Specifications

07/22/10 03001-4
more than one in six, and in the case of tied columns, space the ties not more than 3 inches on
center for a distance of one foot below the actual point of offset.
G. Protection of Reinforcement: Protect the metal reinforcement by the thickness of concrete
indicated on the Drawings. Where not otherwise shown, the thickness of concrete over the
reinforcement should be as follows:
Where concrete is deposited against ground without the use of forms, not less than 3 inches for
beams and slabs.
Where concrete is exposed to the weather or exposed to the ground but placed in forms, not less
than 2 inches for bars more than 5/8 inch in diameter and 1-1/2 inches for bars 5/8 inch or less in
diameter.
In slabs and walls not exposed to the ground or to the weather, not less than 1-1/2 inches.
In beams, girders and columns not exposed to the ground or to the weather, not less than 1-1/2
inches.
In all cases, the thickness of concrete over the reinforcement must be at least 1-1/2 inches.
H. Protect reinforcement bars, intended for bonding with future extensions, with approved adequate
covering.
3.03 JOINTS
A. Expansion and Contraction Joints: Provide expansion joints when slabs on grade join other
construction and elsewhere as indicated. Expansion joints are to be one-half (1/2) inch thick
when not otherwise noted. Tool edges of slabs at expansion and contraction joints to a one-fourth
(1/4) inch radius.
B. Construction Joints: In jointing fresh concrete to that which has already set, the surface of the
concrete in place must be thoroughly cleaned and have all laitance removed by cutting with a
suitable tool. In addition, wet and slush with a coat of grout, no leaner than one (1) part cement
to two (2) parts sand.
3.04 CONCRETE MIXING
A. Mix until there is a uniform distribution of the materials and discharge completely before the
mixer is recharged.
B. For job-mixed concrete, rotate the mixer at a speed recommended by the manufacturer and mix
continuously for at least one minute after all materials are in the mixer.
C. Mix and deliver ready-mixed concrete in accordance with ASTM C-94.
D. Wet batches of concrete may be transported in either agitating or nonagitating trucks. When non-
agitator trucks are used, the elapsed time between the addition of water to the mix and depositing
the concrete in place must not exceed 45 minutes except that when a retardant admixture is used
such elapsed time must not exceed 75 minutes. When the handling is done in truck agitators,
such elapsed time must not exceed 60 minutes, except that when a retardant admixture is used a
maximum elapsed time of 90 minutes will be permitted.
E. When concrete arrives on site with slump below that suitable for placing, as indicated by the
Specifications, water may be added only if neither the maximum permissible water-cement ratio
nor the maximum slump is exceeded.
3.05 PLACING CONCRETE