Smart Property And Self-sensing Ability Of Crack Of Electrical Conductive Concrete

Cumulative damage and the degradation occur when concrete structure is subjected to different loads, fatigue or erosion effect or material aging. The detection of damage is essential for the safety, serviceability and durability of concrete member. Electrical conductive concrete provide the possibility of early detection of damage progress. The investigations on the strain and damage sensing in previous studies are mainly concentrated on the damage-sensing within the elastic stage. Furthermore the studies on the smart properties and crack-sensing ability after cracking have not been reported. Based on previous studies, this work is mainly aimed at investigating the smart property and the self-sensing ability of crack of electric conductive concrete beams under flexure loading. The following aspects are carried out:(1)The influence of sole admixture with carbon fiber, disphasic conductive admixture with nano-carbon black and carbon fiber, triphsic conductive admixture with nano-carbon black, carbon fiber and steel fiber on the workability of fresh concrete are investigated. The results show that the addition of conductive admixture, especially for nano-carbon black, has negative effect on the workability of fresh concrete.(2)The influence of sole admixture with carbon fiber, disphasic conductive admixture with nano-carbon black and carbon fiber, triphsic conductive admixture with nano-carbon black, carbon fiber and steel fiber on the compressive strength and flexure strength of concrete are investigated. The results show that no significant trend of improving compressive strength was observed with the addition of nano-carbon black, carbon fiber and steel fiber. Combined use of nano-carbon black, carbon fiber and steel fiber has positive hybrid effect on the flexural strength.(3)The flexure toughness of concrete beams with steel fiber only and triphasic conductive admixture are investigated. The results show that combined use of nano-carbon black, carbon fiber and steel fiber has positive hybrid effect on the flexural toughness.(4)The smart property and crack-sensing ability of concrete beams with steel fiber only and triphasic conductive admixture are investigated, the measurement of surface resistance on the tension side was conducted using the four-probe method. The results show that the conductive concrete is suitable for the self-sensing of crack and change of load-bearing capacity. The fractional change in resistance increased with the increasing of COD (Crack Opening Deflection) and the relationship between fractional change in resistance and crack-width was strong linearly correlated. the combined use of nano-carbon black, carbon fiber and steel fiber could enhance the stability of fractional change in resistance and had positive hybrid effect on smart property of concrete.