Drying shrinkage rate

Fig. 4 Directional drying shrinkage rates of high-strength china billets...

It has been shown quantitatively (21) that the difference in shrinkage rates between the inside and outside of a drying body indeed results in a tensile drying stress. O. This tensile stress is a function of thickness, F ... 

Granulated iron is oxidised by the water and oxygen in the concrete and expands. This expansion can continue beyond the plastic phase and can therefore, in theory, counteract both settlement and drying shrinkage. In practice, it is difficult to achieve such precise control of the rate and duration of oxidation. 

Powdered aluminium normally mixed with find sand because of the low addition rate, reacts with the alkali to produce hydrogen. The expansion is completed during the plastic phase of the concrete and cannot therefore be used to compensate for drying shrinkage. 

Plastic shrinkage D Diagonal Roads and slabs Rapid early drying Low rate of bleeding 30 min to 6 h... 

The drying shrinkage of high-performance concrete is similar to that of normal concrete, but progresses much more slowly, owing to the reduced rate of drying. 

It may be expected that concrete adjacent to the outer surface of the vessel will lose moisture at a greater rate than in the general body of the vessel. This moisture gradient through the thickness of the vessel will cause differential drying shrinkage and the tensile stresses, hence, are introduced in the outer surface of the vessel. These stresses are effectively controlled by means of bonded reinforcement. 

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