Cong Lu

Mechanism of cement paste reinforced by graphene oxide/carbon nanotubes composites with enhanced mechanical properties

This study presents the enhanced mechanical properties of cement paste reinforced by graphene oxide (GO)/carbon nanotubes (CNTs) composites. The UV-vis spectroscopy and optical microscopy results show that the dispersion of CNTs in the GO solution is much better than in an aqueous solution due to the higher electrostatic repulsion, which allows a completely new approach of dispersing CNTs rather than by incorporating a dispersant. More importantly, the GO/CNTs composite plays an important role in improving the compressive and flexural strength of cement paste by 21.13% and 24.21%, which is much higher than cement paste reinforced by CNTs (6.40% and 10.14%) or GO (11.05% and 16.20%). The improved mechanical properties of cement paste are attributed to better dispersed CNTs and enhanced interactions among CNTs by the GO incorporation. Finally, the space interlocking mechanism of the GO/CNTs/cement paste composite with enhanced mechanical properties is proposed.

The Effect of Fiber Orientation on the Mechanical Properties of SHCC

Strain-Hardening Cementitious Composites (SHCC) are materials featuring strain-hardening behavior accompanied by formation of multiple cracks. The distribution of fiber orientation in SHCC members is affected by member thickness due to the limited freedom of rotation for fibers near the surfaces. This paper first demonstrates how to acquire fiber orientation distributions for various member thicknesses from geometrical consideration. The distribution of fiber orientation is found to be between ideal 2D distribution and 3D distribution, so the tensile performance should be in between as well. Constitutive law for a single crack is computed based on obtained distributions. Stress-strain curves for tensile members are also simulated. This study reveals the theoretical effect of member thickness on SHCC behavior. Compared to laboratory data obtained from small-size specimens, a thickness-dependent reduction factor for mechanical properties (mainly tensile strength and ductility) should be considered in the design of real structural members.