The Effects of Superplasticizers on Plastic Shrinkage in Concrete

by ce on December 14, 2011

Superplasticizers, also called high range water reducers, are chemical admixtures that can be added to a concrete mixture to increase its workability or fluidity or even increasing it in the case of self consolidating concrete (SCC). These types of admixtures make it possible  to make a concrete with a reduced w/c ratio without affecting concrete’s workability. Even though the addition of superplasticizers in a concrete mixture is supposedly not to have negative effects on the properties of hardened concrete, the use of superplasticizers in a concrete mixture will likely affect the characteristic and/or properties of concrete in plastic state.
 
Some studies have been conducted to investigate the effects of superplasticizers on plastic shrinkage. In general the addition of superplasticizers will lower the risk of plastic shrinkage cracking. The amount of plastic shrinkage reduction will depend on the proportion and type of plasticizers used in the mixture.

Cabrera et al. reported that the surface tension capacity of a solution containing superplasticizers gives a good indication of the effectiveness superplasticizers in controlling the plastic shrinkage. The lower the tension capacity of the solution is, the more effective it is. It is also worth noting that the effectiveness of superplasticizers is strongly influenced by the dosage of superplasticizers.

 

References

ASTM C 260, Standard Specification for Air-Entraining Admixtures for Concrete, ASTM International, West Conshohocken, Pa., 2006.

ASTM C 494, Standard Specification for Chemical Admixtures for Concrete, ASTM International, West Conshohocken, Pa., 2006.

A. Kronlof, M. Leivo, P. Sipari, Experiment study on the basic of phenomena of shrinkage and cracking of fresh mortar, Cem. Concr. Res. 25(8) (1995) 1747–1754.

J.G. Cabrera, A.R. Cusens, B.Y. Wang, Effect of superplasticizers on the plastic shrinkage of concrete, Mag. Concr. Res., 44(160) (1992) 149–155.

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