US1639276A - Roadway construction - Google Patents

Description

' a superficial surface of the pavement.

Patented Aug. 16, 1927.

PATENT OFFICE.

AUGUST E. SCHUTTE, OI NORTHBORO, MASSACHUSETTS.

noAnwAY CONSTRUCTION.

IojDrawing.

My invention relates to a method of securing and cementing thin roadway surfaces to their foundations such as Portland cement concrete, brick or other material, and is especially designed to re-surface concrete roadways. The invention resides primar ly in a method of rendering the concrete or other surface receptive and retentive of a bituminous coating upon which then can be placed, if desired, a bituminous wearing sufface, or the first and original bituminous layer can be used alone.

It is a well known fact that concrete road surfaces after having been in use for a while become scaly and uneven on account of p-ar ticles or small areas breaking off. Many attempts have been made to renovatesuch surfaces in various ways and especially by applying bituminous compounds such as tar,

asphalt and the like. All these attempts have beenunsuccessful. This is primarily due to two factors.one isthe moisture inherent in a porous concrete structure, and the other is dust which is always presentfon bituminous material is placed upon such con-' crete surface, the moisture absolutely revents adhesion and if the upper surface should be dry, it is always more or less covered with dust which it is impossible to remove, and which prevents the penetration of the bitumen sothat upon chilling it-scales off and is removed by traific. If the bituminous material placed upon such a surmitting the thin oils to penetrate to a short distance, leaving the'heavier oils, at the sur face. In such a case the bituminous layer is only held temporarily for the thin :oil penetrates deeper and deeper into the structure,

leaving the heavier medium resting on the A, I surface, so that after a short time it scales take place: First, the asphalt so heated be-v comes very. fluid and penetrating, easily and rapidl entering the pores of the structure.

Secon the execessive heat of the penetrata lication filed ma 29,

face is of a thin and oily-nature, the dust P and the structure itself acts as a filter, per- 7 1922. Serial No. 578,502.

ing asphalt evaporates the moisture at the immediate surface of the'roadway and-it escapes throu h the thin, limpid asphalt. Since the sur ace of the asphalt on the concrete structure is very thin, the bubbles formed by the vapor or steam easily burst and allow the steam to escape, while the heat still applied at the surface kee s the asphalt so liquid that it immediately fills the space left by the bursting bubble and forms a continuous thin asphalt surface which is thus keyed to the concrete structure itself and on hardening forms a non-scalable, bi-

' tum-inous surface.

The bituminous surface thus formed is naturally retentive of any bituminous struc Y ture subsequently placed upon its to' so that it can be thickened to any desired thickness by applying upon it by any suitable means more asphalt composition, or an asphalt composition containing a large percentage of asbestos fibre to toughen itsuch as is described in my U. S. Letters Patent No. 1,265,259, dated May 7, 1918, or any other suitable tough bituminous 1ayer..

It is a well known fact among engineers and road builders that the wear of a bituminous roadway depends to a great extent upon the bitumen content in the mixture, i. e.

the same grade of asphalt beingused, a

mixture containing a: greater amount of such asphalt will bea mixture which will wear longer and better than one .hav'ing less asphalt, provided the mixture can be kept in lace and prevented from shoving and rutting. It has been impossible heretofore to use such rich thin mixtures because no'me'ans were found to anchor them to the foundation so that they naturally were shoved and broken up by trafic i If again such rich mixtures were laid thick, while they would resist abrasion, they would not-resist the dead weight of traffic and soon formed ruts and channels and became useless.

With my method of anchoring such coatin s securely to a rigid concrete foundation, it is possible thereby to cement them to such foundations and'so to cover the foundation with a very tough, thin layer of bituminous compound, containing fibres like asbestos, with or without the'addition of mineral matter, and thereby produce an excellent roadway. Old'concrete roadways can thus be renewed andold bitumlnous surfaces canbe toughened, revived and leveled. Not only is crete by my method, but the concrete itself is toughened and strengthened at the point of contact bybeing cemented at the line of juncture by two cements, a: concrete and bituminous.

I To practice my invention I proceed as folows-:--

Assuming that an old concrete road is to,

, pores, crevices and voids on the side of the cracks. The Whole surface is then treated by spreading bitumen, either in a liquid form or in the form of powder or chunks, and applying intense heat,heat which will melt the bitumen and raise it to a tempera ture above its flash point, such that it may cause the surface being treated to burst into flame, liquefying the asphalt, evaporating the moisturein the concrete and penetrating into it. The distance of penetration depends upon the lengthof application of the heat, but for paving surfaces the light penetration of a sixteenth of 'an inch or. so is suflicient to secure adhesion, and this can be achieved in a few minutes. The means of heating can be-either direct flames, which is the simplest way, or can be superheated steam, superheated air, gas or any other suitable means for producing intense heat.

- After. the surface has thus been treated, it

is found that some of the asphalt has penetrated moreor less into the structure, leav-- ing the most of it on the surface as a con.- tinuous thin layer. Such treatment alone is sufficient for surfaces exposed to pedestrian traflic, such as sidewalks and especially fac tory floors. For street roadways, however, it is preferable to thicken this bituminous surface. A hot bitumen will stick, adhere to, become commingled with and be retained by a bituminous surface. Therefore to thicken the layer of bitumen on the treated concrete surface, it is only necessary to apply a secondary coating of a rich bituminous mixture at a temperature hot enough to melt or. soften the bitumen below, so that the two layers will coalesce. This secondary coat, if such is used, is preferably one composed of asphalt, having incorporated therewith short absestos fibre and, if desired, some sand, and applied at a heat of about 350 degreesFahrenheit; or a rich mixture of sand and bitumen can be applied or, in fact, any rich, tough, bituminous com osition. These can be troweled on or p aced there by any suitable machine and after being slightly chilled, are treated with a superficial scattering of clean sand, which will not penetrate the structure itself, but will lie on the top and be slowly impressed into the surface'by-trafiic, giving the structurea gritty, sand-paper-like surface.

While my invention relates especially to the repair of concrete surfaces, it may be used with such surfaces when freshly laid,

or in fact with any surfaces to which it is necessary to bind a bituminous layer. In using the term roadway I mean to include any wearing surface subject to travel of any kind such as highways, sidewalks, floorings, etc., and in using the term foundation I mean the surface which receives the bituminous coating and to which such coating is to be united, whether it be-made of concrete, bitumen or other material, for the essence of my invention relates to the maintaining of the coating ata temperature approximately or above its flash point, Whereby its temperature will effect a penetration of the foundation by the coating or the intermingling of the two so that they are tied together.

What I claim as my invention is 1. That method of uniting a bituminous coating to a concrete roadway surface which consists in applying said coating to said surface and raising it to a temperature. approximating its flash point and maintaining it at such temperature for a short period of time whereby a portion of it will penetrate said surface and the remainder will form a protective coating therefor. 1

2. A method of adding a. bituminous layer to a concrete surface which consists in heating the concrete, applying a bituminous compound such as asphalt, heating said asphalt to its flash point whereby it will enter the poresand evaporate the moisture, and then applying a secondary wearing surface thereto.

AUGUST E. SCHUTTE.