The factors affecting concrete intensity are shown as follows:
1. Rotation speed per minute
The rotation speed per minute is related to diameter of mixing drum. Generally speaking, it needs one to three minutes. One minute of mixing time is specific to with clean mixing drum and unworn mixing blades. If concrete is attached to mixing drum and mixing blades has been worn, the efficiency of machine will be reduced, which means that mixing time will be increased. Besides, rotation speed, which can also be shown as circular velocity, is connected with
size of concrete mixer.
2. Size of fine aggregate and coarse aggregate
With a particle size of 5 to 150 mm, cobble and broken stone belong to coarse aggregate. The maximum particle size cannot exceed a quarter of structural section’s minimum size as well as three quarters of rebate's minimum clear distance. As to with thickness equal to or less than 100 mm, maximum particle size up to one half of the plate of the aggregate can be used, but the quantity cannot exceed 25 percent. What should be noticed is that concrete cannot be used with slice that can be crushed easily and broken stone in a shape of strip or needle. Natural sand, such as sea sand and river sand, is usually used as fine aggregate.
