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Concrete is the most widely used building material in civil infrastructure in the world, but because its hydrophilic and porous surface structure promotes the penetration of water and the erosion of corrosive ions, the concrete is damaged by freezing and melt, expansion and denudation, which leads the safety and durability of concrete structure to seriously reducing. Superhydrophobic surfaces have good water resistance and can be applied to concrete, coating or overall superhydrophobic concrete has received considerable attention in the last decade, and also has a good application value in the field of anticorrosion and ice prevention. In this context, this paper first briefly summarizes the basic wettability model for concrete concrete cases. Secondly, we review the existing advanced strategies for constructing superhydrophobic concrete, mainly divided into surface hydrophobic modification and overall hydrophobic modification, and summarize the advantages and disadvantages of two different strategies. When the concrete is in the extreme environment such as cold and marine environment, it is particularly important to improve the anti-corrosion and ice prevention performance of the concrete, so the influence of the water modification is discussed in this paper. In addition, the theoretical basis of superhydrophobic modification technology for concrete corrosion and ice is briefly described. Finally, the challenges in the current fabrication and application of superhydrophobic concrete and the potential solutions to these problems are indicated. [ABSTRACT FROM AUTHOR]

As an artificial cement based material, cemented tailings backfill (CTB) has significant loading rate (LR)effect, and its deformation and failure are closely related to acoustic emission(AE)characteristics. To study the mesoscopic AE characteristics of the backfill under different LRs, a series of uniaxial compressive strength (UCS) tests with different LRs were carried out for CTB The strength evolution law was determined. With the aid of Particle Flow Code(PFC2D), the crack evolution and mesoscopic AE characteristics of the backfill were analyzed from the mesoscopic point of view. Combined with the theory of energy conservation, the LR effect of the backfill was discussed. The results show that: 1) The uniaxial compressive strength of backfill was positively correlated with the LR, and the relationship between them was a quadratic polynomial function. 2) The numerical simulation results showed that increasing the LR increased the crack initiation stress of the backfill, advanced the crack initiation time and increased the total number of cracks after failure. In addition, with the increase of the LR, the failure mode of the backfill gradually changed from shear failure to tension shear mixed failure. 3)The mesoscopic AE event time step curve experienced initial period, calm period, slow rise period, rapid rise period and rapid decline period, which was highly consistent with the AE characteristics obtained from the test. There were few AE events before the peak, and the AE event dense zone was not obvious. After the peak, AE events and AE events with larger magnitude increase rapidly, forming interconnected AE dense zone. 4) The boundary energy, strain energy and dissipation energy were positively correlated with the LR. The higher LR had a certain blocking effect on the crack initiation and propagation of the backfill, which increased the energy storage limit of the sample, and then improved the strength performance of the backfill. However, the higher energy accumulation before the peak will also lead to the rapid release of energy in the post peak stage, the rapid propagation of cracks, the formation of large mesoscopic damage and the increase of the cumulative number of cracks in the sample. The results can provide reference for the study of the LR effect and mesoscopic AE characteristics of the backfill. [ABSTRACT FROM AUTHOR]

Under loading and environment, the cracking will easily occur and reduces the durability and strength of the structure concrete. Inspired by the capsule-based self-repairing system, a self-healing system of repairing agent to be encapsulated in the porous lightweight aggregates that are used as carriers was proposed. In the paper, the recent progresses of lightweight aggregates self-repairing cementitious materials are reviewed and the rupture mode of inorganic porous lightweight aggregates and the mechanism of repairing agent to be released are described. The mechanical properties and durability of the cementitious matrix are compared before and after the repairing process and the evaluation methods of crack-repairing degree and repairing efficiency are also discussed. Finally, the key problems and the research direction of lightweight aggregate self-repairing cementitious material are summarized. [ABSTRACT FROM AUTHOR]