Viscoelasticity of Solidifying Porous Material°Concrete

by Zdeněk P. Bažant, (M.ASCE), Prof.; Northwestern Univ., Evanston, Ill., and Visiting Scientist, Swedish Cement and Concrete Inst. (CBI), Royal Inst. of Tech., Stockholm, Sweden,

Serial Information: Journal of the Engineering Mechanics Division, 1977, Vol. 103, Issue 6, Pg. 1049-1067

Document Type: Journal Paper


The form of the age effect on linear creep and elasticity is established by treating the hydrating cement paste as a variable composite in which the volume fraction of solid grows while the material creeps under load. The formulation rests on three hypotheses: (1)The average strains in microelements solidified at various times are equal; (2)the properties of solidified matter (cement gel) are time-invariant; (3)the rate of migrations of solid particles causing creep in cement gel depends on the mean length of migration passages at the time of load application. The first hypothesis allows eliminating the microstresses from a system of two integral equations set up to relate stress and strain histories. A new form of the creep function is deduced, expressing the aging effect in terms of the growth of volume of cement gel and the increase of the migration passage length. It is shown that the double power law is obtained as a special case when the growth of gel volume is negligible, and a generalization consistent with growing gel volume is suggested and compared with creep data.

Subject Headings: Porous media | Creep | Cement | Viscoelasticity | Solidification | Aging (material) | Composite materials | Load factors

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