the pipe shall be at least three times the nominal maximum-size coarse
aggregate in the concrete mixture to be pumped but not less than 100 mm 4
inches. Aluminum pipe shall not be used.
3.1.5
Vibrators
Vibrators of the proper size, frequency, and amplitude shall be used for
the type of work being performed in conformance with the following
requirements:
HEAD DIAMETER
FREQUENCY
AMPLITUDE
APPLICATION
mm
VPM
mm
Thin walls, beams, etc.
32 to 64
9,000 to 13,500
0.5 to 1.0
General construction
50 to 88
8,000 to 12,000
0.6 to 1.2
HEAD DIAMETER
FREQUENCY
AMPLITUDE
APPLICATION
INCHES
VPM
INCHES
Thin walls, beams, etc.
1-1/4 to 2-1/2
9,000 to 13,500
0.02 to 0.04
General construction
2 to 3-1/2
8,000 to 12,000
0.025 to 0.05
The frequency and amplitude shall be determined in accordance with COE
CRD-C 521.
3.2
PREPARATION FOR PLACING
3.2.1
Embedded Items
Before placement of concrete, care shall be taken to determine that all
embedded items are firmly and securely fastened in place as indicated on
the drawings, or required. Embedded items shall be free of oil and other
foreign matter such as loose coatings or rust, paint, and scale. The
embedding of wood in concrete will be permitted only when specifically
authorized or directed. Voids in sleeves, inserts, and anchor slots shall
be filled temporarily with readily removable materials to prevent the entry
of concrete into voids. Welding, including tack welding, will not be
permitted on embedded metals within 600 mm 2 feet of the surface of the
concrete.
3.2.2
Concrete on Earth Foundations
Earth surfaces upon which concrete is to be placed shall be clean, damp,
and free from debris, frost, ice, and standing or running water. Prior to
placement of concrete, the earth foundation shall have been satisfactorily
compacted in accordance with Section [_____].
3.2.3
Concrete on Rock Foundations
Rock surfaces upon which concrete is to be placed shall be clean, free from
oil, standing or running water, ice, mud, drummy rock, coating, debris, and
loose, semidetached, or unsound fragments. Joints in rock shall be cleaned
to a satisfactory depth, as determined by the Contracting Officer, and to
firm rock on the sides. Immediately before the concrete is placed, all
rock surfaces shall be cleaned thoroughly by the use of air-water jets or
sandblasting as described in paragraph CONSTRUCTION JOINT TREATMENT. All
rock surfaces shall be kept continuously wet for at least 24 hours
immediately prior to placing concrete thereon. All approximately
SECTION 03301A
Page 32
Previous Page
