US2220149A - Method of constructing bituminousbound wearing surfaces for roadways and streets - Google Patents

Description

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ENQQQQ QQQQW RS S@ SURFACES FOR ROADWAYS ND STREETS Nov. 5, 1940;

METHOD CF CONSTRUCTING BITUMINOUS-BOUND WEARING Everett Finley BY y ATTORNEY.

Patented Nov.;u, 1940 BOUND WEABlNG S WAYS AND srEErs samEvei-ett Filey, Atlanta, Ga.

Application October 14,

Plx'rENT oFFlcE 2,226349 METHOD oF coNsTBUcTlNG BIT [JWN OUS- URFACES nFOR ROAD- 1931, serial no. 168,852

4 claims. (C1. en -z3) This invention relates toa, method for constructing bituminous-bound Wearing surfaces for roadways and streets. lMore particularly it relates to the use of liquid bitumensas a prime coat in building thin bituminous-bound roadway surfaces of the-type generally called "surface treatmentsf? double surface treatments, inverted penetration and the like. According to this invention liquid 'priming bitumen is for the first time poured, or applied by pressure, over uncoated aggregates previously spread on the foundation,A whereby the priming bitumen serves simultaneously to prime both the said uncoated aggregates and the foundation under` the aggreto the primed aggregates, Ais conveyedl entirely` around each particle of such aggregates and over and into the surface under the aggregates.`

It is old to the art to prime foundations upon which thinor relatively thin bituminous surfaces are constructed, and the value lof such priming of road or street foundations has throughout the World proved its value. It is new to apply a primingbitumen in such a manner that it will con.

layer of uncoated aggregates spread, on that foundation, and to later use such priming coat as a means or agent to facilitate the subsequent coating of such mineral aggregates with a heavy bitumen by conveying `said heavy bitumen around said aggregates, to the end that said aggregates w111 be rmiy bonded together. This lnovel use of the priming -bitumen constitutes the present invention, 4and roadways and streets so con- 35 structed have proven thatit is not only equally'.

important, if not much more so, /to prime the aggregates as it is to prime the foundation, and

` roads and streets so constructed have in like manner proven that the heavier or subsequent,

40 application of bituminous cement over the precoated aggregates, not only uniformly coats such aggregates themselves, but the heavier bituminous cement .is drawn down and into the foundation y itself. In accordance with the prior art, there 4g was no thorough coating of the uncoated mineral aggregates, and the subsequent layers .of bituminous cement applied, laid overfthe immediate surface and did not coat, even in double surface ltreatment,l more than thesurface of said ag- 50 gregates'. j In the preferred manner of carrying out my .invention,Iproceed as followszf On any suitable foundation that is inpropershape, orthat has been properly shaped and 55 bonded, I spread a layer of uncoated aggregates,

gates, and whereby heavy bitumen, later applied s currently prime both the foundation and the f constituting the major part of the wearing surface that'is tobe built, whichL Wearing surface may be of any desired thickness. Over this layer of uncoated particles I apply sufficient'. priming bitumen to" not only coat the surface of all aggregate particles, but toflow between such particles to the foundation below, where the bitumen spreads out to cover and to prime the foundation. I thus simultaneously prime both the aggregate particles and the foundation upon which the layer of aggregate has been spread. I thereafter comvplete the construction of the surface in any standard manner, that is, I may apply alternate layers of bituminous cement and aggregate until the desired thickness is constructed, or I may apply a. single layer of the bituminous cement,

using `a. pre-mix with a stable bituminous binder and a volatile*solvent,'as dis osed in my United VStates Letters Patent No. 1,7 0,096, or suflicient plant mix, either hot k6r crc-ls type, using the primed base and aggregates a binder course', to bring the total thickness to the required amount.

Priming bitumens as used in road building have similar functions `to priming paints used in covering wood, that is, the priming bitumen is suiiiciently fiuid `to penetrate andA flow', into all sur- `face openings in the material primed, so that waterfcannot later penetrate that surface; Also, the priming bitumen spreads out over the surface primed and forms a very thin adhesive layer to which the heavy bitumen will cohereperfectly and with maximum strength not developed when theheavy binding bitumen is applied directly to an unprimed surface. The knowledge of what constitutes asuitable'priming bitumen is common to the art, and maybe found in current specifications and texts.y

` According to prior practice,y the thin bitumif nous-bound surfaces herein mentione'd are ordinarily constructed in stages 'or layers of alternate applications ofbitumenand aggregate. 'I'he lowi est orrst layer isusually a. prime coatof bitu# men appliedto the -lfoundation and given time to. cure. Over this curedl prime there is next aplied a layer of bituminous cement, followed with ternate layers of mineral aggregate and bituminous cement to make up the total required thickness of thenished surface. The lowest /layer of the mineral aggregate is'the largest in amount and in Vsize of particles. In fact, this first layer of aggregate generally constitutes more than half the total thickness of the entire bituminousbound surface and much more than half of its structural strength. 1f this ayer fails, the entire u :itsA

structure immediately fails. The prior practice is to place this layer of aggregate in an uncoated condition on the layer of heavy bituminous cement, and to apply over it another layer of bitu-l minous cement. The bituminous cement is ex pected to adhere to the uncoated stone without benefit of a prime coat, much as heavy paint might be expected to adherev to rough porous wood without benefit of a priming paint. A heavy paint so applied .would of course soon peel off because it is not sufficiently fluid and penetrating to serve as a rrimecoat. If it were made thus fluid and pene rating it would lack the required.

stability to serve as a binding cement. As aresult of this application of heavy bituminous cement direct to the major part of the structural.

Prior practice in building the type of thin bituminous surfaces herein considered requires that the initial layer, that is, the prime coat, be' dried out or cured before spreading another layer upon it. This process generally requires from lten days to three weeks and the roadway is generally closed to traffic and the public denied the use thereof, because during this curing process the surface of thev roadway may be sticky and slippery, and therefore very difficult for traic, which would pick up areas of the prime coat, leaving bare uncoated areas that must be repaireg before construction is continued.` In instances where thewet prime is covered with a blotting coat of fine .or dusty material to help ameliorate the stickiness, this dust is a nuisance to trailic and must be swept off before another layer of the surface is added, again adding to the cost, both in labor and lcost of covering with blotting material. Furthermore, most prime coats, afterdrying out, become brittle and are easily cracked by the pressure from the sharp corners and edges of the coarse aggregate spread upon it and pressed into it by rollers and by traffic. These cracks permit the passage of water and are largely responsible for the many pot-holes and-disintegrated areas appearing so frequently in thin bituminous-bound surfaces, and causing endless repair and maintenance. With the use of my invention, all of these defects .are removed. There is no pick-up of the prime from the foundation because the foundation is protected from contact with tramc by the coarse aggregate. There is no long wait for the dryingout`\process because I prime the materials and within twenty-four hours add the required top,

' thus saving a great part of the cost of construction. This`permits me to lay the prime coat one day and to complete the entire surface, ready for traffic, the next day. I thus reduce the cost and save immensely on. traffic-use.

- Under my invention, on types of highways and streets-that are bonded with water, such as water-bound macadam, clay gravel, sand clay and the like, the coarse aggregates are rolled before the wet prime cures, and therefore the particles are seated before any brittleness can occur and there is no further driving of the particles of the coarse aggregate into the primed surface to crackl it. I thus prevent the type of failure known as pot-holes anld the following disintegration. Water, the worst enemy of pavements, cannot, with my invention, pass through any of my primed foundation, or between that primed foundation and the primed aggregate of the lower aggregate layer, or between the prime coat on that aggregate and the surface of the particle, whereas under-the prior art water could `and did do all of these things detrimental to the pavement. A further important time saving factor is that my vinvention may be practised and roadways surfaced under this method at any season 'of the year where the road foundation is dry, or relatively dry, and the temperature not below v42 F.,' whereas even in the Southern States, such as North Carolina. South Carolina and Georgia, no priming material is permitted to .be applied," under the old art, after October 15 or'November 1.

On other than the ater-boundtype, such as concrete, the resurfac rfsofsheet asphalt or as- -phaltic concrete, the primed bitumen acts as a tack or adhesive coat for the bottom of the coating of mineral aggregates spread over such a foundation, and with the same resultant surface oatlng of heavy bitumen, as above described.

l As a definite example of the method of carry-- ing out my invention, suppose it is desired to `build va bituminous-bound surface one and onehalf inches in thickness on any well-shaped and compacted base or foundation of the type that unusually requires about 0.3 of a gallon of cutback asphalt prime per square yard, I would proceed as follows:

Over the foundation I first spread a layer of stone passing a one and one-quarter inch mesh, and retained'on a one-half inch mesh, placing the particles in the desired relation to each other,

making'a uniform layer of the desired thickness. Over this layer of aggregate I then apply between 0.35 and 0.45 of a gallon of cut-back asphalt of the type specified below. Within twenty-four hours I roll this primed material and the water-bound types of foundations to seat the aggregate before the prime has set. I then complete the surface treatment either by adding sufficient plant-mixed material to bring the thickness up to the required one and one-half inches, or I complete the surface in any other standard) method, such as by successive layers of bituminous cement and aggregate.

The cut-back asphalt used in the above example shall substantially meet the following requirements when tested in accordance with standard practice:

Flash point; 150 to 250 F. Distillate to 600 F i 25 plus Viscosity, Saybolt 180 F ...150 to 250 F.

Solubility residue of distillation .99% in CS2.

It will be understood that the above specified priming material is one of the several types that may be used. I could, of course, use cut-back tar. In fact, anyl standard priming bitumen may be used. Also, in the above example, I have named a thickness of 1.5 inches. Any thickness of such surface now being constructed may be constructed under my invention, and any type of foundation now being used may also be used under my method. Modifications in procedure, relative to thickness, bitumen, quality and quantity of materials, amount of compression, etc., will be apparent, in the light of this disclosure, to those skilled in the art. a

If a coal tar priming product is used, one substantially meeting the following requirements when tested in accordance with standard practice would serve:

Specific viscosity, Engler 1049 F.- 18 to 25 Dstillate to 455 F., not over 40% Soft point residue R 8: B., not over 140 F. Bitumen soluble in CS2, at least- 90% Specific gravity (@T* F 1.1 to 1.22

Or, if the Wearing surface is to be completed by successive layers of bituminous cement, one substantially conforming to the following requirements, when tested in accordance withstandard lpractice:

Specific gravity 60 F., at least -.-1;02

Penetration at 77 F., 100 gr., 5 sec-.. 90 to 120 Open flash point, not less than,.... 390 F. Loss, 5 hrs. 325 F., not over 1% Ductility at 77 F., at least 100 cms. Bitumen soluble in CS2, at least.. 99%

The novelty ofy this invention lies in the novel l employment of priming bitumens to simultaneously serve several stages of construction, instead of the one stage formerly served, and wherein the structural and water-proofing features are vastly improvedwith a marked saving in timey and cost. l

Inv the accompanying drawing I have diagrammaticallyshown different ways ofpractising the present invention, but the showing therein made is to be understood as illustrative, only, and not as dening the limits of the invention.

In said drawing:

Figure 1. diagrammatically shows consecutive steps in producing a chipped stone wearing surface.

Figure 2 diagrammatically shows consecutive` steps cin l producing a pre-mixed top wearing surface. l

In themethod of Figure 1, step I consists in the preparation of the suitable base or foundation which may be of any appropriate kind and may be an old pavement which it is desired to r surface. This is followed by step II which co sists in spreading upon said base a layer of unpimed aggregate. Step III consists in applying the primer to the aggregate in such .quantity that it will thoroughly wet such aggregate, flow downwardly therethrough, and spread over, wetand soakl into the underlying base, after which the' aggregate is compacted. Step IV consists in applyingthe heavy bituminous binder to. envelop and bond the aggregates to one another through-` out the mass. And step V consists in the addition of stone chips to thel bituminous-bound surface of step IV to'complete the job.

According to the procedureof Figure 2, steps I to,IV, inclusive, are the same as in Figure 1, but step V of Figure 2 consists in theaddition to step IV cfa pre-mixed top layer iniieu of the 'stone chips of Figure 1.

wearing surfaces for method which comprises preparing a suitable foundation, thereafter spreading upon said foundation, prior to priming the latter, ya layer of unprim'ed coarse aggregates, thereafter applying tg the resulting assembly a uid outback bitumi- 80 nous primer in suilcient quantity to flow downwardly over and between the aggregates and to spread over the foundation to 'simultaneously prime both of the theretofore unprimed aggregates and foundation, and thereafter applying a $5 bituminous binder to the thus primed aggregates and foundation; t

The foregoing detailed description sets forth the invention in its preferred practical forms of making or resurfacing pavements, as the case may be, but the invention is to be understood as fully commensurate with the appended claims. 5

In the appended claims I have referred to a outback bituminous primer as including both asphalt and tar.

Having thus fully described the invention,

what I claim'as new and desire to secure by Let- 10 ters Patent is:

1. In the art of constructing bituminous-bound l wearing surfaces for roadways and streets, the method which comprises preparing a suitable foundation, thereafter spreading upon said foun- 15 dation, prior to priming the latter, a layer of unprimed coarse aggregates, and thereafter applying to the resulting assembly a fluid outback bituminous primer in sucient quantity to iiow downwardly over and between the aggregates and 20 to spread over the foundation to simultaneously prime both-of the theretofore unprimed aggregates and foundation.

2. In the art of conscting bituminous-bound @lays and streets, the 25 3. In .tnart of constructing bituminous-bound wearing surfaces for roadways and streets, the method which comprises preparing a suitable 0 foundation, thereafter spreading upon said foundation, prior to priming the latter, a layer of unprimed 4coarse aggregates, thereafterapplying to the resulting assembly a uid outback asphalt primer in sufficient quantity to flow downwardly 4,5 over and between the ,aggregates and to spread` over the foundation to simultaneously prime both of the theretofore .-unprimed aggregates and e foundation, and thereafter applying a bituminous binderto the thus primed aggregates and foun- 50 dation before said bituminous primer has cured.

4. In the art of constructing bituminous-bound inous primer has cured. o5 SAM EVEREI'I FINLEY.

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