Piezoresistivity Of Cementitious Composite Containing Graphite Nanoplatelets

Cement-based smart composite materials will provide important supports for the intellectualization of concrete structure. Graphene and composite materials are a research hotspot in recent years, but the application research of graphene in cement-based smart composite materials is still very rare. The ductility of present cement-based smart composite materials is not good, then the self-sensing range of tensile strain is far less than the compressive strain sensing range. Therefore, in this paper, the latest carbon based nano materials –Graphene Nanoplatelets(GnPs) is introduced into cement motar and high strain hardening cementitious composites(SHCC) with high ductility. Comparing the differences of sensitivity with the two kinds of composite materials, it has turned into a key to explore a new type of smart cement based materials for structure health monitoringIn this paper, the main research contents are as follows:1.In order to achieve a better dispersion effect, making the GnPs more evenly distributed in the cement matrix, using the methods of different dispersant and ultrasonic dispersion techniques to study the dispersion effect of GnPs. Developing the preparation method of GnPs- cement mortar. The results showed that the dispersion effect of GnPs will affect its reinforcing capability to a large extent.2.The compressive strength of GnPs-mortar decreased with the increasing GnPs content, but the introducing of type M5 GnPs makes the compressive strength of GnPs-mortar is higher than the cement mortar, presenting an enhancement effect. To improve conductivity of composite materials, type M5 is better than type M25 of GnPs. The percolation threshold of GnPs is about 1%. The pressure sensitivity of GnPs-mortar first increased and then decreased with the increasing dosage of GnPs and the gage factor is under 22.3. GnPs-SHCC had higher tensile strength and compressive strength, the incorporation of GnPs increased the ultimate tensile strength and ultimate tensile strain of SHCC. The resistance change rate of GnPs-SHCC had high sensitivity of tensile strain, the damage of SHCC could perceive through the change of the resistance change rate curve during cyclic tensile stress.The gage factor of GnPs-SHCC is much higher than the same GnPs content mortar.With the increasing of GnPs dosage, the repeatability of resistivity curve was improved, so the GnPs-SHCC had better piezoresistivity than GnPs-motar.4.The resistance of GnPs-SHCC decreases with the increasing strain during the whole compressive process, which showed that GnPs-SHCC had a wide range of strain sensing range about 2.5%. But the gage factor of GnPs-SHCC decreases with the increasing strain.