Most concrete structures and buildings are under temperature and moisture variations simultaneously. Thus, the moisture transport in concrete is driven by the moisture gradient as well as the temperature gradient. This paper presents an experimental approach for determining the effect of different temperature gradients on moisture distribution profiles in concrete. The effect of elevated temperatures under isothermal conditions on the moisture transport was also evaluated, and found not to be significant. The non-isothermal tests show that the temperature gradient accelerates the moisture transport in concrete. The part of increased moisture transfer due to the temperature gradient can be quantified by a coupling parameter D_HT, which can be determined by the present test data. The test results indicated that D_HT is not a constant but increases linearly with the temperature variation. A material model was developed for D_HT based on the experimental results obtained in this study.

This study investigated compressive strength, chloride penetration, and freeze-thaw resistance of multiwalled carbon nanotube (MWNT) concrete. More than 100 cylindrical specimens were used to assess test variables during sensitivity observations, including water-cement ratios (0.75, 0.5, and 0.4) and exposure to chemical agents (including gum arabic, propanol, ethanol, sodium polyacrylate, methylcellulose, sodium dodecyl sulfate, and silane). To determine the adequate sonication time for MWNT dispersal in water, the compressive strengths of MWNT concrete cylinders were measured after sonication times ranging from 2 to 24 minutes. The results demonstrated that the addition of MWNT can increase the compressive strength of concrete by up to 108%. However, without chemical treatment, MWNT concretes tend to have poor freeze-thaw resistance. Among the different chemical treatments, MWNT concrete treated with sodium polyacrylate has the best compressive strength, chloride resistance, and freeze-thaw durability.

Prediction of the elastic properties of cementitious materials has been the aim of many researchers. This study developed a new multiscale and multiphase model based on the Mori-Tanaka method for predicting effective elastic properties of hardened cement paste, such as modulus of elasticity. The model considered the microstructural variation in and nonspherical morphology of the hydration products in hardened cement paste. In order to improve prediction accuracy, the model included the effect of ettringite on the elastic properties in addition to the other major hydration products. Instead of considering cement clinker as an isotropic and homogeneous material, this study simulated the clinker as a four-phase composite. In addition, the model used a matrix-inclusion configuration that can include the clinker and ultra-high-density calcium silicate hydrate. Another improvement is that a weakened matrix-inclusion interface was introduced using the modified Eshelby tensor. The prediction results of the model were compared with the experimental data, and good agreement was obtained.