[Amended 2-28-1950 by G.O. No. 6-1950]
For pavement base, the following types are hereby prescribed,
approved and adopted, all to be in accordance with the requirements
set forth in this article:
A. Portland cement concrete.
C. Asphalt macadam (penetration method).
[Amended 2-28-1950 by G.O. No. 6-1950]
A. Asphalt-macadam base shall be not less than three inches thick after
compaction and shall be of greater thickness if called for on the
plans or in the job specifications. It shall consist of a mixture
of two parts of one-and-one-half-inch and one part of three-fourths-inch
trap rock uniformly spread to such a depth that, after the application
of the asphalt cement and the small-size stone hereafter specified,
the compacted base will be of the thickness called for in the job
specifications or directed by the Engineer. The stone thus spread
shall be thoroughly rolled with a ten-ton power roller to the satisfaction
of the Engineer. The surface shall be left smooth, clean and of firm
texture.
B. On this surface, when dry, the approved asphalt cement, heated to
a temperature of not less than 275° F. and not more than
350° F., shall be applied to the amount of 1 1/4 gallons
per square yard, unless this quantity is changed by the Engineer.
For this application of asphalt cement, an approved pressure distributor
shall be used, with a pressure of 50 pounds per square inch or more
as directed by the Engineer.
C. Immediately after the application of asphalt cement, three-eighths-inch
trap rock shall be spread over the surface in such quantity as to
completely fill the voids in the larger stone. This course shall then
be rolled, adding additional three-eighths-inch stone if necessary
until thorough compaction is secured and the surface is true to cross
section and in conformity with the established grade. Surplus three-eighths-inch
stone shall be broomed off before the wearing course is placed.
D. In the case of small jobs where it may be impractical to secure a
mixture of one-and-one-half-inch and three-fourths-inch sizes for
the large stone in the base, the use of one-and-one-half-inch stone
may be permitted at the discretion of the Engineer. Also on small
jobs where the use of hot asphalt cement is not practical, the Engineer
may, at his discretion, allow another type to be used.