Question

The optimum number of revolutions over which concrete is required to be mixed in a mixer machine is

• A. 10
• B. 20
• C. 50
• D. 100

Answer 1

The correct option is B 20

One complete cycle of material is discharged after about 20 revolutions and it takes $2\frac{1}{2}$ to 3 minutes.

If the concrete is mixed for a comparatively longer time, it is uneconomical from the point of view of rate of production of concrete and fuel consumption.While if the speed of mixer is increased to reduce mixing time,the quality of concrete will be poor.