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Hydration-kinetics and Water Content of Cement Quasi-Elastic Neutron Spectroscopy Studies

Norbert M. Nemes

Center for Neutron Research, MSEL

Dan A. Neumann

Center for Neutron Research, MSEL

Richard A. Livingston

Office of Infrastructure R&D,

Federal Highway Administration, McLean, VA 22101

Abstract

Portland cement is a complex non-homogeneous material, with many different constituent phases and structure over a wide range of length scales. The hydration of Portland cement is a complex process involving several simultaneous chemical reactions. All of these reactions involve water, and as hydration proceeds, more of the water that is initially mixed with the cement powder becomes chemically bound into reaction product phases. Quasi-elastic neutron scattering (QENS) allows for the study of the state of water in hydrating cement paste in-situ over time and over a wide range of temperatures. QENS provides a direct measure of the conversion of free water to structurally/chemically bound water and to water constrained in the pores of the cement paste.

We studied the hydration kinetics of synthetic cement paste with varying alite/belite (dicalcium silicate or C2S and tricalcium silicate or C3S) and varying water/cement ratios. The time-dependent free, constrained and bound water results are analyzed in terms of the Avrami-model for the nucleation and growth regime and in terms of a diffusion-limited growth model for the later period. The results reveal the complex nature of the chemistry governing the hydration of cement as the dependence of the model parameters on the C2S/C3S ratio is highly non-linear.
 
 
 
 
 
 
 
 
 
 
 
 

Norbert M. Nemes

Center for Neutron Research

MSEL

Bldg. 235 Rm. E18

MS8565

Phone: 301-975-8829

Fax: 301-921-9847

nemes@nist.gov

Not Sigma Xi member

Category: Materials