Suspended hydration and loss of freezable water in cement pastes exposed to 90% relative humidity

Abstract Degree of hydration (DOH) and differential scanning calorimetry (DSC) measurements are used to characterize the effect of early exposure to a 90% relative humidity (RH) environment on cement paste hydration. Early exposure to a 90% RH environment can lead to the consumption of freezable water and altered microstructural development. The minimum duration of 100% RH curing required to eliminate the effects of an unsaturated environment on microstructural development coincides with the appearance of a DSC peak near −30 °C that occurs in the range 1–14 days for the pastes studied. The Jennings colloidal microstructural model is used to argue that the −30 °C peak coincides with the cessation of capillary pore percolation. Alternatively, all samples cured under 100% RH conditions for 7 days prior to 90% RH exposure hydrated at the same rate as those continuously exposed to 100% RH. The application of these results to the formulation of separate curing practices for durability and strength is discussed.

[1]  I. Odler,et al.  Investigations on the relationship between porosity, structure and strength of hydrated portland cement pastes I. Effect of porosity , 1985 .

[2]  H. Jennings,et al.  A model for two types of calcium silicate hydrate in the microstructure of Portland cement pastes , 2000 .

[3]  Thompson,et al.  Quantitative prediction of permeability in porous rock. , 1986, Physical review. B, Condensed matter.

[4]  C. Jackson,et al.  The melting behavior of organic materials confined in porous solids , 1990 .

[5]  Edward J. Garboczi,et al.  The effect of statistical fluctuation, finite size error, and digital resolution on the phase percolation and transport properties of the NIST cement hydration model , 2001 .

[6]  Will Hansen,et al.  Volume Relationships for C-S-H Formation Based on Hydration Stoichiometries , 1986 .

[7]  R. Evershed,et al.  Mat Res Soc Symp Proc , 1995 .

[8]  P. Baglioni,et al.  A novel approach based on differential scanning calorimetry applied to the study of tricalcium silicate hydration kinetics , 2002 .

[9]  A. Adamson.  Physical chemistry of surfaces , 1960 .

[10]  Dirch H. Bager,et al.  Ice formation in hardened cement paste, Part I — room temperature cured pastes with variable moisture contents , 1986 .

[11]  D. Macphee,et al.  Polymerization effects in C-S-H: implications for Portland cement hydration , 1988 .

[12]  Hamlin M. Jennings,et al.  A model for the microstructure of calcium silicate hydrate in cement paste , 2000 .

[13]  Nicholas J. Carino,et al.  Applicability of the maturity method to high-performance concrete , 1992 .

[14]  Hamlin M. Jennings,et al.  Model for the Developing Microstructure in Portland Cement Pastes , 1994 .

[15]  S. Chandra,et al.  10th International congress on the chemistry of cement , 1997 .

[16]  Bertil Persson,et al.  Self-desiccation and its importance in concrete technology , 1997 .

[17]  I. Odler,et al.  Investigations on the relationship between porosity, structure and strength of hydrated Portland cement pastes. II. Effect of pore structure and of degree of hydration , 1985 .

[18]  L. Struble,et al.  Microstructural development during hydration of cement , 1987 .

[19]  G. R. Gause,et al.  Method for determining the moisture condition in hardened concrete , 1940 .

[20]  Edward J. Garboczi,et al.  Percolation of phases in a three-dimensional cement paste microstructural model , 1991 .

[21]  J. W. Little,et al.  The NBS Two-Pressure Humidity Generator, Mark 2 , 1977, Journal of Research of the National Bureau of Standards. Section A, Physics and Chemistry.

[22]  Göran Fagerlund,et al.  Determination of pore-size distribution from freezing-point depression , 1973 .

[23]  E. Sellevold,et al.  Ice Formation in Hardened Cement Paste—1. Mature Water-Saturated Pastes , 1980 .

[24]  T. Powers,et al.  A DISCUSSION OF CEMENT HYDRATION IN RELATION TO THE CURING OF CONCRETE , 1948 .

[25]  E. J. Sellevold,et al.  Ice formation in hardened cement paste, Part II — drying and resaturation on room temperature cured pastes , 1986 .

[26]  L. Pel,et al.  Combined NMR cryoporometry and relaxometry , 2002 .

[27]  C. W. Richards,et al.  Effect of freezing on the dynamic mechanical response of hardened cement paste down to −60°C , 1972 .