US1573923A - Pavement and process of making - Google Patents

Description

Feb. 23', 192e. T 1; s73,923

H. E. FLETCHER 4- PAVEMENT AND PROCESS 0F, MAKING v' Ax-*iled'rvfawh 28, 1923 lNvENTOR ATTORNEY Patented Feb. 23, 192e.

PATENT OFFICE.

HERBERT E. FLETCHER, 0F WESTFORD, MASSACHUSETTS.

PAVEMENT AND PROCESS OF MAKING.

Application filed March 28, 1923.

To all whom t may concern:

Be it known that I, HERBERT E. FLETCHER, a citizen of the United States, residing at llestford, in the county of Middlesex and State of Massachusetts, have invented certain new and useful Improvements in Pavements and Processes of Making, of which the following is a specification.

This invention relates to roads and the process of building them. y

-In the art of building what are considered permanent roads, it is necessary to so build that water shall not get in joints, cracks,` or other places in the `road proper' where it can freeze-and thus cause breakage, and so far as possible to keep it out from' underneath where freezing and thawing would have a tendency to heave and break the road.

Roads of this character as now constructed include a subbase, generallyv of a natural soil, eitherv excavated to the desired depth and shape, or filled, and the load carrying top.

`It has been found highly desirable that the top should be continuous to keep out the water as above described, and that this top `or pavement should have sufficient beam ,strength to span any soft spots in the subgrade which have arisen from any cause.

@ne great difficulty encountered has been `the uneven expansion and contraction on account of heat and cold which goes on 1f the roadbed is reinforced with metal ties, and which also goes on in most structures which are not monolithic. Y

I am aware that roads have been built with a base. of concrete or other similar monolithic material, and that on this has been placed a cushion of sand or cement, and that upon such cushion or upon the concrete itself, a surface layer of granite blocks, bricks, `or other material has been placed.

In roads so constructed, however, the different layers expand or contract to different degrees and after a time cease to be bound together but allow a certain amount of slippage.

In such a case, if there are two layers each four inches thick, the combined strength is very much less than one monolithic. structure eight inches thick.

It is thepurpose of my invention to provide an homogeneous structure with a very durable topV wearing surface and one in which the expansion and contraction will be reduced to a minimum, and Ywhat there is will do little, if any, harm.

Serial No. 628,382.

Another purpose of my invention is to reduce the cost of such structures by constructing such a monolithic roadbed of such beam strength and consistency that less material can be used while still obtaining the desired strength.

Another object of my invention is to utilize the irregular blocks which are now waste in stone quarries, particularly, granite quarries, and blocks of various depths.

Suitable blocks for my pavement can be manufactured cheaply from what is now thrown away as useless except for crushing.

My invention further consists in an improved method of bonding stone blocks, which form the top part and which are of uneven depth, with the concrete bottom to provide a monolithic slab or a pavement of the required strength. This is accomplished by alternating .deep and shallow stone blocks either alternate. stone blocks in each course or in alternate courses or by any arrangement by which adjoining blocks vary in depth sutliciently to effectually bond the stone blocks with the concrete. By this method, stone blocks of either regular or irregular shape, but of various depths can be used. The results obtained are a reduction ot` labor and waste in the manufacture of stone blocks to be used in accordance with this method, and the increased strength of the pavement, one of the large items in the cost of stone blocks to be laid by usual methods being the expenditure of labor and waste of material necessary to manufacture stone blocks of uniform depth.

My invention further consists in animproved method of thoroughly uniting the several parts of the structure into a solid slab pavement by the sequence of operations as hereinafter described so that all parts of my pavement are bonded into a monolithic structure which will not be injured by ex pansion and contraction from heat and cold.

In the drawings,

Figure l is a cross section of a pavement of my construction and the surrounding earth.

Fig. 2 is a cross section of diagrammatic form and in part perspective showing some of the modifications which I may use.

F ig. 3 is a plan view of such a pavement as shown in Fig. l.

In the drawings, A represents the natural earth which should be excavated to form a subg-rade or foundation, the lines of which the finished surface of the street.

On this subgrade or foundation, I spreadl a mixture B made of broken stone, gravel or other aggregate, preferably of relatively small size such as might pass through a one inch ring, mixed dry with Portland cement and sand. A. good mixture is one part'Portland cement, three parts'sand and six parts broken stone by volume.

The aggregate may be damp when used, but should be free from excess water. l

The mixture should be thoroughly blended in a mechanical mixer, preferably of the batch type, until it is of uniform color and composition. No water is to 'be added before or during the mixing. i

After mixingit is spread on the subgrade to the desired depth and kept dry until the stones or pavingblocks have been properly set and rammed into place. rlhis mixture B should be covered` with the surfacing blocks-very soon after it is laid before there is any chance for it to harden on account of Vmoisture from the earth or afir. i

For mypreferred type of pavement shown in Fig. 2, I use paving blocks H and K of substantially box shape and rectangular top faces, but of varying depths, the blocks H being deeper than the blocks K.

These are, preferably, laid in courses, suchk Y blocks are packed to a full compact bed in the mixture, which is then a dry cushion. Blocks should not be laid to any great extent in advance of the rammiiig.

After being laid, they are rammed to make a smooth or relatively smooth surface, and any which project unduly or are far below the general surface are removed and replaced by others. v

These blocks must be so bedded that they will stand up in the bottom mixture preferably witli sufficient strength so that workmen can pass over them with rammers.

Up to this stage of the process, the blocks must be kept perfectly clean, free from dirt, clay, and other objectionable materials, and the joints are to be kept open down to the point where the bottom mixture penetrates.

Vith substantially regular blocks such as shown in Fig. 2, the dry bottom B does not come up to any great'extent into the joints 34, but where more irregular blocks are used,

mixed in a mechanical mixeror grouting machine, and of sufficient fluidity to allow it to run thoroughly into the jointsvand down clean to the bottom B.

This grout should be applied in suoli manner that the joint' openings are `completely filled and the excess grout appears onthe Y surface of the blocks. It should be broomed or scraped intothe joint openings if necessary so as to fill them. It may be necessary to repeat this grouting until the joint openings are permanently filled and the grout no longer settles therein. 'I`he surface of the pavement thus grouted should immediately be broomed to an even smooth surface. i

After the grout has been applied and vany excess removed, the pavement kshould be completely covered with a blanket, which may be of sand, which must be kept moist .for perhaps a week. The pavement shouldV be protected from all travel for perhaps ten days, during ywhich time the moisture inthe subgrade through capillary attraction works up into the bottom part B of the pavement,

gradually causing it to take itspermanent set.V e l Inl Figs. l and 3, I show a foundationin the soil A indicated by 40, 41, 42; The dry bottom mixture B is the same, but as the blockseM and O are of dierent depths and of more irregular shape, thedry bottom mixture B works up into the joints t4 to a higher point than where the blocks are rectangular.

rIhe construction is the same as Where rectangular blocks are used, and the joints 44:

' are filledY with a suitable grout L as described above. j

I may form a concrete curb such as E integral with the botto-m B, or I may use a` In the constructionl shown in Fig. l, if granite blocks M, O are used, as the granite is stronger than the concrete the fact that it is narrow at the bottom andwider at the top gives a wide or thick section of concrete and a narrow section of granite which adds tothe strength.

As there is no separate layer or base of a material even slightly dierent from the wearing or load carrying surface, expansion and contraction by heat Aand cold have no effect on my structure as it is a monolithic and thoroughly bonded slab. It expands and contacts so that there is no tendency to crack.

Instead of using a preferably dry mixfor my base B, I may use a damp mix. I find, however, that if a. wet mix of the usual concrete type is used, it is impossible to level the facing blocks because when one is rammed down, another jumps up.

I claim:

1. A monolithic pavement, the bottom of which is formed of aggregate, sand and,

hydraulic cement and water, and the top -of which is formed of stone blocks having substantially smooth top surfaces and which extend into the bottom to depths varying substantially whereby the top and bottom are bonded together into a monolithic slab, the spaces between the blocks up to their top faces being filled with a grout of sand,

Y cement and water.

2. A monolithic pavement the bottom of which is formed of aggregate, sand and hydraulic cement and water, and the top of which is formed of alternately deep and shallow stone blocks which extend into the bottom to various depths whereby the top and bottom are bonded together into a monolithic slab, the spaces between the blocks up to their top faces being filled.

3. A monolithic pavement, the bottom of which is formed of aggregate, sand, hydraulic cement and water, and the top Aof which is formed of stone blocks which extend into the bottom to depths varying substantially whereby the top and bottom are bonded together into a monolithic slab, the spaces between the blocks up to their top faces being filled.

4. The process of making monolithic pavements, which consists of depositing on a foundation vof compact earth, a thoroughly mixed dry concrete composed of aggregate, sand and hydraulic cement, then imbedding therein paving blocks of various depthsso that the dry concrete will fill the spaces beneath the shallow blocks between the deep blocks, then ramming or rolling' the blocks to bring their top faces to an even surface, then sprinkling the mass with suiiicient water to cause the initial set to the hydraulic cement, then while the mass is still wet, filling the spaces between the blocks with a grout composed of hydraulic cement, sand and water.

5. The process of making monolithic pavements which consists of depositing on a foundation of natural soil a dry concrete composed of crushed stone, sand and hydraulic cement thoroughly mixed, then imbedding therein while the concrete is still dry, paving blocks of sufficiently irregular depths to thoroughly bond together the dry concrete and the blocks, then ramming or rolling the blocks to bring their top faces to an even surface, then sprinkling the mass with suflicient water to cause the initial setto the cement, then while the mass is still wet, filling the spaces between the blocks with a grout composed of hydraulic cement, sand and water and then allowing sufficient time for the concrete to take its substantially permanent set from water obtained from the natural soil foundation by capillary attraction, before tratiic is allowed.

(i. A monolithic pavement, the bottom of which is formed of aggregate, sand and hydraulic cement and water, and the top of which is formed of stone blocks, certain of said blocks being relatively deep and the others relatively shallow, said blocks being arranged to form a smooth top and a relatively shallow block being arranged adjacent a relatively deep block so that the top and bottom are bonded together into a monolithic slab, the spaces between the blocks up to their top faces being filled with a grout of sand, cement and water.

7. rIhe process of making monolithic pavements which consists of depositing on the natural soil a bottom part of aggregate, sand and hydraulic cement thoroughly and evenly mixed when dry, and of then embedding therein stone blocks of which a substantial part are of different depths from the other part so that the dry mixture will work up between them, and they will stand up, then ramming the blocks to bring their top surfaces to substantially an even level, then moistening the top of themix, and then filling the remaining spaces between the blocks to the top thereof.

8. In a pavement, the combination with the natural soil on which it rests, of a monolithic slab of which the bottom part is formed of a mixture of aggregate, sand and hydraulic cement mixed when dry to a uniform consistency throughout, and the surface is formed of stone blocks a substantial part of which are of substantially different depths from the other part, such blocks being embedded in the bottom mixture when dry so that it extends up between them, and a certain amount of moisture, together with a filling which extends substantially up to the top faces of the blocks.

HERBERT E. FLETCHER.

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