Title: Analysis of the Effect of Three-Stage Mixing on the Properties of Concrete with Recycled Aggregates and Various Mineral Additives

Author(s): Alena Sicakova

Publication: Symposium Paper

Volume: 355

Issue:

Appears on pages(s): 455-464

Keywords: recycled concrete aggregate; cement; fly ash; recycled concrete powder; recycled aggregate concrete; three-stage mixing; compressive strength, prolonged mixing time

DOI: 10.14359/51736053

Date: 7/1/2022

Abstract:
The use of recycled concrete aggregate, as a component of the new concrete mixture, implies a thorough understanding of its basic properties, considering that they may significantly differ from the properties of natural aggregates. It is believed that its performance can be enhanced by improving the surface properties of RCA. Coating RCA grains within a triple mixing process represents one of the promising methods. This principle has been adopted by several researchers who report a significant improvement in concrete properties compared to standard mixing, especially through improved ITZ parameters. In the paper, the triple mixing process of concrete with coarse RCA was studied, while the method of applying the mineral powdery materials (cement, fly ash, and fine particles of RCA) to the pre-moistened aggregate was used. A comparison of positive/negative effects of three-stage mixing on the set of six properties of concrete, comparing standard mixing is presented. It was found that three-stage mixing has no different effect on samples prepared after prolonged mixing than on samples prepared immediately after mixing, nor on samples cured for 90 days than on samples cured 28-days. Cement as a coating material gave the best results in the presented range of testing while RCA powder showed promising potential.