Optimizing mix‐proportions for flowable high performance concrete via mortar rheology

Abstract

Rheology of flowable high performance concrete(HPC) is pretty much governed by the viscous property of its cement paste. In other words, the flowability of mortar determines the movability of coarse aggregates in a fresh concrete, less friction along interfaces of coarse aggregate enhances smoother flow of fresh concrete. Our experimental study concluded that a proper rheological range and suitable mortar thickness coating on coarse aggregate collectively control the flow of high performance concrete. Based on Newton's viscous flow law and the mortar overfill/coating thickness, a series of test programs using mix proportions that yielded 60 cm slump flow were carried out to determine the relationship between the flowability of mortar and the volumetric fraction of coarse aggregate used. In addition, mortars made with 12 mix proportions similar to those used in the concrete mixes having 600 mm slump flow were carried out to verify the validity of the test results obtained in the concrete test series. This report describes the test program along with test data and findings on optimizing mix proportions for production of flowable high performance concrete.