air-entraining agents can significantly improve the homogeneity and construction performance of fresh concrete mixtures. air-entraining agents also increase the durability of concrete structures, especially the frost resistance (i.e. freeze-thaw resistance) by multiples or even more than ten times, so they play an irreplaceable role in improving the comprehensive durability of concrete.
havinging an air-entraining agent, but no upper limit to the air content of concrete, should be no less than 3%.
air-entraining agents have certain water-reducing properties, and the water-reducing rate is required to be no less than 6%. mixing air-entraining agents into concrete will cause a reduction in strength, but the strength should still be maintained at 80%-90% or higher of the baseline concrete. this is why air-entraining agents and water-reducing agents are more often used in combination. .
the addition of air-entraining agents will significantly improve the frost resistance and durability of concrete. therefore, the retention value of the dynamic elastic modulus of a 28-d-old specimen after 200 freeze-thaw cycles should be ≥80 %. the bleeding rate of fresh concrete is less than 70%-80%, indicating its function of reducing bleeding.
in addition, the air-entraining agent has certain foaming properties and foam stability, but the bubbles should not be too many or too large, so it is required to be controlled within 5% of the error given by the manufacturer.
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