Study On Graphene Nanoplatelets Cement Mortar Composite

The Graphene nanopalates(xGnP)has good conductivity along its plane direction,and provide cement-based materials voltage-dependent characteristic,self-sensing to stress and damage.Further more,xGnP can improve the compressive and flexural strength of the cement-based meterials.The article made a deep research to the influence about xGnP to cement-based materials.According to previous research,the dispersant could improve the dispersion of xGnP in water.The tests selected four types of water:deionized water,tap-water,saline solution and alkaline solution;two types of dispersant:PVP for nonionic type,and SDBS for anionic surfactant.The result showed that,the dispersion effect of SDBS was better than PVP in deionized water,but in the other three types of water,PVP was better than SDBS.Three main types of dispersant were adopted,which were water ultrasound,ultrasound probes,high-speed shearing.The result showed that,the effect of ultrasound probes was much better than water ultrasound,and the effect of high-speed shearing was getting better as the increase of rotate speed.The former dispersion effect was as good as ultrasound probes when the rotate speed reached 8000r/min.Two methods were confirmed finally.(1)15min high-speed shearing and 15min ultrasound probes.(2)30min ultrasound probes.Physical property test includes setting time,mortar fluidity and mechanical strength.Results showed that there's a retarding effect for setting time.The retarding effect got worse as the xGnP increased.Water requirement of normal consistency increased too.Fixed water method and invariant water method for initial and final setting time both showed an increasing tendency,except for initial setting time under fixed water method.Mortar fluidity decreased with the increase of xGnP,the dampening effect is xGnP-C-500<xGnP-M-15<xGnP-M-25.Flexural strength increased under any curing time while compressive strength first decreased at 7d,then increased at 28d.the final strength of xGnP-C-500 and xGnP-M-15 improved while xGnP-M-25 stayed the same.Piezoresistivity of xGnP-M-15 at 1%by weight of cement is the best.Piezoresistivity increased with the compressive stress with a decreasing speed.And it will increase under damage.Piezoresistivity showed a sharp increase under above 28MPa.The pattern is very similar to stress-strain curve of cement materials.