The effect of viscosity modifying agents on mortar and concrete

Abstract The influence of different viscosity modifying agents (VMA) on the flow properties and the rheology of self-compacting mortars is studied. Additionally, their effect on the early hydration of cement pastes and on the development of concrete strength is determined. Beside the inorganic VMA microsilica (MS) and nanosilica slurry (NS) organic VMA based on high molecular ethylenoxide derivate (EO), natural polysaccharide (PS) and starch derivate (ST) are used. The different VMA are combined with a superplasticizer (SP). At constant water-to-binder ratio (w/b) the addition of VMA causes a decrease of mortar flow and an increase of flow time (V-funnel test). At the same time yield stress and plastic viscosity are increased. At a constant dosage of superplasticizer (SP) mixtures with VMA require a higher w/b to keep the same flow properties as the reference mixtures without VMA. In spite of the higher w/b flow time and plastic viscosity respectively are only slightly reduced. This property is especially beneficial for the production of stabilizer-type self-compacting concrete where the amount of fines can be reduced with the use of VMA. However, only the use of VMA PS and ST leads to smaller changes of flow when w/b is changed. The organic VMA show almost no influence on early cement hydration and the development of compressive strength. However, the inorganic VMA cause an acceleration of hydration and higher compressive strength at the age of 1 day.

[1]  M. Müller,et al.  Rheologische Charakterisierung von Maschinenputzen , 1999 .

[2]  Hajime Okamura,et al.  Self-Compacting Concrete , 2000 .

[3]  W Kusterle,et al.  Rheology and rebound behaviour of dry-mix shotcrete , 2001 .

[4]  A. Neville.  Properties of Concrete , 1968 .

[5]  K. Khayat,et al.  USE OF VISCOSITY-MODIFYING ADMIXTURE TO ENHANCE STABILITY OF FLUID CONCRETE , 1997 .

[6]  Mohamed Lachemi,et al.  Performance of new viscosity modifying admixtures in enhancing the rheological properties of cement paste , 2004 .

[7]  J. Hjorth,et al.  29Si MAS NMR studies of portland cement components and effects of microsilica on the hydration reaction , 1988 .

[8]  M. Sari,et al.  High strength self-compacting concrete Original solutions associating organic and inorganic admixtures , 1999 .

[9]  M. Schatzmann,et al.  Rheological behavior of fine and large particle suspensions , 2003 .

[10]  Kamal H. Khayat,et al.  Viscosity-enhancing admixtures for cement-based materials — An overview , 1998 .

[11]  Mohamed Lachemi,et al.  Development of Cost-Effective Self-Consolidating Concrete Incorporating Fly Ash, Slag Cement, or Viscosity-Modifying Admixtures , 2003 .

[12]  Victor C. Li,et al.  Design of Engineered Cementitious Composite Suitable for Wet-Mixture Shotcreting , 2003 .

[13]  M. Collepardi,et al.  Self-Compacting Concrete: What Is New? , 2003, SP-217: Seventh CANMET/ACI International Conference on Superplasticizers and Other Chemical Admixtures in Concrete.