Assessment of Rheology Variations of Cement Pastes Containing Clinker Grinding Aids Compliant With ASTM C465

Abstract

Abstract ASTM C465 (Standard Specification for Processing Additions for Use in the Manufacture of Hydraulic Cements, ASTM International, West Conshohocken, PA, 2010,www.astm.org) is widely used in the cement industry to evaluate variability of cement properties as a result of the addition of grinding aids (GAs). The standard specifies a series of physical and chemical tests to determine whether such additions detrimentally affect cement properties; however, it refrains from considering their effects on rheological properties. This paper seeks to assess the variations in yield stress (τ0) and viscosity (η) of cement pastes containing GAs compliant with ASTM C465. Three series of cement mixtures were ground for different Blaine fineness of 2880, 3460, and 4420 ± 100 cm2/g using various concentrations and types of GAs. Regardless of Blaine and GA type, the addition of increased GA concentrations leads to improved flowability together with reduced τ0 and η responses. For dosage rates satisfactory fulfilling ASTM C465, the variations of such responses with respect to control values obtained using cement ground without GA were found to reach −25 %, −30 %, and −40 % when clinker is ground with amine-, glycol-, and phenol-based GAs, respectively. The variations in τ0 and η are independent of the water-to-cement ratio, but tend to increase for higher GA concentration and increased cement fineness. Four threshold regions corresponding to −10 %, −20 %, −30 %, and −40 % were suggested to evaluate adaptability of ASTM C465 to reflect changes in rheological properties.