickness, of course, depending upon the type of traffic it will have to serve.

This ground bituminous rock is located in piles and -shovelled into place in such a manner that'each succeeding shovel full should be deposited in close association with the preceding, while the thickness of the materials in the loose state should be considerably higher `than the required thickness of the loose materials, in order to enable the materials to be raked to the proper grade. The raking operation follows immediately the shovelling of. the materials onto the levelling surface. Care is taken that the materials are uniformly distributed over the road bed. After the materials have been raked in position, care must be taken that no traliic is permittedof any lrindon the loose materials.

If the materials forming the wearing surface are dry, andthe atmospheric temperature is approximately fifty degrees F., or above rolling may be proceeded with immediately as fast as suiicient amount of materials are eyenly applied to the levelling surface to enable the roller to operate. lVhere the tem- 'peratu're is below fifty degrees F. and the atface on the levelling surface, the `surface of the levelling course must be cleaned so that it will be free of dust or any foreign material, f

and furthermore, the surface of the levelling course shouldbe free of moisture.

Where an old base or surface that is substantial is used, and is smooth, an asphalt primer or paint should be applied before the levelling course has been'laid. This improved method of bituminous rock construction may be used for heavy traiiic on streets or highways" and may be employed to surface brick, concrete, asphalt or wooden block surfaces. In the application of the materials shown in Fig. 2, a slightly different procedure is required, due to the diiferencein the nature of the materials employed. The levelling course in this construction is composed of equal parts of bituminous rock used in the wearing surface, and any hard aggregate such as slag, lime stone, or granite. In this case the hard aggregate must. be free of foreign matter and dust and of a size to pass a one inch mesh.

sieve. Equal parts of the sla-g, lime stone, or granite and bituminous rock, should be mixed together in any appropriate manner such as by hand, or by means of a revolving or. concrete mixer. After the ground bituminous rock, and the mineral aggregate have been thoroughly mixed, they are applied to the base I of the road bedin the same manner as has been explainedin reference to the application of the-bituminous rockfor forming the levelling course. The top coat or-wearing'surface is formed of ground bituminous rock applied in the manner described for the'application of A the Wearing surface ofthe road bed shown in Fig.- 1.

The road bed shown in Fig. 3 has a base formed rof crushed bituminous rock and a wearing surface of ground bituminous rock thus eliminating the foundation orfbase ,indicated respectively at 12 and 20 in Figs. 1 and 2. However, the base member indicated 15 at 30 in Fig. 3, Vconsists of large particles of the crushedbituminous rock and they are of such size thatthe particles'will pass through a two and one-half inch mesh screen. The test for the as halt content should not average 2f) less than tliiree nor more than six and onehalf per cent loss by ignition when deterc mined by the oicial ignition method -by mleans ofja representative sample of rock asalt.- P In this case, as in all, other cases, the bitu minous rock should be free of all foreign materials and moisture. After the subgrade 'is prepared, this rock shall be placed and spread to a depth of "not over four inches in a loose 3o state at one spreading. A ten ton, three wheel roller is employed for compacting the rock and the rolling operation should start along the edges and working towards the center. Two complete rollings over the surface should be suicient for' the purpose. After the rolling operation has been completed a second layeris spread over the first compact 'layer' and thoroughly rolled. The top wearing surface formed of ground bituminous rock is "40 then applied in `the manner previously described. J

I claim .Y A road rconstruction comprising a base formed of a cold rolled layer of crushed rock, 1s a cold rolled layer or levelling course on the crushed rock and formed of crushed bituminous rock which will pass through a one inch mesh screen and having an`asphalt content of not 4less than three per cent or not more 5o thanvsix and one-half per cent loss by ignition when determined by the oicial ignition method, and a top layer of cold rolled ground bituminous rock which seventy per cent will pass through a one-half inch mesh screen. 'GUY F. BTURPHY.

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