Dear reader we are discussing here influence of concrete mixer on air entrainment; in our upcoming post we will discuss about influence of aggregate and cement on performance of air entraining admixtures. The mixture we use may be
The usual maintenance work of mixer is to clean it after mixing is completed so that no residue of hardened or semi-hardened concrete remains on surface of drum and also on the blades. If proper cleaning is not done the blade may be coated by hardened concrete, sometimes the blades may also be worn out.
Such worn out and or coated blades may reduce air entrainment in concrete for a given mixer.
Some factors that influence air content related to concrete mixer are:
a. Air content is increased when a mixer runs loaded with ingredient lesser than its capacity
b. Air content is decreased when a mixer is loaded exceeding its capacity.
c. It is very difficult to develop air entrainment in drum mixer of capacity of small loads
It is observed that air entrainment increases throughout first 70 revolutions of mixer after that they remain constant for short duration and after that a decreasing trend is observed.