Analysis of compressive strength of concrete prepared by triplemixing technology depending on both the discharge and curing time

Compressive strength of concrete having recycled concrete aggregate is influenced by the properties and amount of those aggregate. The worse quality of RCA can be eliminated by specific mixing approach. Practical mixing and delivery of concrete could affect the properties of ready concrete due to prolonged time. In this paper, both the fly ash and fine fraction of recycled concrete were used to improve the quality of concrete due to coating of RCA, while the triple mixing technology was applied for this purpose. The compressive strength is evaluated from two aspects: the curing time (2, 28 and 90 days) and discharge time (0, 45 and 90 minutes after mixing) with attention being paid to the type of aggregate and the type of coating material. When using triple mixing technology, prolonged discharge time brings only small effect on the compressive strength (up to 12%) both in positive and negative way, depending on kind of coating material.