Experimental Study on the Novel Interface Bond Behavior between Fiber-Reinforced Concrete and Common Concrete through 3D-DIC

A novel method was proposed to improve the bond behavior of new-to-old concrete interface, which was beneficial to introduce the fiber-reinforced concrete only at the old concrete interface. This study investigated the effect of the fiber addition, strength grade of new concrete, interfacial angle, and surface treatment types on the bond behavior in terms of the new-to-old concrete through the axial tensile tests. The three-dimensional digital image correlation technique (3D-DIC) and scanning electron microscope were adopted to evaluate the variation of specimen surface strain distributions and microstructure of fiber-reinforced concrete and bond interface between new-to-old concrete. The experimental results indicated that interfacial angle and surface treatment type were significantly promoted bond behaviors, while the specimen cooperating with steel fibers had the highest bond strength. Besides, the maximum strain locations obtained from 3D-DIC method were the same as the location of the specimen failure, which indicated the 3D-DIC method can be adopted to forecast the structural failure. The microcrack strain located in the major crack was decreased with the development of the major crack. Ample crystals and Ca(OH)2 were generated in the interface between the new-to-old concrete to weaken the bond strength. Moreover, this paper provided the mechanics-driven and machine learning method to predict the bond strength. This study provides a new interface bonding method for the fabricated and large span structure to effectively avoid cracking of new-to-old concrete.

Study of the Change in the Coal-and-Liquid-and-Gas Interfacial Angle

The use of surfactants has a significant impact on the safety of mining operations in order to prevent dynamic processes, prevent dust. The interfacial angle is the main indicator characterizing the interfacial interactions for heterogeneous multicomponent solid bodies, coal and solutions. The problem of development of modern methods for determining the interfacial angle at the coal-water-gas boundary is considered. The results of the research study of the change in the coalliquid-gas interfacial angle are presented. The influence of various coal properties and characteristics on the interfacial angle value is shown. The influence of the interfacial angle on wetting and filtration processes, the features of the experimental methods for the interfacial angle determination are shown. A model of the coal surface consisting of four main components is proposed. The main attention is paid to the moisture content of coal and capillaries as the main factors determining the properties of coal. An analytical method for determining the interfacial angle of coalwater-gas is proposed.

Study of dispersion of boron nitride nanotubes by triton X-100 surfactant using molecular dynamics simulations

In this study, the dispersion of aggregated boron nitride nanotubes (BNNTs) in aqueous triton X-100 surfactant solution is studied using molecular dynamic simulation. The results indicate that how in the presence of the surfactant, a space between two BNNTs is created, which leads to the dispersion of the BNNTs. The radial distribution functions (RDFs) of the atoms of BNNTs and hydrophilic and hydrophobic segments of the surfactant respect to atoms of water molecules show that in the presence of the surfactant, a layer of water molecules is located in the neighborhood of the BNNTs and then hydrophobic and hydrophilic segments of the surfactant reside at more distances of the BNNTs. In the absence of the surfactant, the hydrogen bond between nitrogen atom of the BNNT and hydrogen atom of water molecules is established and the distance between water molecules and the BNNTs is decreased with increase of the surfactant concentration. The obtained results for the surfactant radius of gyration and the interfacial angle between two BNNTs reveal more information about the arrangement of the surfactants around the BNNTs in the presence and in the absence of water molecules.