Abstract
Experimental tests have determined the effect of slag, opoka (silica-calcite sedimentary rock), silica fume (SiO2) suspension, dolomite dust and sodium silicate solution (NaSS) together with the polycarboxylatether based plasticizing admixture on the yield stress and viscosity of Portland cement paste the rheological properties of which have been defined applying a rotational viscometer with co-axial cylinders. The tests have revealed that slag, opoka, silica fume suspension and dolomite dust added to cement paste by replacing 10% of Portland cement (by weight) have an effect on the yield stress and viscosity of the paste subject to the form and fineness of additive particles. When 10wt% of Portland cement is replaced with slag cement, the yield stress of Portland cement paste reduces by about 25.9%, and viscosity increases by about 3.5 times compared with the yield stress and viscosity of reference cement paste. The yield stress of Portland cement paste with 0.5% NaSS admixture increases insignificantly, and viscosity grows approximately twice compared with reference cement paste. The tests have also showed that the modifying admixtures of Portland cement paste enable to control the rheological properties of cement paste.
Highlights
IntroductionThe possibilities of using alternative secondary materials that modify the rheological properties of concrete mixes as well as the physical and mechanical properties and structure parameters of hardened cement systems are explored in order to contribute to global climate protection and reduce the use of pure Portland cement clinker, the production of which causes environmental impacts at all stages of the process (Nochaiya et al 2010, Turk 2012, Grzeszczyk and Janowska-Renkas 2013, Hou et al 2013)
The possibilities of using alternative secondary materials that modify the rheological properties of concrete mixes as well as the physical and mechanical properties and structure parameters of hardened cement systems are explored in order to contribute to global climate protection and reduce the use of pure Portland cement clinker, the production of which causes environmental impacts at all stages of the process (Nochaiya et al 2010, Turk 2012, Grzeszczyk and Janowska-Renkas 2013, Hou et al 2013).Both yield stress and viscosity are strongly dependent on the particle characteristics of the powders employed in preparing a blended cement/ fly ash paste with a constant volume fraction of water
The curves in the figure show that the flow curve of Portland cement paste with cement CEM I 42.5 N and the plasticizing admixture added at 0.5wt% (Composition I) is not linear, as in the Bingham plastic model, but has a shape of a curve
Summary
The possibilities of using alternative secondary materials that modify the rheological properties of concrete mixes as well as the physical and mechanical properties and structure parameters of hardened cement systems are explored in order to contribute to global climate protection and reduce the use of pure Portland cement clinker, the production of which causes environmental impacts at all stages of the process (Nochaiya et al 2010, Turk 2012, Grzeszczyk and Janowska-Renkas 2013, Hou et al 2013) Both yield stress and viscosity (apparent or plastic) are strongly dependent on the particle characteristics of the powders employed in preparing a blended cement/ fly ash paste with a constant volume fraction of water. Viscosities are influenced by both cement and fly ash particles, with approximate linear relationships between plastic viscosity values and either total particle surface area or total particle density being found (Bentz et al 2012, Perrot et al 2012)
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