US1701497A - Paving - Google Patents

Description

Feb. 12, 1929. 1,701,497

R. c. HEATH PAVING H Filed J an 27, 925

WI TNESSES IN VEN TOR:

TTORNEYS.

Patented F eb.. 12, 1929.

PATENT FHQE.

RALPH C. HEATH, OF MELROSE, MASSACHUSETTS, ASSIGNOR TO THE BARBER AS- PHALT COMPANY, OF PHILADELPHIA, PENNSYLVANIA, A CORRQRATION OF WEST VIRGINIA.

ravine.

Application filed January 27. 1925. Serial No. 5,008.

My invention relates to paving and pavements, and particularly pavements with a bituminous top layer or wearing surface. I aim to construct a serviceable, durable pavement or roadway in a simple, convenient, and economical way. In suitable forms of embodiment, such as that hereinafter described, myinvention makes it possible to construct a good bituminous-topped pavement on aconcrete base with a minimum of equipment, and out of ordinary materials such as are usually available along or near the right of way,without stonecrushers or crushed stone for the concrete, or heating and hot-mixing apparatus for the bituminous topping. The materials can be used wet, which minimizes interference and delay from rainy weather.

Thedrawing aflords a fragmentary perspective and sectional view along a roadway being built in accordance with my invention, illustrating various stages of its construction. For clearness, portions of the pavement correspondin to these stages are arbitrarily divided 0 from one another by dot and dash lines.

In constructing a bituminous-topped pavement according to my invention, the first operation (after preparation of the sub- Igrade) is the laying of the foundation or ase 5, which is preferabl wet-cemented or concreted. On this is laid the bituminous upper portion or top 6 of, the pavement, bonded to the base 5 with bituminous emulsionsuch as that known in the road building art as cold repair cement. Owing to the presence-of the water in the emuls on, wetness -of the material forming the base 5 does no harm; on-the contrary, indeed, it rather tends to facilitate and improve the adherence of the top 6 to the base. When hydraulic cement is used in the base 5, its

capacity for taking up water in hardening tends to assist in the drying out of the bituminous emulsion. s

Before layin of the base 5 is begun, the sub-grade 7 s ould be properly shaped, rolled, and compacted, so as to be parallel to the intended surface of the finished pavement" and at a proper depth below, it. In

general, the depth of the completed pave-.

ment should beabout 9.in.; but it may be considerably deeper where unusually heavy loads are anticipated. The variation in.

depth should be in the base or foundation 5,the thickness of the top 6 remaining sub ,stantially the same. A top 1 in. thick'represents good general practice.

In order to avoid the necessity for crushed stone, I prefer to build the base or foundation 5 after the old Telford mode of construction, laying suitable stones 8, 9 endwise or edgewise on the sub-grade, well compacted together, and grouting them with cement or mortar,rather than the mud employed by Telford. Thus I form a solid, non-yielding concrete base with a minimum of hydraulic cement. Starting with field or ledge stones, approximately 8 in. in their longest dimensionand not less than 2 in. in their shortest din ension, I lay them on their natural beds, by hand, in direct contact with stones 8, 9 are well bedded and the generalsurface is as nearly parallel to the intended final grade as is practicable and about 1 in. below it. Any projecting stones should be napped off to grade. Voids inthe surface less than 2 in. in depth or width should not be filled at this stage.

Having been thus rolled and trued up, the stone surface should be thoroughly wet (with a hose and all dirt or vegetable matter washed om the stones. The grouting may be done immediately after this wetting and washing, while the stones are still wet. I prefer to apply the grout in two pourings, ,one very thin and wet, so as to ,flow freely and fill all the lower interstices, and the other somewhat thicker, to fill in the cracks on top of the first. For the first pouring may be used a Portland cement mortar consisting of one part of cement and two parts of clean, sharp sand (by volume), and carrying an excess of water so that it will flow readily. When thismortar 10 has settled the same proportions as the first, but with only enough water to give it a creamy consistency. hen this is being applied, the surface voids may preferably be filled with small stones. 12 not exceeding 1% in. in-

inous" top 6 may be spread and compacted directly upon the green, wet concrete. This top may consist. of emulsified asphalt (such as cold repair cement) as a binder and a suitably fine aggregate, such as coarse sand with a finer filler. A suitable mixture is as follows Bituminous emulsion 10 to 3 Stone dust 15 to Coarse sand 70 to 80% This top mixture may be prepared on the job, by mixing the materials cold in the same manner as the hydraulic cement grout for the base; indeed, it may even be mixed in the. very same concrete mixer. It should be laid upon the green concrete base to such a de th that when compacted by a tandem ro ler, it will have the desired thickness, about 1 in., say. A very light coat of asphalt emulsion mixed with about 10% water may then be broomed over the surface and covered with sand, or stone chips, as at 14. The water from the bituminous top 6.will dry outby evaporation, etc., leaving the top as a compact, homogeneous coat firmly adherent-to the concrete base 5. As already stated, the whole operation is accomplished without-the use of heat, either in the preparation of the raw materials, or in spreading and compactiiig them.

Having thus described my invention, I claim 1. The method of constructing a pavement with cemented base and bituminous top which comprises laying a Telford stone base, wet-grouting and then brooming said base, so as to leave the tops of its stones projecting above the grout, and laying the top directly binder.

2.- The method of constructing a pavethereon with bituminous emulsion ment with cemented base and bituminous top which comprises laying a Telford stone base, grouting said base with thin, fine flowing hydraulic cement grout, to fill its lower interstices, cracks with thicker hydraulic cement grout,

and then substantially filling its and laying the top directly thereon with bituminous emulsion binder.

In testimony whereof, I have hereunto signed my name at Melrose, Mass, this 23rd day of January, 1925.

1 RALPH G. HEATH.

Images