PROPERTIES OF CEMENT PASTE

Neubauer, C.M. (1997) On the Chemistry, Micro structure, and Deformation Properties of Cement Pastes Towards a New Strategy for Controlling Drying Shrinkage. PhD. Thesis, Northwestern University. 

Water having harmful ingredients, contamination, silt, oil, sugar or other chemicals is destructive to the strength and setting properties of cement paste and might adversely effect the workability of a mix. 

In determining the resistance to degradation of concrete and its role in protecting the embedded steel, not only should the total capillary porosity (i. e. the percentage of volume occupied by capillaries) be considered but also the size and intercormec-tion of capillary pores. Figure 1.6 shows the relation between the transport properties of cement paste (expressed as coefficient of water permeabihty) and the compressive strength as a function of the w/c ratio and degree of hydration [7]. 

Zivica, V., The Properties of Cement Paste with Admixture of Polyvinyl Acetate Emulsion, Bulletin RILEM, No. 28, pp. 121-128 (Sept. 1965)... 

Clinker phase composition has decisive influence on several properties of cement paste, thus also on concrete. The most important are the following ... 

The tricalcium aluminate reacts with water at a highest rate among the clinker phases and affects substantially the rheological properties of cement paste. The gel products are formed very rapidh and subsequently crystalhze as a mixture of the two phases C2AHg and C4AHJ3 respectively. These products cover the C3A grains and further... 

There are several hypotheses as the rheological properties of cement pastes are concerned. As it is commonly known the rheology deals with the flowing and deformation of materials imder stress. The Newtonian fluids show a simple relationship between the shear stress and shear rate. When a thin layer of fluid is placed between the two parallel plates, of which one is fixed and the second will be subjected to the shearing force F, then the shearing of this layer will occur. The dynamic equilibrium will be attained when the force F, in the condition of stationary flow, will be balanced by the viscosity of Newtonian fluid and the relation between the shear stress and shear rate gradient will be linear (Fig. 5.1). 

As it was aforementioned, the rheological properties of cement pastes are dependent on many factors. In Fig. 5.7 the evolution of the properties of pastes from the pseudoplastic fluids through the Bingham fluid to the showing dilatancy, at higher... 

The water to cement ratio and the fineness of cement are the two important factors determining the properties of cement paste. The thickness of water layer on cement grains and the distance between the grains are dependent upon these parameters, which have the significant effect on the rheological properties of paste, first of all on the yield stress value. 

The analysis of the rheological properties of cement pastes is complicated additionally by the interaction of solid and liquid phase. In Table 5.1 the approxiniate size of hydrating cement grains and the distances attributed to the particular types of interactions are shown according to Massazza [21],... 

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