Molecular dynamics investigation on the crack-bridging role of coated graphene oxide on steel fiber reinforced concrete

Graphene oxide (GO) coated steel fiber-reinforced concrete has been proposed in the literature and fabricated by an innovative three-step dip coating method. The experimental results revealed that the coated-GO nanosheets could significantly enhance the unevenness and water affinity of the fiber's exterior, thus enhancing the frictional force and chemical reactivity of steel fibers in the cement matrix. Furthermore, the coated GO nanosheets can act in a “crack-bridging role” by cooperating with the generated hydration products to reinforce the load-supporting ability of fiber-reinforced concrete. However, the reinforcing mechanisms of the crack-bridging role of coated-GO on steel fiber-reinforced concrete have not been fully understood. Hence, in the current investigation, the molecular dynamical (MD) simulation was applied to reveal the reinforcing mechanisms of coated-GO on the fiber-reinforced concrete. The simulation results indicate that the caking capacity at the interface of the steel fiber and the cementitious stroma can be effectively improved by coated GO, remarkably improving the tensile stress of the connection area by 158.4–496.7 %. After the GO coating treatment, the failure of the fiber exterior and concrete stroma bonding area is more inclined to stretchability destruction. The microstructure evolution characteristics and strain law prove that the strain and bonding capacity of structural failure areas between fiber exterior and concrete stroma can be remarkably enhanced due to the crack-bridging role of the coated-GO nanosheets. Finally, the energy change characteristics calculation results verify that the coated-GO nanosheets greatly enhance the bonding energy by 400–6200 % between the molecules of the bonding region, thus strengthening resistance to load. The results of this research will both strengthen the mechanism of GO in cement-based composites and guide the efficient use of GO in cement engineering in the future.