Materials that go into Highways

JULY, 1933 ARIZONA HIGHWAYS 11 Materials That Go Into Highways

EACH cog in any gear serves its purpose in turning the wheels which produce the finished product.

The Materials Division is one of these cogs in the huge enterprise of highway construction. For those who traverse our highways and appreciate the comfort they afford we give our best in service and up-to-date equipment.

The province of this department, as the name implies, is to determine what materials are satisfactory and, for those which prove unsatisfactory, what, if anything, may be done to remedy their unfitness. This necessitates a knowledge of tests and actual construction practice. Frequently materials will not conform to tests as they are found in the natural state, but by processing may be made satisfactory for use.

In building roads, or highways rather, for the latter term fits the low cost type now being built, it is absolutely necessary that all conditions be known. As in every vocation, either profession-

Laboratory Is Important Adjunct to Construction of Roads

al or scientific, the ability to serve is based upon the foundation principles. Every highway with inadequate foundation will eventually fail, or excessive The Bridge Division depends upon adequate foundations for its bridges; and so the highway depends upon the Materials Division for its foundation. Many inferior foundations could be used under the higher type pavement; but since, at the present time, our construction deals with the oiled gravel, it becomes necessary to use that type as a measure for the adequacy of base.

Testing base materials was given an added significance by the Bureau of Public Roads in 1931. Since that time we have followed their procedure and have benefited greatly therefrom. Suffice it to say that these tests place each soil in a certain classification and only certain classes have proved satisfactory for our purpose.

After the base has been taken care of from the knowledge gained by tests, it then becomes necessary to use the proper material for completing the surface.

Among the requirements of the De-partment of Agriculture, when setting up the machinery for carrying out the provisions of the Federal Aid Act through the Bureau of Public Roads, was that each state establish adequate facilities for testing and inspecting all materials used on federal aid work.

The Arizona highways department set up its laboratory in 1921. Since that time it has grown from a small room with practically no equipment, to a well equipped modern physical testing laboratory. It is needless to say that nearly any physical test can now be made here. The usual picture of a laboratory in the mind of the average person is a place filled with meaningless and peculiar apparatus. While it is true that the Materials Division has some such apparatus, a trip through the various rooms and a few explanations will lead to a better understanding.

Stepping out of the office into one of the workrooms, we encounter a man working on chemical analysis; at the (Continued on Page 26)