Machine mixing and slump of cement concrete

Machine mixing of cement concrete

Following points must be kept in mind for machine mixing of cement concrete.

Stone ballast, sand and cement to be pour into the cement concrete mixer.
For example, for concrete of ratio 1:2:4 first four boxes of stone ballast, then two boxes of sand and then one bag of cement should be put into the cement concrete mixer.
The machine then revolve to mix dry materials.
Then water should be added to the required quantity, 25 to 30 litres (5 to 6) gallons per bag of cement to have the required water cement ratio.
The mixing should be proper to have a plastic mix of uniform color.
It requires 1.5 to 2 minutes rotation for proper mixing.
Mixed concrete shall be unloaded on a masonry platform or on a iron sheet.
Output of concrete mixer is 15 to 20 mix per hour.

Slump test is carried out to control the addition of water into the cement concrete.
It is carried out to maintain the required consistency.
A slump of 7.5 cm to 10 cm (3 inch to 4 inch) is required for building work.
For road work it may be 3 to 4 cm (1.5 inch to 2 inch).