低掺量石墨水泥基材料的压敏特性

Piezoresistivity of cement based material with small amount of graphite

通过减水剂将少量石墨加入水泥基材料中制成石墨水泥基材料试样,采用交流分压电路测量其电阻率,研究其在一次性加载破坏试验中的压敏特性.试验结果表明,低掺量石墨粉作为导电组份加入水泥基材料后会导致其强度降低,但可以使水泥基材料具有一定程度的压敏特性.随着石墨掺量的增加,各组试样电阻率的离散性变小,材料的压敏特性提高,在加载过程电阻率的波动变小.在本试验的测量方法下得到的石墨水泥基材料的压敏特性曲线与混凝土材料的应力应变曲线有相关性,试样的电阻率随着应力的增大而产生变化的过程大体可分为3个阶段,即波动阶段、稳定下降阶段和急剧下降阶段,分别对应混凝土材料应力应变关系的弹性变化、非弹性变化和应变迅速增大阶段.

Graphite-cement specimens were made by adding water reducing agent in cement,and the specimens＇ piezoresistivity in a destructive overload experiment was mensurated by a series connected AC circuit.The results present that,if a small amount of graphite was mixed in,the cement material＇s uniaxial compressive strength will decrease,at the same time the material＇s piezoresistence coefficient will ascend.As the amount of graphite was increased within a small range,the deviation of specimens＇ relative resistivity decreases,and the piezoresistivity of the material increases.Furthermore,the resistivity of the specimens becomes stable while being loaded.By examining the piezoresistivity curves of the graphite-cement material,similar shape with the stress-strain curves can be got in these experiments.There are three stages while the material＇s relative resistivity is changing along with the increase of stress imposed on it which are undulate stage,slowly descend stage and rapidly descend stage.These stages are accordant to the three stages of the failure of cement based material,which are elastic stage,elastic-plastic stage and failure stage.