SURFACING OF ROADS

Evening Post, Volume CXVI, Issue 73, 23 September 1933, Page 13

SURFACING OF ROADS

THE USE OF CEMENT

RECENT MODIFICATIONS

One oi the most difficult problems iv building concrete roads is to secure a good foundation. A tub-base which will become moist thiough capillaiy attraction ia particularly objectionable. It lias been found that a layer of sand, gravel, or broken stone under the road surface will aid materially in prevent-, ing moisture from reaching tho con-, crete and causing it to deteriorate. The1 State of Louisiana, in America, has c\-1 perimented with cotton cloth j'or tho samo purpose. This was laid on a prepared sub-base and covered witli a heavy coating of asphalt. Under a gravel surface this method seems to have been satisfactory in waterproofing tho base. But in spite of all the experiments which have added to the knowledge of concrete, this material is far from being ideal for road surfaces. It is affected by changes in moisture content and in temperature. It cracks when contracting in cold weather; it heaves or is crushed when expanding in hot weather. It curves downward under tho rays of the sun; it curls upward during tho night. Highway engineers will continue to experiment in order to devise j methods which will overcome these faults in concrete. j Last year a good deal of. experiment

was undertaken in America with a road surfacing composed of broken stone cemented with cement grout. This surface is constructed 'just as a w&terlpound macadam road would bo built, except that instead of filling the spaces between the stones "■ with sciecnitfgs, they are filled with a. mixture '_,of cement,, sand, and water. Such a pa% ement has all the inherent good qujilifics of tit broken stone road, and, in .addition, its surface will not disintegjato under traffic. And, duo to tho fairly large stone used, this pavement is not subject,to those troublesome cratsks whicli require expensive maintenance. Best of all, it is loiv in first cost, having been constructed for about half ihe cost of & concrete road. From Kurope comes word tliat a cheap and durable high-type pavement has been constructed in Germany by surfacing ft broken-stono road With a bituminiscd cement. In this case either asphalt Or tar is mixed with cement, and the resultant material mixed with wtiter and sand, and 'spread over *he broken stone. A smooth, tough surface is produced after tho cement sets'Up which is especially resistant to temperature changes. It is repotted that the surface ,does not develop thoso cracks so objectionable in certain hightype pavements.