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Based on the small density changes of each phases, the defects and morphology of cement-based materials can be observed with the X-ray computed tomography (X-CT). The application of X-CT technology in the cement-based materials was reviewed in this paper. The microstructural changes during processes of carbonation, corrosion and steel corrosion were observed with X-CT equipment. It showed that the resolution of X-CT technology was limited and can up to 20um when the sample is small enough. The distribution of fibers, the pore structures and the cracks could be observed with 2D/3D images, and statistical information could also be calculated by the software. So the X-CT equipment played an important role in the strengthening and toughening mechanism analysis of fiber-reinforced concrete, porosity calculations and antifreeze analysis of general concrete and air-entrained concrete. The structural changes of concrete under the conditions of service, after carbonation, dissolution and steel corrosion could also be observed clearly.

Water-reducer is one of the dispensable components in modern concrete, can improve the workability and mechanical performance of concrete, and also has an important influence on the plastic cracking resistance of concrete. In this paper, the flat cracking test was used to evaluate the effect of water reducer on the plastic cracking resistance of concrete, meanwhile, capillary pressure; plastic settlement and evaporation rate were also tested. The results showed that water-reducer could improve the plastic cracking resistance of concrete significantly, and the effectiveness of polycarboxylate water reducer were o better than that of wood calcium and naphthalene water reducer.

As a novel conductive elastomer, magnetorheological elastomers (MREs) featuring both high sensitivity and wide working range have been employed as a new sensing material for flexible tactile sensors. Their sensing mechanism, that is, the spatial distribution rearrangement of particles under compression, completely differs from their conventional counterparts. The piezo-capacitive effect of MREs resulting from the unique mechanism of particles rearrangement is actually a response to the microscopic mechanical movement of particles. This nature brings a core concern on the intrinsic relationship between their mechanical and electrical properties. This study illuminates them from the perspective of electrical creep and recovery behavior of MREs. We give a meaningful analysis for the capacitance creep-recovery mechanism. The experimental fact strongly demonstrated that the particles rearrangement was the direct cause, while the strain creep was an indirect cause. All the behaviors were well interpreted by an evolution mechanism of the particles rearrangement driven by the mechanical strain creep of the flexible matrix under constant pressure. In simpler terms, the electrical creep was induced by the mechanical creep. We further explored the creep effect in practical applications and found a “self-healing” behavior, which indicated that the MRE sensors could obtain a stable sensing capability after a pre-processing.