US2183253A - Road construction - Google Patents

Description

` Dec, 12, 1939. A. R. CHAMBERS .2,183,253

' ROAD CONSTRUCTIN Filed June 21, 1937 Fig. l

/1/ M6717' 0R: CHAMBRS v gym. M

A T7'OR/VE V ALL/50N ROBRT Patented Dec. 12, 1939 UNITE TES man

TENT I;

ROAD CONSTRUCTION Application June 21, 1937, Serial No. 149,434

In Canada September 12, 1936 Claims.

This invention relates to an improved base construction for roads or highways, culverts, foundations, telegraph poles, posts and the like.

The object of the invention is to overcome the 5f damaging effect of frost caused by heaving.

hasbeen observed that ice-lenses form and grow in the sub-base of roads at depths of one, two or more feet below the surface and these give rise to frost heaves and the so-called boils `in 101 theY road when climatic temperatures rise suf- 'ciently. Sub-soii temperatures at these depths are rarely lower than -20 F. The invention contemplates lowering the freezing point of water in the sub-base to or below these temperatures 15'- to prevent the formation of ice-lenses. In placing foundations for buildings, machinery, telegraph poles, fence posts, bridges and culverts,

somewhat similar conditions prevail. Although culverts are normally a substantial distance below the road surface, the open end of the culvert .permits the frost lto enter the ground beneath itandv the road surface is frequently pushed up by the freezing of sub-surface water.

Theaccompanying drawing illustrates the invention; Figures l and 2 as indicated illustrating road construction.

In accordance with the invention the sub-base of the construction to be stabilized against frost is impregnated with a water soluble electrolyte, soluble to such an extent as to lower the freezing point of soil water therein to a point below the temperature lto which it is commonly reduced during the cold season. This sub-base is rendered impervious to water by treatment with a waterproofing binder so as to retain therein the electrolyte. On this waterproof sub-base is preferably laid a base course, composed of a soil mixture stabilized with water soluble electrolyte, to the desired depth. In the case of a base for poles.

40 posts or the like the walls and bottom of the hole is coated with a tar or asphalt emulsion, bitumen or the like.v

The invention will now be described in detail with particular reference to road construction.

In carrying out the invention in practice, when grade and line of the road have been established and thesurface brought to a pre-determined subbase level, this surface is scariiied to a depth of, for example, 6 to 8 inches and a water soluble` electrolyte, preferably common salt, is thoroughly mixed, as by repeated blading, with the sub-base material, in proportions determined from an analysis of the sub-base material and the temperature against which frost protection is desired. As a guide to the determination of the amount of electrolyte to be used, the following formula, which is applicable to the use of sodium chloride, may be employed. It will be apparent that for other electrolytes the quantity m will krequire revision. B=165afcyem in which 5 Percent salt in soi; nes Freezing point 20 To illustrate, if a sub-base course 20 feet wide and 6 inches deep is to be protected against a temperature down to 13 F. and analysis shows the sub-base to contain 20% of nes of the character 30 described and to have a specific gravity of 1.3, the salt requirements would be tons per The mixture is then placed in position, moistened and compacted by rollers, trucks or any other convenient means.

The above formula and figures are for llus trative purposes and it will be understood that the amount of salt to be use-d under a given set of conditions may be determined by trial or otherwise as desired. The salt may be applied in solution where penetration to the required depth permits and conditions are such as to make this more economical.

As a means of further increasing the strength of the sub-base, the moist salt treated sub-base may be allowed to dry for a time to permit the formation of an interlocking network of crystalline particles throughout the structure. The increase in strength thus afforded appears to be due to the reduction of voids and to the intrinsic nature of the rock structure of the crystals themselves.

The sub-base thus prepared is rendered impervious to water by application of standard tar or asphaltio primer at the rate of say 0.5 gallon per square yard. If desired a thin layer of fine gravel may be rolled in and recoated as above to more effectively conne the electrolyte in the subbase material. This seal coat should protect the salt in the sub-base material from being leached out and thus retain the salt in the region of the origin of the frost trouble.

In cases where Water may enter the sub-base from below or the sides thereof it is preferable to coat with waterproong the bottom and sides of the sub-base excavation before replacing the backflll with the electrolyte therein in order to further insure the retention of the electrolyte.

The base course is then laid and consists of gravel, sand and clay of such size, gradation and proportions as to give a stabilized aggregate according to well known practice. Salt is preferably uniformly mixed with this material in proportions of about tons per mile of roadway 20 feet wide for a base course 3 inches thick. This course is preferably placed in layers each of which is dampened and compacted in place before the next is laid. This gives a dense and strong base which is preferably allowed a period of seasoning in actual use before the Wearing surface is applied.

In many cases this may be used as the Wearing surface but if a more permanent surface is desired cement, concrete or other bonded aggregate may be applied as in standard practice.

In preparing the base for culverts, piers, and other foundations the base soil is excavated and after the electrolyte is mixed therewith the mixture is returned into place with the Waterproofing to retain the electrolyte in the base soil.

In the case of pole or post holes after the base and wall of the hole are coated with waterproofing composition, the back-ll in which the electrolyte has been mixed is tamped into place about the pole, a thin layer of waterproof-lng composition is preferably placed thereover and the same is covered with earth to protect it from surface trailic around the pole. T'he salt electrolyte protects the pole from fungus growth and this substantially prolongs the life of the pole.

In constructing runways for ying elds or earth dams and reservoirs it is advantageous to place a thin layer of the waterproofing material at intervals as the electrolyte-stabilized soil mixture is laid to improve retention of the electrolyte in the soil concrete.

I claim:

1. In road construction, a sub-base comprising the subsoil and a water soluble electrolyte incorporated therewith, a waterproof coating to retain the eletrolyte in said sub-base and a Wearing course above said waterproofed sub-base.

2. A road construction comprising a sub-base composed of subsoil and a Water soluble electrolyte, a waterproof coating to retain the electrolyte in the sub-base, a graded aggregate base course and a Wearing surface on said base course.

3. Road construction as defined in claim 2 wherein the graded aggregate of said base course contains sodium chloride to stabilize the course and provide the wearing surface.

4. In road construction, the method I which comprises establishing the grade and line of the road in the normal manner, incorporating a water soluble electrolyte in the soil below said grade level to constitute a sub-base, sealing the subbase with a waterproof material to prevent escape of the electrolyte therefrom and laying a Wearing course above said sub-base.

5. In road construction, the method which comprises establishing the grade and line of the road in the normal manner, excavating the subsoil, incorporating therein a water soluble electrolyte, waterproofing the Walls of the excavation, placing the subsoil-electrolyte mixture in the excavation to constitute the sub-base of the road, Waterproong the surface of the sub-base, laying a base course thereon and applying a Wearing surface thereto,

ALLISON ROBERT CHAMBERS.

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