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In this paper, a two-step model is proposed to predict the effective chloride diffusivity of cement paste and cement mortar. The prediction effective chloride diffusivity results of cement ...

The electrical resistivity of hardened cement-based materials was measured in this work by a modified noncontact electrical resistivity measurement (MN-CM). The resistivity was further proc...

Owing to its importance to the structural analysis and design of cement-based materials, it is essential to determine Young’s modulus of concrete. This paper presents a numerical method for predicting Young’s modulus of concrete with aggregate shape effect. In the numerical method, aggregate particles are assumed to be elliptical and distributed within a rectangular concrete element with periodic boundary conditions by introducing an overlap criterion for two elliptical aggregate particles. The method modifies the lattice model to take account of the mechanical properties of each phase constituent of concrete in the analysis of stress. After the validity of the developed numerical method is verified with three independent sets of experimental results, the effects of the maximum aggregate diameter, aggregate gradation, interfacial transition zone (ITZ) thickness, and aggregate shape on Young’s modulus of concrete are evaluated in a quantitative manner. It is found that Young’s modulus of concrete increases with the increase of the maximum aggregate diameter and aggregate aspect ratio but decreases by increasing the ITZ thickness. It is also found that the aggregate gradation has a significant influence on Young’s modulus of concrete. The paper concludes that the numerical method developed in the paper can predict Young’s modulus of concrete with an average relative error smaller than 7%.

Owing to their importance to the structural analysis and evaluation of cement-based materials, it is essential to determine the mechanical properties of cement paste. This paper presents a simple three-step analytical scheme for predicting the elastic moduli of hardened cement paste. In this scheme, hardened cement paste is modeled as a multiphase composite material, composed of unhydrated cement, C-S-H, CH, and capillary pores and further represented by five two-phase composite spheres. The elastic moduli of hardened cement paste are obtained in terms of the volume fractions and elastic moduli of unhydrated cement, C-S-H, CH, and capillary pores by the three-step scheme. Finally, the validity of the three-step scheme is verified with three independent sets of experimental data. The paper concludes that, when the water-cement ratio is in the range of 0.4–0.6, the simple three-step analytical scheme presented in the paper can predict the elastic moduli of hardened cement paste with an average relative erro...

This paper reports the results of experimental study on the effects of mineral admixtures such as silica fume, slag, fly ash, and metakaolin, on the mechanical behavior of young concrete under either uniaxial compression or tension. The uniaxial compression and uniaxial tension tests have been conducted on the concrete specimens at ages of 1/2, 1, 2, 3, 7, and 28 days. By utilizing the circumferential control and adaptive deformation control, the complete stress-strain (deformation) curves have been obtained for young concrete under either uniaxial compression or uniaxial tension. The experimental results show that the different mineral admixtures do have different influences on properties of young concrete. Metakaolin shows the best enhancement on the mechanical properties of young concrete generally.