No abstract

No abstract

IJ.in which e v, cr v = volumetric strain and stress; superscript V refers to volumetric component; 0' V , 0' V = hidden volumetric stresses in solids (subscript s) and in water (subs~ript w~); K~, K: = (tangent) elastic bulk moduli ~f solids a~d water associated with the hidden stresses; es(h) = instantaneous shrInkage stram depending on the relative humidity, h, in the capillary pores (macropores) within the material'coefficients associated with the , '+'ss ... ' "+'swlL' "+'wsv-' '+'ww.., • • • microscopic diffusion fluxes of solids (s) and water (w), and theIr mutual couphng, O'h = functions of h = values of hidden stresses in hindered adsorbed water la~ers that would be necessary for thermodynamic equilibrium with the adjacent capillary pore:; containing water vapor of humidity h (see Ref. 4); zero value of O'h is chosen at h = 1; and the dots refer to the derivatives with respect to ti~e t; e.g., E = del dt. Eqs. la, lb, and 2 can be applied only for the stress range in which microcracking is negligible, i.e., when stresses are less EM6 CREEP AND SHRINKAGE 1185

Development of conceptual and mathematical models describing the corrosion of steel in prestressed concrete is outlined. The application of the principles of stress corrosion and general corrosion to understanding the mechanisms involved in corrosion of steel in prestressed concrete is discussed. The first step in estimating the failure time of a prestressed concrete structural system because of corrosion of the reinforcing steel is to estimate corrosion rates under various realistic conditions. A simplified approach based on mathematical modeling of concrete properties for estimating corrosion rates is proposed.Before the proposed mathematical model can be applied to practical problems information is needed on the specific mechanisms of corrosion cell processes of steel in prestressed concrete.In addition, well designed corrosion tests need to be performed in which the important factors affecting the corrosion rates are considered.

No abstract