Quality Control During Mixing/Placement
Drum Rotations of Transit Mixer/ Agitator Another test method is to count the actual rotation of the ready mix truck drum rotations. Once the mix and water are placed in the drum the load should be delivered and discharged before the drum has revolved 300 times. Over-mixing concrete damages the quality of the concrete. Over-mixing may: • Grind the aggregate into smaller pieces, • Increase the temperature of the mix, • Separate the aggregates from the cement paste • Lower the slump, • Decrease air entrainment, and • Decrease the strength of the concrete. Also, over-mixing puts needless wear on the drum and blades of the transit mixer Time An important quality control test for concrete is to identify the length of time from when water is added to the mixture until the mixture is poured. The batch ticket has the elapsed time recorded between the mixture and the placement. Concrete begins to stiffen as soon as the cement and water are mixed. However, the degree of stiffening th...