STRENGTH DEVELOPMENT IN HARDENED CEMENT PASTE - EXAMINATION OF SOME EMPIRICAL EQUATIONS

A number of empirical expressions are frequently used to describe or p redict the strength of normal hardened cement paste. The more well-kno wn expressions of Balshin, Hasselman and Ryshkewitch relate strength a nd porosity. The Bolomey formula relates strength and water/cement rat io. All these expressions are shown to be theoretically well justified . They are pore-specific versions of a more general expression present ed in this paper. The Balshin expression is suggested to be in general the better strength porosity relation. Bolomey's formula is shown to be a logical numerical consequence of this statement. Parameters are g iven for both these relations which depend on degree of hydration. The Ryshkewitch expression applies strictly only at vanishing porosity. L ow-porosity strengths are overestimated by the Ryshkewitch expression when calibrated (fitted) to experimental data at finite porosities.