A Study of Mixing Performance of Large Central Plant Concrete Mixers

摘要

Extensive field tests were conducted on four central plant concrete mixers of 8 cubic yard capacity, used on concrete pavement construction projects in four States. Multiple samples obtained at both the plant and roadway from nearly 400 test batches were tested for slump, air content, unit weight of fresh concrete, weight of aggregate retained on the No. 4 sieve (after washing one-half cubic foot of concrete), AND 28-DAY COMPRESSIVE STRENGTH OF TWO CYLINDERS FROM EACH SAMPLE. Uniformly good quality concrete was produced in some instances in 30 seconds mixing time. Specified minimum mixing time should be determined by plant-mixer performance tests based on three samples taken from the front, middle, and rear portions of each test batch discharge.