US1174260A - Pavement. - Google Patents

Description

36-98. 0R 1,174,260 Ex L inside T. F. McGILVRAY.

PAVEMENL APPLlcmu men mm. 12. |913.

f y,- 1,174,260. v Patented Mar. 7,1916.

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THE CGA-IIIA mm CD, "mmm, D' L ROADS 2ND PAVEMENTS 5km/WK T. F. McGILVRAY.

PAVEMENT.

APPLICATION FILED MAH. I2. l9l3.

TMB CCI-Ul Patented Mar. 7,1916.

3 SHEETS-SHEET 2- BIA PIJANDGRAPH C0.. WASIIINDNN, D, c.

nuHLJo ANU f-AVIZMCNIS T. F. McGlLVRAY.

PAVEMENT. APPLICATION msu MAR. 12. ma. 1 1 74,260, Patented Mar. 7, 1916.

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UNTTED sTATEs PATENT oEEIcE.

THOMAS F. MCGILVRAY, OF DULUTI-I, MINNESOTA, ASSIGNOR OF ONE-THIRD TO GEORGE W. BESTOR, 0F MINNEAPOLIS, MINNESOTA, AND ONE-THIRD TO CHARLES GILBERT HAWLEY, OF CHICAGO, ILLINOIS.

PAVEMENT.

Specification of Letters Patent.

Application led March 12, 1913. Serial No. 753,831..

To all ywhom it may concern.'

Be it known that I, THOMAS F. MCGIL- vnAY, a citizen of the United States, and a resident of Duluth, county of St. Louis, and State of Minnesota, have invented certain new and useful Improvements in Pavements, of which the following is a specification.

My invention relates to road surfaces or pavements and has special reference to improvements in concrete pavements for both horse-drawn and motor-driven vehicles.

The object of my invention is to provide a concrete road or street pavement which shall be capable of long withstanding heavy wear, and severe climatic changes; which shall wear evenly, and yet constantly present a gritty, non-slippery surface and thus afford a good foot-hold for predestrians and horses and proper traction for motor vehicles; which shall be absorbent and hence substantially dustless if wetted occasionally; which shall be measurably elastic and therefore adapted to sustain without fracture the traflic loads and temperature changes to which it is subjected; and, which shall be comparatively inexpensive, both as to initial cost and upkeep.

I attain this object in, and my invention comprises, a concrete road pavement composed of a sand-and-cement matrix and an aggregate of gritty absorbent broken sandstone, the matrix and the aggregate being proportioned and sized, as hereinafter described and particularly pointed out in the appended claims.

My invention will be more readily understood by reference to the accompanying drawings, forming part of this specification, and in which:

Figure 1 is a transverse section of a roadway made in accordance with my invention and adapted for the construction of relatively wide pavements; Fig. 2 is an enlarged fragmentary section of the pavement shown in Fig. 1; Fig. 3 is a cross section of a pavement showing the form of my invention as adapted to the construction of pavements which are not extra wide; Fig. 4 is a transverse section of a pavement showing the form of my invention as particularly adapted to the construction of alley or narrow pavements; Fig. 5 is a top plan view of the wearing surface of the pavement illustrating the irregular sandstone areas appearing thereon; and Figs. 6, 7, and 8 are enlarged fragmentary sections particularly illustrating the proportioning of the various sizes of the fragmentary ingredient, as related to the cement matrix.

One of my principal objects is to provide a pavement which will be affected to a minimum extent by the forces which tend to destroy pavements, and which is capable of being built at a minimum cost, which minimum cost depends upon the available material; and another of the underlying ideas involved in my invention is that of providing a wearing surface on the pavement which shall consist principally of many irregular areas of sandstone connected by complementary lines and areas' of combined sand and cement, the sand being combined with the cement in such proportions that the matrix is substantially equal in hardness with the sandstone ingredient so that, as the avement wears away, the wear of the san stone and the matrix is substantially equal.

Another important idea involved in my invention is to provide, beneath the wearing layer, a foundation either of natural material upon which the road is being built or of suitable material provided for the purpose; which shall be porous to a certain extent and thereby permit the draining away of moisture or water, and which shall provide an upper flat surface for receiving the upper layer; in other words, I make the joint between the upper layer and its porous foundation in the form of one or more planes, depending upon the width and particular use of the pavement.

In building a pavement which is extra wide, and in accordance with my invention, and in which the water is drained from the pavement at each edge, I pitch the lower layer toward its edges from the center, making the upper surface of the foundation substantially in two planes which extend upwardly from the curbs and meet along the center line of the pavement. When I build a pavement in this form I provide an expansion joint along the center of the pavement and along each curb, so that the upper layer can expand, contract, or otherwise change its dimensions, in response to changes of temperature, moisture, or other climatic changes without causing disruptive strains in either the upper layer or the foundation.

I have found that I am able, by suitably grading the fragments of sandstone from the larger sizes which I desire to use to the smallest sizes which it is advisable to use, in certain proportions, to provide a pavement in which the rock ingredient can be compacted into a solid mass and retained in such condition by the use of a minimum quantity of cement. And as the cement is much more expensive than rock ingredient, I am thus enabled to construct a pavement at minimum cost. Furthermore, the grading of the fragments according to my invention provides a pavement in which the voids or portions unoccupied by rock fragments are of minimum size and extent. In regions where Pottsdam sandstone or similar material is so expensive that it would be prohibitive to build a pavement principally of this material I make the wearing portion of the upper layer of my pavement principally of Pottsdam sandstone of suitably graded fragments and I support and strengthen this upper portion of the wearing layer by means of an under portion composed chiefly of such material as the region in which the road is being built affords, such as gravel or suitably graded rock fragments. IVhen I build a pavement in this manner the wearing layer itself may be considered as composite, the lower part being made of a low grade material and the upper or wearing surface, substantially about four inches thick being made of the more expensive sandstone material. I however, firmly bind these two into a unitary whole by mea-ns of interlocking binders or fragments. For these binders I prefer to use sandstone fragments, spacing them substantially 18 inches apart over the whole area, and inserting' them into the lower layer before the concrete has set. These binders or pieces of sandstone, at a maximum, measure 5 or 6 inches in length, and I insert them about half way into the lower layer, leaving the upper parts projecting 2g inches to 3 inches above the upper surface thereof. Thereafter when the wearing layer, composed principally of sandstone fragments is laid in position, it not only unites over the whole surface, by means of the cement, to the lower part, but the binder fragments which project into both of the layers firmly bind and unite the two parts into a unitary mass. This composite upper layer is laid upon flat or plane surfaces, as in the form first described, the only difference being that substantially half of it is composed of sandstone fragments instead of the whole.

As stated hereinbefore, the foundation which I prepare upon which to form or support the Wearing layer of the pavement may consist of the natural material, when this is suitable for the purpose, that is, where it is composed of gravel or similar porous ground; but where the natural ground is loam, clay, solid rock or other impervious material I provide a sub-layer or underlayer of broken stone and sand so associated and making the' layer of such a thickness that it serves not only as a foundation for the upper layer, but also to drain away any Water which might be otherwise retained upon the impervious natural foundation.

In cases where the natural material is boggy, or where it may be liable, for some reason, to give way under the load of the pavement and its traffic, I strengthen the pavement by inserting in the lower part of the wearing layer a reinforcement of woven wire. I arrange this woven wire reinforcement about one-third of the thickness of the pavement from its lower surface at which point I have found it to be of greatest bene- Thile as stated herein, the rock ingredient of my novel pavement is preferably Pottsdam sandstone or some similar silicious rock, I prefer at times to use a harder rock, such as granite or Some similar hard rock for the smaller fragments, viz., from 142 or l-l down to i sizes. The smaller fragments of sandstone give way under a less compressive force than the larger fragments, and consequently a pavement in which these smaller fragments of the rock ingredient are of sandstone is not so durable as one in which the smaller fragments are made of the harder rock, but in any case this proportion of harder rock fragments is relatively small, and consequently the pavement as a whole does not present the hard surface which is rovided in a pavement wherein the whole ingredient is made of this hard rock, the effect being rather to increase the life of the pavement and cause it to better withstand the abrasion of constant traiic.

In Fig. 1 I have illustrated a pavement which combines all of the ideas involved in my invention and when building a pavement, as illustrated therein, I first excavate the natural ground until solid ground A is reached and then I refill to the surface B with sand, gravel or broken stone to bring the surface B to the desired level. The pavement illustrated in this figure is shown as being built upon loam, clay, solid rock, or similar substantially impervious material and in this form of my pavement the surface B is sufiiciently below the finished surface of the pavement to permit the providing of a foundation layer C upon which the wearing layer D is to be made. The pavement shown in this figure is adapted for the production of a roadway which is more than thirty feet wide and for such roadways I prefer to make the upper surface of the foundation layer C in two planes C', C', each of which extends from a curb E to the center line of the roadway. The upper surface of the foundation layer C is consequently made up of two planes which are relatively inclined. The pavement is completed by the upper layer D which is divided into two parts D', D', each of which is substantially co-extensive with each of the planes C', C of the lower layer and between the meeting edges of these two portions D of the upper layer, I provide an expansion joint F, and I also provide smaller expansion joints F between the outer edges of the layer D and the curbs E. Consequently when the two parts D of the layer D are eX- panded or contracted in response to climatic changes they can move upon the upper plane surfaces C of the foundation layer without inducing suoli internal strains as would tend to fracture or destroy the upper layer D. In situations where it is impossible to be sure that the ground A will not give way, that is, in boggy ground or in places where the foundation has been tunneled or eX- cavated, I strengthen the pavement by means of a metallic reinforce Gr. This reinforce preferably consists of woven wire of relatively large mesh inserted in the lower part in the upper or wearing layer D. This woven wire extends substantially over the whole area of the layer, but does not enter into or span the expansion Joints between the parts of the pavement. I preferably arrange this reinforcement substantially a third of the thickness of the layer from its lower surface in which position it can best exert its tensile strength to prevent giving away or fracture of the pavement at times when the foundation is not sufficient to support the load. As shown in Fig. 1 the upper layer D of the pavement is a composite layer, that is, it consists of a lower part H and an upper part I. I build the upper layer in this form under conditions where the expense of the sandstone ingredient would be prohibitive, if used for the whole of the upper layer. Under such conditions I make the lower part H of such material as can be best provided from the neighborhood or region in which the road is being built, such as broken stone, other than sandstone, gravel, or other suitable material. I make the upper part I principally of sandstone ingredient and I unite and combine these two parts into one unitary whole by means of binder fragments J which I insert part way into the lower portion H before this portion has set and before the lower portion has finally set I lay the upper part I in place thereon, whereby the upper part I not only cements tightl;7 to the lower part over its whole upper surface but the binder fragments J being embedded in both portions, serve to complete the unification of the two portions into a single unitary wearing layer. The upper surface H of this lower portion H conforms to and with the upper or finished surface of the pavement, and consequently, the upper portion I is of a uniform thickness throughout its extent. In a pavement of this form the rock ingredient of the wearin portions I preferably consists of graded fragments of Pottsdam sandstone, the larger fragments being such as will pass through a 25 screen and be retained upon a 1% screen, the other fragments being graded down to such as will pass through a 1% screen and be' retained upon a l screen. I associate the sandstone fragments with smaller fragments of granite or similar harder rock which smaller fragments are such as will pass-through a l screen and be retained upon a i screen. I preferably use two parts by measure of the larger fragments of sandstone, one part by measure of smaller fragments of sandstone, and of a part by measure of the fragments of harder rock. The stone is thus evenly graded from 25 size down to size, and the larger fragments compose.

substantially sixty per cent. (60%) of the whole and many of them are substantially half the depth of the layer in largest dimension. In preparing the several ingredients for the upper portion of the wearing layer of this composite pavement, I preferably use one part by measure of cement, l parts by measure of sand, and four parts by measure of the broken stone ingredient as specified above. The wearing layer in this pavement is substantially 8 thick and when it is necessary to provide a foundation layer, I prefer to make it at least 5 thick or thicker, depending upon the porosity of the ground upon which the pavement is being laid.

In situations where it is not necessary to make use of the composite wearing layer and in which I make the wearing layer of uniform structure throughout, I use fragments of the sandstone graded in such a manner that the larger pieces thereof are substantially equal to or slightly greater than half of the thickness of the wearing layer of the pavement, that is, in a 8% pavement the larger fragments are about et in their largest dimensions. In a 7 pavement the largest fragments are 3 in largest dimension and in a 5% pavement the largest fragments are 2%, and should it be ,desirable for some reason to make a pavement in which the wearing layer is thicker than 8% the largest fragments would be proportionately larger. I proportion the various fragments in such a manner that the sizes are graded from the largest sandstone fragments to the smallest grain of sand which I use and I have found that the best grading of the fragments is approximately as follows: 60% by measure of the larger size fragments, 20% by measure of fragments which vary from 1i or 1% down to and the remaining 20% graded between the larger sized fragments and these smaller fragments, and, furthermore, I have found it advisable to use the harder rock for the finer fragments, that is, 20% of the ingredient.

In preparing the sand for mixture with the Portland cement, I prefer to grade the sand from that which will ass through a screen down to the very Enest of sand and if sand itself is not available for this purpose, I prefer to use screenings from a rock Crusher, so that the sand will be accurately graded from size down to the fine particles. More accurately I prefer to prepart the coarse stone aggregate for the several thicknesses of pavements which are commonly made as follows:

For the 8% inch pavement: two parts by measure of stone which will pass through a 4% inch screen and be retained on a 3% inch screen; one part of stone which will pass through a 3% inch screen and be retained on a 2% inch screen; one and onefourth parts of stone which will pass through a 2% inch screen and be retained on a 1% inch screen, and one part of stone which will pass through a 1% inch screen and be retained on a inch screen, whereby the stone will be evenly graded from 4% inch size to inch size. This stone graded, as stated, and mixed together intimately into a mass, I term the coarse aggregate for pavement which is 8% thick.

For the 7 inch pavement: two parts by measure of stone which will pass through a 3% inch screen and be retained on a 2% inch screen; one part of stone which will pass through a 2% inch screen and be retained on a 1% inch screen, one-half art of stone which will pass through a 1% inch screen and be retained on a 1inch screen, and three-fourths part of stone which will pass through a 1-inch screen and be retained on a 1,1 inch screen. The stone is thus evenly graded from 3% inch size to inch size. The stone as thus graded and mixed together intimately into a mass I term the coarse aggregate for the 7-inch pavement.

For the 5% inch pavement: two parts by measure of stone which will pass through a 2% inch screen and be retained on a 1% inch screen; three-fourths parts of stone which will pass through a 1% inch screen and be retained on a inch screen; onehalf part of stone which will pass through a inch screen and be retaingd on a inch screen. The stone is thus evenlv graded from 2% inch size to 9; inch size. The stone graded, as stated, and mixed together intimately into a mass, is known as the coarse aggregate for the 5% inch pavement. Under certain circumstances I substitute aharder or tougher or otherwise suitable hard crushed rock for that portion of the graded sandstone aggregate which is of the size of 1% inches and less, but in no case is such substitute rock suicient, either in quantity or size, to materially change the non-slippery, dustless, resilient, absorbent, and even-wearing qualities of the pavement.

In making the concrete for the several thicknesses of pavement, I prefer to use the proportions of sand, cement, and stone, by measure, as follows: 8% inch pavement: cement, 1 part; sand, 1 part; broken stone ingredient, 3 parts. 7-inch pavement: cement, 1 part; sand, 1% parts; broken stone ingredient, 3% parts. 5%-inch pavement: cement, 1 part; sand, 1.6 parts; broken stone ingredient, 4 parts.

Having determined the proportions as above, I make the concrete for the pavement, as follows: First the sand and Portland cement, in the proportions stated for the thickness of pavement proposed to be used, is mixed dry; then the water necessary to make a quaking mortar is added, then the stone aggregate, graded as specified and thoroughly combined together and mixed in the proportions called for, clean and well drenched with water, is added, and the whole mass is turned over in a batch mixer, at least five times, and in all cases a sufficient number of times to thoroughly and completely cover with mortar every particle of stone, and to mix intimately the whole mass. The concrete thus mixed should have a quaking consistency, so that when rammed it will compact within the area of the face of the rammer without being displaced laterally. It is my purpose to provide the materials in such proportions that the concrete shall be as dense as possible, that its, that it shall contain the greatest weight of stone and the least amount of sand and cement in any given quantity and yet be free from voids.

Having excavated down to the solid ground, as hereinbefore stated, and before applying the materials to form the porous foundation C, I first thoroughly roll the surface from which the earth has been excavated to a compact, solid condition and fill in any places where necessary, to make the sub-grade B substantially level from curb to curb. I form thereon the foundation layer C to provide the foundation surface C for the wearing layer D of the pavement. It will be understood that under Some natural conditions, that is, where the pavement is to the laid on clay, loam or solid rock, I excavate down to and prepare the sub-grade as described, but where the ground is composed of sand or gravel, I only excavate down to the foundation level C and prepare the natural material for the reception of the upper layer by rolling or tamping if necessary.

In building a pavement on loam, clay and solid rock, having excavated to the subgrade B, as described, I form the porous foundation or lower layer C as follows: I deposit upon the sub-grade foundation surface B a layer of broken stone, gravel or other suitable material, the fragments c of which vary in size from the largest stone, which will pass through a 3 inch ring down to that which will pass through a -1- inch ring. I carefully proportion the quantities of the several sizes, so that when the layer has been compacted, the voids will be of minimum size, and after the stone has been evenly spread and compacted, I spread upon the surface of the stone sufficient dry, clean, sand to ill the voids between the stone and thereafter tamp or roll the layer, using water for flushing, if necessary, to assist the deposit of the sand in the voids and to campact the layer into a solid condition. I make this layer thus porous so that if any moisture shall pass through the upper or wearing layer, or should otherwise collect beneath the wearing layer, it will not be hindered from freely draining away. Furthermore, the surface C of this layer being composed of this broken stone thoroughly compacted, and the sand filling the voids, is relatively smooth, the compacting of the stone by the rammer tending to adjust the fragments with fiat sides uppermost. I preferably make the upper surface C of this foundation layerC fiat, as shown in the drawing, in the narrower pavements, making it level from curb to curb, in the wide pavements inclined upwardly from the curbs to the center of the street approximating, by the two inclined planes, the curvature of the finished pavement, and in alleys or similar pavements in which it is desired to have a center drain, as illustrated in Fig. 4, I incline the upper surfaces C downwardly from the curbs to the center of the pavement. I make the expansion joint F between the two parts of the pavement and the expansion joints F', and between the or upper layer to correspond with the severity of the traffic it is to stand, and I vary the thickness of the lower or foundation layer in accordance with the thickness of the upper layer and in accordance with the degree of porosity of the sub-grade material. The foundation being porous, serves to drain away any water which may percolate therethrough, and where the natural material upon which it is formed is such that the water will not readily drain out of this foundation layer, I make it of greater thickness to give it a greater draining capacity. As stated hereinbefore, in practice I commonly build three thicknesses of pavement, a thin pavement 5% inches, a medium pavement 7 inches, and a thick pavement 8% inches.

In making pavements, having prepared the concrete of matrix mortar and coarse aggregate for the upper or wearing layer, as hereinbefore explained, I place the concrete immediately upon the foundation, spreading it so as to conform to the crown to be given to the street, which varies with the grade of said street, and of an average thickness to conform to the thickness desired, striking olf its surface with a templet stretched from curb to curb, said templet being cut to the form of the finished surface of the street. I then compact the fragments together by ramming with ahand ram until free mortar appears on the surface. smooth and is substantially the surface of the finished pavement. In ramming the concrete, the pieces or fragments of stone are compacted together in such a manner that substantially all of the fragments which rise to the surface of the pavement present a more or less flat side uppermost, and consequently the pavement presents what may be termed a mosaic surface of irregularly-shaped sandstone areas separated and joined together by the binding material which appears upon a minimum portion of the surface of the pavement. The sand- This surface should obviously be outer edges of the pavement and the curbs, of any suitable material, but I usually emstone surfaces are consequently non-continploy a. material consisting mainly of asphaluous, neither is the intervening binding or 50 tum or some similar semi-elastic substance, cement surface cont1nuous, but as the sand- 115 so that the upper layer D of the pavement stone areas greatly predominate and are escan freely expand and contract without unsentially of a gritty nature, the surface of duly straining any part thereof. the pavement 1s such that the horses can I vary the foundation layer from a minisecure stable foothold thereon and rubber 55 mum thickness, under some conditions of 3 tires cannot skid. 120

inches, to a maximum of 5 inches, dependrl `he highly silicious sandstone which I-asing upon the various conditions under which soc'iate with sand' and binding material in the pavement is being built and is to be building pavements in accordance with my used, and I make the wearing or upper invention absorbs a certain proportion of 60 layer of a thickness which varies from 512` moisture, consequently when the payement 125 inches for light traiiic, that is for a trackhas been sprinkled the moisture whichthe way or suburban roadway, to a maximum sandstone absorbs will be gradually dissiof 8% inches for streets which are designed pated to 4the surface of the pavement and to stand extra heavy teaming. In other will, therefore, retain the dust articles on 5 words, I make the thickness of the wearing the pavement in a moist condition for a 130 relatively long time. The pavement is consequently one which can be maintainedunder ordinary conditions substantially dustless. Furthermore, the sandstone fragments which appear at the surface of the pavement are essentially gritty in their character and provide the pavement with a surface of maximum tractive quality, and as vthe particles of sand in the sandstone are removed or loosened by the traic, the pavement presents a constantly renewed traction surface of maximum efciency.

A pavement made in accordance with my invention is particularly adapted for use upon grades or steep roads or streets where hard stone block', sheet or other homogeneous or concrete pavements could not be used on account of their slippery character. As Pottsdam sandstones are found throughout large areas of the country, it will be understood that my pavement is one which can be constructed at 4a, minimum cost of material.

A peculiar advantage in a pavement constructed in accordance with my invention is that the highly silicious rocks are what may be termed the softer rocks, and these rocks,

when associated in fragmentary form in a pavement, provide a pavement which, as a whole, is elastic to a certain degree, and, being elastic, the pavement Withstands climatic and temperature changes Without becoming fractured or otherwise disintegrated. Furthermore, the sandstone which I associate with the cement in the formation of my pavement is substantially equal in hardness or tractive strength to the cement and consequently the pavement wears down evenly and does not present, after a considerable eriod of wear, the uneven or ridgy sur ace which is presented by pavements built of cement and the harder rocks.

While I have herein` described my avement as being composed of highly sillcious sandstone aggregate associated with sand and cement in certain preferred proportions, it will be understood that other materials as- Copies of 'this patent may be obtained for sociated in different proportions from those mentioned will readily suggest themselves to one skilled in the Yart,'vvhich1vvill approximate the 'result which I obtain, and I therefore do not limit my invention to the specific my invention, I

secure by Letters I being of substantially the same strength as a slab of the same size wholly composed of the matrix.

2. The herein described even-Wearing, non-slippery, absorbent and homogeneous concrete pavement, composed of a sand-andcement matrix and a coarse aggregate of absorbent gritty broken sandstone the largest pieces of which are of substantially the same strength as the matrix.

3. A unit of concrete road pavement, comf. posed of a sand-and-cement matrix and a broken sandstone aggregate, and of substantially the same strength as a unit of the same size Wholly composed of said matrix.

f 4. The herein described unit of concrete composed of graded broken sandstone aggregate and a sand-and-cement matrix, and of substantially the same strength as a unit of the same size wholly composed of said matrix.

. In witness whereof, I have hereunto set my hand this 8th day of March 1913, in the presence of two subscribing witnesses.

THOMAS F. MCGILVRAY. Witnesses: v HENRY S'. SNYDER, PAUL THOMPSON.

ve cents each, by addressing the Commissioner of intents, Washington, D. C.

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