US797408A - Pavement. - Google Patents

Description

No. 797,408. PATENTED AUG. 15, 1905. G. W. (K; W. T. S. CRIGHPIELD. PAVEMENT.

APPLICATION FILED DEC. 20. 1904.

WITNESSES. INVENTORS AUORI/E C'TATES PATENT OFFICE.

GEORGE W. URIUHFIELD, OF JERSEY OlTY, NEW JERSEY, AND \VILLIAM T. S. CltliUHFlELD, OF NEW YORK, N. Y; SAID GEORGE W. lRlCHFlEliD ASSIGNOR TO SAID WILLIAM T. S. ORlOHFlELD.

WAVEMENT.

Specification of Letters Patent.

Patented Aug. 15, 1905.

Application filed December 20, 1904.. Serial No. 237,669.

./'0 all whom it may concern:

Be it known that we, GEORGE W. CRICH- FIELD, a resident of Jersey City, in the county of Hudson and State of New Jersey, and VII.- LIAM T. S. Ciuc'nirmnn, a resident of the city of New York, borough of Manhattan, in the county of New York and State of New York, citizens of the United States, have invented a new and Improved Pavement, of which the following is a full, clear, and exact description.

The invention has for its object to provide an improved sheet or so-called monolithic pavement; and it relates to that general class in which the pavement is formed of bituminous or asphaltic mixtures.

Sheet-asphalt pavements as usually constructed are formed of a base or binder laid. in a continuous sheet and having above it a wearing-surface formed of a mixture having greater elasticity than the base or hinder. Such pavements involve a great number of difficulties and disadvantages. Among these may be stated the fact that the material of which these sheet asphalt pavements are formed must be laid hot, and great expense and inconvenience are involved in transporting the hot material to the point at which the pavement is to be formed, and also injury is done to the material from overheating; the pavement cannot be properly laid in extremely cold or stormy weather; a large body of skilled labor is required to lay the pavement, and a relatively slight fault on the part of any one may easily result in seriousinjury to the pavement; it is impossible to effect a true or thorough connection between the base or binder and the wearing-surface, resulting in the creeping of the wearing-surface and in consequent Lmevenness of the pavement, and repairs can he made in the pavement only at serious inconvenience both to traliic and to the operator. These difficulties render it almost impossible for smaller cities, towns, and villagcs to employ the asphalt pavement as ordinarily laid. in overcoming these and other disadvantages of the common practice we pro vide a pavement formed of a number of separate blocks of convenient size and of a peculiar composition, to be hereinafter set forth. Each ofthese blocks comprises abase or bind er of firm rigid composition and a Wearing-surface of a high degree of elasticity thoroughly and inseparably joined to the base, so as to form of the two layers a solid single block. These blocks are laid together on a suitable bed, and they are in a peculiar manner, to be hereinafter explained, so effectually bound together as to form a continuous, unbroken, and practically monolithic or sheet pavement.

Reference is to be had to the accompanying drawing, illustrating a pavement embodying the features of our invention, which drawing represents a sectional view of the pavement.

in said drawing, A indicates a bed on which the pavement is laid; B, the blocks, each comprising a base 6 and wearing-surfaces Z2 inseparably joined together, and C indicates the bond between the blocks, firmly connecting them and forming said blocks into a truly continuous or monolithic paved surface.

The bed A may be of any material desired; but it is preferably concrete or other equivalent material, which will furnish a rigid substructure or support for the paving. The blocks B may be of various sizes. For ordinary work the dimensions twelve inches by five inches to twelve inches by three to four inches are preferable.

The base or hinder of the paving-block is of such composition as to give it a high degree of rigidity, strength, and weight. It is composed of a granular mineral aggregation or mixture and a bitumen. It is necessary to form the base or hinder as nearly solid as possible, so as to attain rigidity and strength. Looking to this end, therefore, we prefer to form the base 5 of the block B of the following substances and in the following manner: Trap rock, granite, or other hard stone is crushed into particles from tln'ee-quarters of an inch or one inch in diameter down through. all grades and sizes to an impalpable powder. This rock forms the base of the composition, and the purpose in crushing .it through all grades and sizes from three-quarters of an inch or one inch lumps to an impalpable powder is to enable the mass to be solidly packed together, the liner particles filling the interstices between the larger particles, thus giving great weight and solidity for bulk. if desired to render the mixture of still greater density, filling all voids between the particles, sand of various degrees of fineness, carbonate of lime, and Portland cement may oe, all or severally, added to the mixture, thus forming a mineral aggregate which may be packed with almost absolute density and which will furnish the required strength and rigidity. This aggregate is mixed in an ordinary asphalt-mixing machine, or in any other suitable way, with a quantity of pure bitumen, which is preferably nine per cent. of the aggregate. To effect this mixture, the aggregate should be first heated to about 250 Fahrenheit, and the asphaltic cement or bitumen, tempered with a fiux according to the desired practice, should be mixed with the aggregate at a temperature preferably not exceeding 300 Fahrenheit. The composition therefore formed of the above-described mineral aggregate and the asphaltic cement or bitumen brought together by heat is allowed to set or harden to form the finished product under certain peculiar conditions, however, which will hereinafter fully appear.

The wearing-surface or top layer of the paving-block is formed with a peculiar composition which insures elasticity and toughness. This is preferably a properly balanced or proportioned mixture of coarse and fine sand free from loam, salt, quicksand, silt, organic matter, or other substance deleteriously affected by the elements and not containing a marked excess of lime. The sand should be hard and should be of such a degree of fineness that all of it will pass a ten-mesh screen, (figuring meshes per inch,) about five to eight per cent. should pass a twenty-mesh screen, twenty to thirty-five per cent. should pass a fifty-mesh screen, ten to twenty per cent. a one-hundred-mesh screen, and at least a small percentage should pass a two-hundredmesh screen. In this manner a dense compact body is assured, since the finer particles fill in the interstices between the larger particles. If desired, in order to increase the density or compactness of this mass, ten per cent. to fifteen per cent. of an impalpable mineral dust may be added-for instance, carbonate of lime, marble-dust, or sand-and to still further increase the density two per cent. or three per cent. of Portland cement passing a four-thousand-mesh screen may be added to the aggregate, increasing its compactness without increasing its bulk. The mineral aggregate thus carefully graded should then be incorporated with an asphaltic cement. This cement should be selected with great care. We prefer to use none but a pure natural lake asphalt free from soluble salt, free sulfur, organic matter, glance-pitch, ironpitch, silt, loam, or other impurities, this asphalt being softened by a flux of pure maltha or liquid asphalt, showing a test of 9 to 15 Baume. The asphaltic cement composed of these elements thoroughly incorporated the one within the other in such proportions as their respective natural consistencies may demand is then mixed with the mineral aggregate previously described at a temperature of from 250 to 300 Fahrenheit. This composition forming the elastic wearing-surface of the pavement preferably contains from eleven to thirteen per cent. of pure bitumen, the amount depending somewhat upon the nature of the asphalt used as the base and its sensitiveness to heat. The nature of the composition of which the wearing-surface is formed enables us to employ nearly twice as much bitumen as that which is contained in ordinary or commonly-used asphalt blocks, thus adding to that extent to the strength, elasticity, and durability of the pavement.

The two compositions respectively forming the base and wearing-surface of the pavement being now mixed and heated, as described, should be separately conveyed to their respective molds, which molds are of the size and form similar to that of the paving-block to be formed. These molds should then be superimposed, so that the two compositions yet in plastic form he together one above the other. The compositions should now be subjected to extreme pressure tending to force the two layers together, and notwithstanding the differences in the materials of which the two compositions are formed the asphaltic cement embodied in each will cause the two compositions when forced together to adhere firmly and inseparably,forming a solid block, the only division in which being that afforded to the eye by reason of the different materials with which the two compositions are formed. After sufficient pressure has been applied and the mass hardened sufiicientl y the finished pavingblock should be removed from the molds. This block combines, therefore, in one inseparable mass a semirigid base or binder and a tough elastic wearing or top surface. It is here pertinent to observe that the union thus efiected between the base and the wearingsurface of the paving-block is absolutely perfect, and consequently far superior to that which is effected between the two layers in an ordinary asphaltic pavement, and the blocks may be transported indefinite distances much the same as granite blocks, brick, wooden blocks, or the like.

In laying the blocks to form the finished pavement a suitable bed should be provided, as indicated in the drawing, and the blocks are laid on the same in any desired arrangement, the base 6 of the block bearing on the bed A and the wearing-surface b uppermost. After the blocks have been laid the joints between them are filled and the blocks thoroughly welded or joined together by a mixture of hot asphaltic cement and Portland cement in proportions of about forty parts of asphaltic cement to sixty parts of Portland cement. This hot mixture poured into the joints is caused to adhere or weld itself to the pavingblocks, particularly the wearing layers 6 thereof, by passing a hot instrument over the joints.

rezaee it i This instrument is preferably the ordinary hot smoothing-iron employed in laying asphalt pavements. The result is the production of a pavement of perfect composition, the upper and lower layers, or, in other words, the wearing-surfaee and base, of which are inseparably joined and the upper surface of which is continuous and unbroken, forming a true sheet or monolithic pavement. The elastic wearingsurface of this pavement absorbs the concussion of traffic and distributes the same first to the semirigid base or binder and through this to the concrete bed on which the pavementis laid. In this manner the weight and jar of the traffic are absorbed and distributed upon the solid bed A, which is of such formation as to safely bear the load imposed.

Having thus described the preferred manner of carrying out our invention, what we claim as new, and desire to secure by Letters Patent, is the following:

1. A pavement formed of separate compact blocks of granular mineral material and a bituminous material laid together edge to edge and homogeneously joined to each other by a bond formed of bitumen and a pulverulent mineral whereby the bond is given essentially the hardness and consistency oil. the blocks and a continuous sheet or monolithic pavement produced.

2. A pavement formed of separate compact blocks of granular mineral material and bituminous material laid together edge to edge and homogeneously joined by a bond containing bitumen and Portland cement, whereby to produce a continuous sheet or monolithic surface.

3. Apavementformed of separate, compact blocks, each made up of two layers or strata permanently joined and of such variation in composition as to make the upper stratum or wearing-surface elastic relatively to the lower stratum or base, said blocks being laid together edge to edge and homogeneously joined by a bond containing material contained in the blocks, whereby to form a continuous sheet or monolithic pavement with a relatively rigid base and a relatively elastic wearingsurface.

at. A pavement formed of separate compact blocks, each made up of two layers or strata, permanently joined together and composed of granular mineral material and bituminous material of such form and quality as to make the upper stratum or wearing-surface elastic relatively to the lower stratum or base, said blocks being laid together edge to edge and homogeneously joined by a bond containing bitumen, whereby to produce a continuous sheet or true monolithic pavement with a relatively rigid base and a relatively elastic wearing-surface.

5. A pavement formed of separate compact blocks laid together edge to edge, each block being composed of a relatively elastic top or wearing layer and a relatively rigid bottom or base layer and said blocks being welded together by a bonding material having an affinity to the material or materials of which the blocks are formed whereby to produce a true or perfect bond between the blocks and a continuous sheet or monolithic pavement with an elastic wearing-Snriface and rigid base.

6. A paving-block tli'ori'ned of two layers or strata permanently or inse 'iarably joined together by pressure when in hot plastic condition, each stratum containing granular mineral material and bituminous material and the composition of the layers being varied sufficiently to make the top or bottom layer relatively elastic and the bottom or base layer relatively rigid.

7 A paving-block formed of two strata or layers permanently or inseparably joined together by pressure when in hot plastic condition, each stratum containing granular mineral material of varying degrees of lineness and bituminous material and the composition of the layers being varied sufliciently to make the top or wearing layer relatively elastic and the bottom or base layer relatively rigid.

Iln testimony whereof we have signed our names to this specification in the presence of two subscribing witnesses.

GEORGE W. CRICHF .ELD. l VlLLlAh l 71.. URIL {Fl ELI).

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