The modulus of elasticity of a concrete depends on the elastic stifness of both the cementitious matrix and the aggregate–ITZ
system, which includes any slippage mechanisms under loading between the aggregate and the cementitious matrix within the
interfacial transition zone (ITZ). A procedure is presented in this paper to estimate the elastic stifness of an aggregate–ITZ
system within a cementitious matrix, by considering the relative volumes and the porosities of the concrete components.
The method was validated by determining the elastic stifness of both the limestone–ITZ and the electric arc furnace slag
(EAFS)–ITZ systems when embedded in a slag-based cementitious matrix. The greater stifness of the EAFS–ITZ system
in comparison with the natural aggregate system explained the higher strength and modulus of elasticity of the concrete
following additions of EAFS. Moreover, having determined those parameters, the elastic moduli of concretes with a similar
cementitious matrix could then be accurately estimated.
