3.5.5
Cold-Weather Curing and Protection
When the daily outdoor low temperature is less than 0 degrees C 32 degrees F,
the temperature of the concrete shall be maintained above 5 degrees C 40
degrees F for the first 7 days after placing. In addition, during the
period of protection removal, the air temperature adjacent to the concrete
surfaces shall be controlled so that concrete near the surface will not be
subjected to a temperature differential of more than 15 degrees C 25
degrees F as determined by observation of ambient and concrete temperatures
indicated by suitable temperatures measuring devices furnished by the
Government as required and installed adjacent to the concrete surface and
50 mm 2 inches inside the surface of the concrete. The installation of the
thermometers shall be made by the Contractor at such locations as may be
directed.
3.6
SETTING OF BASE PLATES AND BEARING PLATES
3.6.1
Setting of Plates
After being plumbed and properly positioned, column base plates, bearing
plates for beams and similar structural members, and machinery and
equipment base plates shall be provided with full bearing with nonshrink
grout. The space between the top of concrete or masonry-bearing surface
and the bottom of the plate shall be approximately 1/24 of the width of the
plate, but not less than 13 mm 1/2 inch for plates less than 300 mm 12
inches wide. Concrete surfaces shall be rough, clean, and free of oil,
grease, and laitance, and they shall be damp. Metal surfaces shall be
clean and free of oil, grease, and rust.
3.6.2
Nonshrink Grout Application
Nonshrink grout shall conform to the requirements of paragraph NONSHRINK
GROUT. Water content shall be the minimum that will provide a flowable
mixture and fill the space to be grouted without segregation, bleeding, or
reduction of strength.
3.6.2.1
Mixing and Placing of Nonshrink Grout
Mixing and placing shall be in conformance with the material manufacturer's
instructions and as specified. Ingredients shall be thoroughly dry-mixed
before adding water. After adding water, the batch shall be mixed for 3
minutes. Batches shall be of size to allow continuous placement of freshly
mixed grout. Grout not used within 30 minutes after mixing shall be
discarded. The space between the top of the concrete or masonry-bearing
surface and the plate shall be filled solid with the grout. Forms shall be
of wood or other equally suitable material for retaining the grout and
shall be removed after the grout has set. If grade "A" grout as specified
in ASTM C 1107 is used, all surfaces shall be formed to provide restraint.
The placed grout shall be worked to eliminate voids; however, overworking
and breakdown of the initial set shall be avoided. Grout shall not be
retempered or subjected to vibration from any source. Where clearances are
unusually small, placement shall be under pressure with a grout pump.
Temperature of the grout, and of surfaces receiving the grout, shall be
maintained at 20 to 30 degrees C 65 to 85 degrees F until after setting.
3.6.2.2
Treatment of Exposed Surfaces
After the grout has set, those types containing metallic aggregate shall
have the exposed surfaces cut back 25 mm 1 inch and immediately covered
SECTION 03301A
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