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Adsorbing polymers and viscosity of cement pastes
Abstract In this paper, we study the physical mechanisms at the origin of a decrease in viscosity of concentrated cement pastes containing adsorbing polymers. We suggest from our results, similar to other authors, that plasticizers are able to decrease viscous dissipation by modifying the flocculation state of the system, which, in turn, impacts the way shear localizes. Our experimental results suggest that shear concentrates in fluid layers, the thickness of which scales with the surface-to-surface separating distance between cement grains imposed by the adsorbed polymer conformation. These effects being identical for all polymers, we suggest that the residual difference between polymers in the final macroscopic viscosity comes from the more or less pronounced increase in the local viscosity of the interstitial fluid between neighboring particles. This increase could either be correlated to the concentration of non-adsorbed coils in the interstitial fluid or to the local concentration of adsorbed coil side chains.
Highlights We measure adsorption and hydrodynamic radius of plasticizers. We measure the effect of various polymers on rheology of concentrated pastes. We correlate rheological measurements with molecular parameters. We measure the effect of various polymers on viscosity of interstitial solutions. We conclude on the role of the local viscosity of the inter-particle fluid.
Adsorbing polymers and viscosity of cement pastes
Abstract In this paper, we study the physical mechanisms at the origin of a decrease in viscosity of concentrated cement pastes containing adsorbing polymers. We suggest from our results, similar to other authors, that plasticizers are able to decrease viscous dissipation by modifying the flocculation state of the system, which, in turn, impacts the way shear localizes. Our experimental results suggest that shear concentrates in fluid layers, the thickness of which scales with the surface-to-surface separating distance between cement grains imposed by the adsorbed polymer conformation. These effects being identical for all polymers, we suggest that the residual difference between polymers in the final macroscopic viscosity comes from the more or less pronounced increase in the local viscosity of the interstitial fluid between neighboring particles. This increase could either be correlated to the concentration of non-adsorbed coils in the interstitial fluid or to the local concentration of adsorbed coil side chains.
Highlights We measure adsorption and hydrodynamic radius of plasticizers. We measure the effect of various polymers on rheology of concentrated pastes. We correlate rheological measurements with molecular parameters. We measure the effect of various polymers on viscosity of interstitial solutions. We conclude on the role of the local viscosity of the inter-particle fluid.
Adsorbing polymers and viscosity of cement pastes
Hot, Julie (author) / Bessaies-Bey, Hela (author) / Brumaud, Coralie (author) / Duc, Myriam (author) / Castella, Charlène (author) / Roussel, Nicolas (author)
Cement and Concrete Research ; 63 ; 12-19
2014-04-14
8 pages
Article (Journal)
Electronic Resource
English
Adsorbing polymers and viscosity of cement pastes
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