Developing Non-skid Road Surfaces

In the second direction, accompanying this outdoor ex­ posure, will be the standard laboratory tests on these same materials after they have been subjected to freezing and thaw­ ing, wetting and drying. Such laboratory work will, when compared to the outdoor experiment, tell us whether or not it is necessary to go through the actual construction of a test road in order to find out what may otherwise be predicted by the more simple and better controlled laboratory tests. One attempt is to find stabilization with Portland cement and also waterproofing with an additional admixture of bitu­ men, such as emulsified asphalt. One outcome of this experiment might well be the choice of material for shoulders, or for bicycle paths. There has been some insistence on the part of planners that the highway is a transportation path for general traffic as well as for autos on the pavement. It is true, as Upham said, that the early engineers who located and designed highways carried over principles from the railroad field, and the foot passenger was left out of the design. It is also expected that our laboratory research will investi­ gate the effects of exposure on bitumens. Thin films of these bitumens will be exposed, for example, to ultra-violet light, which now seems to be the criterion of resistance of these bitumens. Another useful field of investigation is a study of the testing process itself. At the present time, we have a number of tests for so-called stability, each one directed to find out the same property, as, for instance, the Hubbard-Field sta­ bility test, the ball test, the compression test, the Mini-track test, and the resistance of the materials to the forces which are generated either by the expansion of water into ice in freezing and thawing tests or the action of crystallization of materials like sodium sulphate. If it can be determined that one of these, the more simple test, will tell us what we want to know, there will be a great economy in laboratory opera­ tions. In conclusion, I wish to express my appreciation of the helpful relations with, and cordial co-operation of, the High­ way Commission and the Advisory Board. I desire to men­ tion also the chairman of the former Highway Commission, Mr. James D. Adams, under whose responsibility this project was initiated.