Sidewalks, curbs and combined curbs and gutters shall be constructed
in two courses.
A. The base course shall consist of a 1:2:4 mix by volume
of air-entraining portland cement, sand and gravel, mixed with water.
B. The top course shall consist of a 1:3 mix by volume of
air-entraining portland cement and sand, mixed with water, and shall be applied
within 25 minutes after placing the base course. The top course shall be one
inch thick and cover all exposed surfaces, including the face of curbs.
Sand and gravel shall be screened, graded and washed free of injurious
amounts of clay, loam and dirt. Sand shall be sharp, coarse, natural sand.
Gravel shall be No. 1 size, crushed gravel or broken stone. Mixing water shall
be suitable to drink. All materials shall be kept separated to prevent intermixing
and the intrusion of foreign matter. Cement shall be protected from damage
by the elements.
All materials shall be accurately measured by volume. Batch boxes must
be used for measuring the correct amount of sand and gravel when charging
the mixer. Only full sacks of cement shall be used. No fractional bag mixes
will be allowed. All concrete shall be mixed for at least 1 1/2 minutes in
a clean, approved mechanical mixer until the color is uniform and there is
a uniform distribution of materials.