(b) When ambient temperatures drop progressively below 32F (0C) facilities will be needed to heat the
sand and stone stockpiles. Heating of the stockpiled sand and stone can be accomplished by
covering with a tarpaulin and blowing heated air under the tarpaulin with a construction type hot air
heater. Another means of heating the sand and stone can be accomplished by stockpiling the sand
and stone over a culvert pipe or similar type of pipe that may be fabricated from empty oil drums. A
fire can be maintained in the pipe or hot air blown in from a hot air heater. Covering the stockpile with
a tarpaulin will conserve heat to the greatest degree possible. If heating of the stockpiled sand and
stone is not possible, it will be necessary to have the sand and stone bin screens in place to remove
the frozen lumps and ensure that the aggregates have been dried or are frozen dry and free flowing.
(c) Spread and secure the tarpaulin over the sand and stone bins after the mixer is loaded (fig. 2-16).
The tarpaulin will retain heat to the greatest degree possible.
(4) Liquid Admix System.
The Liquid Admix System may be heated in the same manner as the water system. Check the mix design
for maximum temperature that the admix solution may be heated before loading on board the mixer
(5) Dry Admix System.
Production of concrete using the dry admix system shall proceed in the same manner as in normal weather.
b. See paragraph 3-11 for special instructions on cleanup in cold weather.
2-17. Operation in Hot Weather.
Follow these guidelines when operating the mixer in hot weather.
a. Keep the tarpaulin over sand and stone bins to keep aggregates from drying out.
b. Check with the mix designer to see if the water setting should be increased.
c. Clean up immediately when you stop operation. Concrete sets faster in warm weather and may harden on the
2-18. Operation in Humid Weather.
Follow these guidelines when operating the mixer in humid weather.
a. Be sure cement bin cover fits tightly.
b. Empty the cement bin at the end of the day.
c. Use fluffer valve to fluff cement frequently (fig. 2-37).