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In this paper, functionalized nanotube-reinforced cementitious composites were prepared, and the mechanical property test results showed that the 28d flexural strength of the composite was increased by 41.58% at a hydroxylated carbon nanotube mass fraction of 0.08wt.% compared to the original cement mortar. Carboxylated carbon nanotubes with a mass fraction of 0.02%, on the other hand, increased the 28d compressive strength by 99.12%. Probing the effect of the presence of functional groups on carbon nanotubes on the CNT/C–S–H interface by first principles. The results showed that the shear strengths (11.392MPa and 14.130MPa) of hydroxylated carbon nanotubes and plain carbon nanotubes at the interface with cementitious (CNT-OH/CSH and CNT/CSH) were lower than the shear strengths (21.584MPa) of carboxylated carbon nanotubes at the interface with cementitious (CNT-COOH/CSH). The adsorption of functional groups on carbon nanotubes changes the electron distribution on the surface of carbon nanotubes. The introduction of carboxyl groups exacerbates the charge transfer between carbon nanotubes and cementitious groups and promotes the generation of solid chemical bonds. This is the reason that carboxylated nanotubes added as reinforcement to cement mortar give better strength to the composite than hydroxylated nanotubes.

At high strain rates, the dynamic response of cement mortar, a heterogeneous material with damage, was experimentally studied under three different stress states: (1) one-dimensional stress state by using the SHPB technique, (2) one-dimensional strain state at high pressures from 1 to 5 GPa by using a one-stage gas gun, and (3) quasi one-dimensional strain state by using an improved passive confining SHPB technique. The experimental results indicate that cement mortar is a kind of nonlinear rate-dependent material with internal damage evolution, and that the confining pressure greatly influences its ductility and strength. The main results are given and discussed.

In this paper, an ultrasonic wave experiment is carried out for detecting viscosity property of cement mortar. The specimen of cement mortar of length 0.5m and radius 0.045m is formed. In order to detect the property of ultrasonic wave propagation at different position, the large specimen is cut into short specimens. Then, ultrasonic wave experiments for the specimen with different length are performed. The experimental results show that the clear attenuation of the amplitude of ultrasonic wave, and this implies the cement mortar is a material that possesses viscous properties. A viscoelastic model is proposed and related parameters in the model are numerically determined with the ultrasonic wave experimental results. This is an effective method to measure parameters of the constitutive relation of cement mortar by ultrasonic wave technique.

The impact behavior of cement mortar, a heterogeneous material with damage, were experimentally studied under three different stress states: (1) one-dimensional-stress state by using the SHPB technique, (2) one-dimensional strain state at high pressures from 1 to 5 GPa by using an one stage gas gun and (3) quasi one-dimensional strain state by using an improved passive confining SHPB technique. The experimental results show that cement mortar is a kind of nonlinear rate-dependent material with internal damage evolution, and the confining pressure greatly influence its ductility and strength. The main results are given and discussed.