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Influence of Cement Particle-Size Distribution on Early Age Autogenous Strains and Stresses in Cement-Based Materials.


pdf icon Influence of Cement Particle-Size Distribution on Early Age Autogenous Strains and Stresses in Cement-Based Materials. (3799 K)
Bentz, D. P.; Jensen, O. M.; Hansen, K. K.; Olesen, J. F.; Stang, H.; Haecker, C. J.

Journal of the American Ceramic Society, Vol. 84, No. 1, 129-135, January 2001.

Keywords:

cements; particle size distribution; autogenous shrinkage; cement paste; eigenstress; hydration; pore size distribution; relative humidity

Abstract:

The influence of cement particle size distribution (PSD)on autogenous strains and stresses in cement pastes of identical water-to-cement ratio is examined for cement powders of four different finenesses. Experimental measurements include chemical shrinkage to quantify degree of hydration, internal relative humidity development, autogenous shrinkage, and eigenstress development using a novel embedded spherical stress sensor. Because the latter three measurements are conducted under sealed conditions, while chemical shrinkage measurements are made under "saturated" conditions, the National Institute of Standards and Technology cement hydration and microstructure development model is used to separate the effects of differences in hydration rates (kinetics) from those caused by the different initial spatial arrangement of the cement particles. The initial arrangement of the cement particles controls the initial pore-size distribution of the cement paste, which, in turn, regulates the magnitude of the induced autogenous shrinkage stresses produced by the water/air menisci in the air-filled pores formed throughout the hydration process. The experimental results indicate that a small autogeneous expansion (probably the result of ettringite formation), as opposed to a shrinkage, may be produced and early age cracking possibly avoided through the use of coarser cements.