US423796A - District of co - Google Patents

Description

(No Model.)

- E. F. MURDOCK. METHOD 0F FORMING CONCRETE PAVEMENTS.`

' Patented Marpl, 1890.

ETERS. humming-.19mm washing. D4 l;

UNITED STATES [PATENT EEICE.

ED'WIN F. MUEDooK, or WASHINGTON, DIs'rEIo'r oF COLUMBIA.

METHOD OF FORIVIING CONCRETE PAVEMENTS.

SPECIFICATION formingpart of Letters-Patent N o. 423,796, dated March 18, 1890. Application tiled July lil, 1889.' Serial No. 317,122. (No specimens.)

exact description, reference being had to the accompanying drawings.

This invention relates to improvements in the method of forming concrete pavements, and has for its objects to prevent the cracking, sliding, and rotting of the wearing-course.

To these ends the invention consists in forming in the course contiguous to the wearingcourse indentations, into which the material .of the wearing-course may iow when spread'.

In the drawings, Figure lis a plan View of a street prepared with a hydraulic cement concrete base provided with elongated grooves in two series. Fig. 2 is a sectional view of the same, showing in position the strips used in forming the grooves. Fig. 3 isa sectional view of the pavement complete.

In this class of pavements the thermal changes produce in the wearing-course an eX- pansion and contraction. These actions cause i in the pavement-s as at present constructed a movement of the wearing-surface on the base. As the material forming the wearing-course is laid while hot, and therefore fully expanded, the contraction is quite considera-ble, and as the ductility of the material is small the pavement is pulled apart in cracks. This contractile force operates along the diameters of the pavement from curb to curb and end to end. In thus operating' along the length of the pavement the force generated is greater than that generated from curb to curb, and whenthe pavement breaks it is across the length. If these cracks become numerous and the distance between any two of them is less than the distance between the curb, the

crack takes place in a line with the length of the pavement. Along the ,edgesfof'V these cracks thema-terialdisintegrates and rots,

.andrin'as'hort time forms a hole which has to be repaired at an additional cost.

It is to prevent the movement of the wearing-surface on the base that I provide the grooves A A and B B. The former extend across the street and the latter in the direc tion of the street. These grooves I form in the base as it is being laid by placing in the upper` surface while it is soft strips ofwood. As the base is tamped down, the strips are 1 driven downwith it and left in the base while it is setting.

of a pick under the ends and raising them, or by any other suitable means. When they are thus taken out, the base is provided with a number of grooves in two series', the one eX- the street.

In placing the strips the ends should lap, asshown in Fig. l of the drawings, in order to leave nocontinuous line unbroken in either direction. -No particular care is necessary. to be used in placing the strips. I place them at about ten feet apart and in about the order shown in Fig. l of the drawings, though any other order will answer the purpose. In

street,especially at intersections, Where the strain is exerted" in all directions; but as a general rule I prefer the design shown in the drawings. The strips may be of any desired thickness and length. That shown in the drawings is one inch thick and eight feet long. After the strips are taken out of the base, as described, the wearing-course is spread upon it, flowing into the grooves A and B, as shown in Fig. 3. When thus spread, it is rolled hard, driving the material in the grooves solid.

contract, the strain is resisted every ten feet by the sides of the' grooves A and B, with which the said wearing-course is engaged. By thus taking up the strainat short intervals the multiplying of the force above referred to is prevented, and as the tensile strength of the wearing-course is greater than the contractile force generated atthese intervals the breakipr isobviated.

lengthwise of the street, are provided to prevent the rolling of the wearing-surface to- Ward the gutter. This is caused by the softening-of the Wearing-conrseandin this condition sliding on the base down the grade of the street to the gutter. By preventing the sliding on the base, as is done by the grooves, this action is prevented, and the Wearingtending across and the other lengthwise ofi `some instances I lay them obliqu ely across the When it has thoroughly set., theV pieces may be taken out by placing the ledge When, now, the Wearing-course commences to Theseries/of grooves B, which are placed IOO tending across the lines of the contractile' strains, and spreading upon thevsaid base thus prepared a bituminous concrete Wearingcourse in a plastic condition adapted to iiow into the said grooves, substantially as dcscribed.

2. The method of forming concrete pavements, which consists in laying a hydraulic concrete base, forming grooves and indentations therein-while in aplastic condition, and

spreading` upon the said base thus prepared a bituminous concrete Wearing-coursejin aplastic condition adapted vto iiow into the said grooves and indentations, substantially as described.

3. The method of forming concret-e pave,- ments, which consists in laying a hydraulic concrete base, placing in the upper surface of the said base While-in a plastic condition strips of wood or other suitable ,material` eX- tracting the said strips When the base has partly set to form grooves in the upper surface, and spreading,` on the base thus prepared a bituminoils concrete Wearing-course in a plastic condition adapted p to flow into the grooves thus formed, substantially `as de-V scribed.

\ p EDWIN F. MURDOCK.

Vitnesses: ,y

JAMES M. DURANT,

ALEX. S. STEUART.

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