Mixing of Concretes with Extremely Low Water-Cement Ratio

摘要

This article deals with the ways of mixing method for concrete with extremely low water-cement ratio (w/c) typical for ultra-high performance concretes. For this purpose, the mixture with w/c ratio of 0.2 and amount 6% superplasticizers of cement weight was used. In total 6 various mixing methods was tested, which differed in application of superplasticizers, mixing order or mixing length. Workability, electricity consumption during mixing and compressive and flexural strength after 28 days were examined. The performed experiments showed that workability can be increased by, for example, separate doses of superplasticizers and water or other mixing methods. Strength of concrete was identical for all produced mixtures, even though the total mixing time was shortened in two cases.