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h i g h l i g h t sInfluence of mixing intensity on rheological behaviors of cement paste was assessed. High mixing intensity can result in increasing the rheological properties. Plasticized pastes were more sensitive to effect of mixing intensity than non-plasticized pastes. Cement pastes prepared using high mixing intensity can be more agglomerated than pastes prepared using low mixing intensity. Effects of the mixing intensity also affected hydration. a b s t r a c tMixing is one of the most important processes for producing concrete. The influence of different mixing methods on the rheological properties and fresh state microstructure of cement pastes were evaluated. In this work, the mixing process of cement paste was based on two different sample preparation methods: ASTM C305 and ASTM C1738. ASTM C1738 uses a high shear mixer, whereas ASTM C305 uses a planetary mixer to homogenize cement paste. A considerable increase in the rheological properties was seen in pastes prepared using the ASTM C1738 protocol versus those prepared according to ASTM C305, especially when a superplasticizer was incorporated. Not only were the rheological properties affected, but differences in hydration kinetics and fresh state microstructure were also observed, with mixtures prepared with ASTM C1738 generally displaying more flocculated microstructural features and accelerated hydration kinetics than mixtures prepared with ASTM C305.

From both the fundamental and applied points of view, there is a growing interest in characterizing the rheological properties of concentrated suspensions, such as cement paste. When a cement paste is sheared, its intrinsic network structure will respond to the shear induced stresses. The influence of mixing intensity on the rheological properties of fresh state cement paste is studied. The results showed that contrary to what is popularly believed, when subjected to a high mixing intensity the rheological properties of cement paste can increase once a certain threshold mixing intensity is achieved. This increase in rheological properties was associated with changes in the chemical nature and physical nature of the cement pastes.

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Various factors influence the rheology of cementitious pastes, with the most important being the mixing protocol, mixture proportions, and mixture composition. This study investigated the influence of ground-granulated blast-furnace slag, on the rheological behavior of cementitious pastes. In tandem with the rheological measurements, fresh state microstructural measurements were conducted using three different techniques: A coupled stroboscope-rheometer, a coupled laser backscattering-rheometer, and a conventional laser diffraction technique. Laser diffraction and the coupled stroboscope-rheometer were not good measures of the in situ state of flocculation of a sample. Rather, only the laser backscattering technique allowed for in situ measurement on a highly concentrated suspension (cementitious paste). Using the coupled laser backscattering-rheometer technique, a link between the particle system and rheological behavior was determined through a modeling approach that takes into account agglomeration properties. A higher degree of agglomeration was seen in the ordinary Portland cement paste than pastes containing the slag and this was related to the degree of capillary pressure in the paste systems.