Proper mixing coats every particle of aggregate and fills all the spaces between them with cement paste. For most home repairs, concrete can be hand mixed. The methods for mixing concrete by machines vary. The concrete may be mixed by machines at the place where the concrete will be used. Ready-mix companies make huge batches of concrete at mixing plants, and haul it to the work site in trucks.
Some firms use mixing machines mounted on trucks.
These machines mix the concrete as the truck carries it to the building site. Homeowners can buy prepared mixtures of cement and aggregates for small repair jobs. Only water has to be added to such mixtures. Workers place the freshly mixed, wet concrete into forms made of wood, plywood, or steel. The forms hold the concrete in shape until it hardens.