The delayed thermal dilatation of cement paste and concrete is caused by the diffusion of molecules of water and other species along mono- or multimolecular layers. Applying thermodynamics to this diffusion mechanism, the macroscopic constitutive equation is derived for the case of constant water content. Three different components of thermal dilatation are distinguished: (1) pure thermal dilatation, due to thermal dilatation of constituents; (2) thermal shrinkage or swelling, due to differences in latent heat (and entropy) along the diffusible layers; (3) hygrothermic dilatation, due to a change in relative vapor pressure with temperature at a constant water content. The first two components lead to delayed recovery while the third one results in continued delayed thermal dilatation. The dependence of these components on the water content is discussed. The theory is important for the thermoviscoelastic analysis of prestressed concrete reactor pressure vessels.
ASJC Scopus subject areas
- Mechanical Engineering
- Nuclear and High Energy Physics
- Safety, Risk, Reliability and Quality
- Waste Management and Disposal
- General Materials Science
- Nuclear Energy and Engineering