The Effect of Mineral and Chemical Admixtures on Fine Mortar Rheology


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Title: The Effect of Mineral and Chemical Admixtures on Fine Mortar Rheology

Author(s): P. Billberg

Publication: Special Publication

Volume: 173


Appears on pages(s): 301-320

Keywords: Cements; fineness modulus; mortars (materials); plastics, polymers and resins; shear properties; superplasticizers; yield strength; yield stress

Date: 9/1/1997

In this work a paste viscometer with concentric cylinders is used to evaluate the mineral- and chemical admixtures’ impact on fresh fine mortar rheology. Rheology results have been evaluated according to the Bingham model, which describes the rheology with the parameters; yield stress and plastic viscosity. Seven dolomite fillers have been investigated in combination with one superplasticizer and two cement types. The fillers originate from the same deposit, i.e. having the same mineralogy but different particle size distribution. Relationships have been established between rheology results and particle size analysis of cements and fillers. Increasing fineness leads to higher yield stress and plastic viscosity. Addition of superplasticizer results in a parallel displacement of these relationships towards lower rheology values. The results also show a significantly large difference in rheology depending on type of cement. Rheologically, the finer cement exhibits lower yield stress and plastic viscosity than the coarser cement, when adding the same amount of filler. The results for the reference mixes, when no filler is added, are the opposite. Rheology tests using a paste viscometer with concentric cylinders on the fine mortar part of the concrete is a effective method to describe additives’ influence on fresh concrete rheology.