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 of cement concrete

• 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).