The expansion property of cement mortar under the attack of sulfate ions is studied by experimental and theoretical methods. First, cement mortars are fabricated with the ratio of water to cement of 0.4, 0.6, and 0.8. Secondly, the expansion of specimen immerged in sulphate solution is measured at different times. Thirdly, a theoretical model of expansion of cement mortar under sulphate erosion is suggested by virtue of represent volume element method. In this model, the damage evolution due to the interaction between delayed ettringite and cement mortar is taken into account. Finally, the numerical calculation is results indicate that the model perfectly describes performed. The numerical and experimental the expansion of the cement mortar.
Under dynamic loading, the constitutive relation of the cement mortar will be significantly affected by the transversal inertial effect of specimens with large diameters. In this paper, one-dimensional theoretical analysis is carried out to determine the transversal inertial effect on the relaxation/retardation time of the cement mortar under the harmonic wave. Relaxation time or retardation time is obtained by means of the wave velocity, attenuation coefficient and the frequency of the harmonic wave. Thus, the transversal inertial effect on the relaxation time from Maxwell model, as well as on retardation time from Voigt model is analyzed. The results show that the transversal inertial effect may lead to the increase of the relaxation time, but induce the decrease of the retardation time. Those should be taken into account when eliminating the transversal inertial effect in applications.
Experimental results about concrete under sulfate attack are summarized, which include the variation of mass density of samples and velocity of ultrasonic wave propagating in samples. The evolution damage is analyzed in terms of the experimental results, and close attention is paid to the effect of damage evolution on Poisson＇s ratio. This study shows that Poisson＇s ratio is significantly affected by the concentration of solution and water-cement ratio. Poisson＇s ratio of concrete changes very little when the water-cement ratio is selected as 0.6 or 0.8, so that such change may be neglected. If water-cement is 0.4, however, the Poisson＇s ratio of the sample significantly changes. When the concrete sample of 0.4 water-cement ratio is immersed in sodium sulfate solution of 8% concentration for 285 days, Poisson＇s ratio increase 10.14% compared with its initial value. There exist a sensitive region and a non-sensitive region for the change rate of Poisson＇s ratio with respect to corrosion time. The change rate of Poisson＇s ratio monotonously decreases with corrosion time in the sensitive region; in the non-sensitive region, the change rate of Poisson＇s ratio is almost equal to zero.
