READY MIX CONCRETE

•Ready mix concrete is concrete that is made at ready-mixed plant and then transported to the site in rotating-drum trucks or transit mixers.
•Proportioning, batching, mixing and delivery are all done by the concrete supplier.
•High quality control
•Advantages of using ready mix concrete:

a) better quality concrete due to usage of trained personnel and automated equipment.
b) elimination of material storage on congested building sites- no need to allocate place at site for storage of cement, aggregate, sand
c) save the contractor’s time and usage of labour’s energy to mix the concrete 

•For ready mix concrete supply, the purchaser should specify the following: 
a) Designated max. size of coarse aggregate
b) Desired / max. slump at the point of delivery
c) Air content (for air entrained concrete)
d) Mix design requirement – such as cement content, max. water content & admixtures or minimum compressive strength at 28 days
e) Unit weight required (for structural lightweight concrete).

Imp points abt mixing of concrete

MIXING

•Done in order to ensure each particle of aggregate in fresh concrete will be coated with the cement paste

•Also to give a homogenous even coloured product.

•First stage of mixing is called “BATCHING”.

•Batching is process where it involves weighing out or measuring out all of the ingredients for a batch of concrete.

•The materials that are mixed at any one time constitute a batch.

•Quality of concrete depends on the accuracy of the batching operation.

•However, thorough mixing is essential for complete blending of the materials that are required for the production of homogeneous, uniform concrete.

•Inadequate mixing result in lower strength.

•There are 2 method for concrete mixing that is:  

    a) hand mixing

    b) machine mixing

•The biggest problem with concrete produced with construction mixers on site is quality control.