This paper reports the result of an investigation on the effect of initial stress on wave propagation in multi-walled carbon nanotubes (MWNTs). The initial stress in MWNTs often occurs due to thermal or lattice mismatch between different materials. Using a laminated beam model and considering the interaction of van der Waals forces between two adjacent nanotubes, the effects of initial stress in MWNTs on the number of wave speeds and the vibration amplitude ratio between the two adjacent tubes are described. It is noticed that the number of terahertz waves in MWNTs with initial stress not only depends on the response frequency and the noncoaxial vibrational modes, but also depends on the initial stress in the MWNTs.

High fluidity concrete exhibits an excellent self-compacting property. However, the application of typical high-fluidity concrete is limited in the normal strength range (18~35 MPa) due to the large amount of binder. Therefore, it is important to solve these problems by adding a viscosity modifying agent (VMA) with a superplasticizer (PCE), which helps to improve the fluidity of the concrete. In addition, the rheology and stability of the concrete with VMA can be improved by preventing bleeding and segregation issues. Current studies focused on the physical phenomena of concrete such as the fluidity, rheological properties, and compressive strength of normal-strength, high-fluidity concrete (NSHFC) with different types of a polycarboxylate-based superplasticizer (NPCE). The obtained results suggested that the combinations of all-in-one polycarboxylate-based superplasticizers (NPCE) did not cause any cohesion or sedimentation even stored for a long time. The combination of three types of VMA showed the best fluidity (initial slump flow of 595~630 mm) without any segregation and bleeding, and the compressive strength at 28 days was also found to be the highest: 34–37 MPa. From these results, the combination of PCE (2.0%) + HPMC (0.3%) + WG (0.1%) + ST (0.1%) showed an 18% higher plastic viscosity and -4.4% lower yield stress than Plain.

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