ELECTRIC RESISTANCE MEASUREMENT OF CARBON FIBRE SMART CONCRETE

After having measured the electric resistance of carbon firbre reinforced concrete (CFRC) by applying a D. C. current, it was found that the current passing through the specimen under a constant voltage decreased with the time, and if changing the value of voltage, the electric resistance was obviously affected. When current flew through the specimen, polarisation emerged under a high votage (>5 upsilon), but that could be neglected under a low voltage (<5 upsilon).(1)

Effect of HPMC on the Piezoresistivity of Smart Concrete Aggregate with Z Shape

Cement mortar with carbon fiber(CFc)and resin-cement mortar with carbon fiber(CFrc)were used as inner and outer cores of smart aggregate with Z shape,respectively,which was used as the basic perception units to prepare smart concrete aggregate with a mosaic structure(SAMS).The hydroxpropyl methylcellulose(HPMC)was taken into consideration to improve the properties of mortar;by using HPMC,the structure of SAMS was optimized and its mechanical and electrical properties were evaluated.The experimental results show that the toughness of mortar could be improved by the complex that formed by epoxy resin,and the effect of HPMC on the flexibility of CFc was greater than that on the flexibility of CFrc;the feasible designing indicates that the CFc-Z core and CFrc-Z core could be used as inner and outer cores of SAMS.When the proposed dosages of HPMC in inner and outer cores are 0.35wt%and 0.2wt%,respectively,it could give an effective prediction for the damage of concrete during the loading process.

Characteristics of Smart Concrete with Fiber Optical Bragg Grating Sensor

Based on the advantages of the fiber Bragg grating sensing technology,this paper presents a principle of a novel smart concrete with fiber optical Bragg grating sensor,analyses the theory and characteristics,illustrates the key technology and method to make the fiber Bragg grating sensor for the smart concrete,and proves the feasibility with experiments.The results indicate that the smart concrete with fiber Bragg grating sensors is feasible in the structure monitoring and damage diagnosing in the long run.

Effect of CF and RPP on the Mechanical and Electrical Properties of Smart Aggregate

By using redispersible polymer powder（RPP） and carbon fiber（CF） to adjust the flexibility and electrical properties of the smart aggregate, a new kind of smart aggregate with Z type structure was proposed. The study shows that Z type aggregate is more sensitive to the feedback of external force than the prism aggregate in the same loading environment, and it indicates that Z type aggregate is more suitable for the research and application of concrete health monitoring. Although the incorporation of RPP would cause the compressive strength of the aggregates and the elastic modulus of hardened cement mortar to reduce slightly within the dosage of RPP by 2.25% because of the polymer film formed in the internal system, this would improve the deformability of the aggregates. In the early loading stage（in the first 60 seconds）, the intelligent concrete specimens implanted with Z type smart aggregate do not show higher sensitivity as expected, although the resistance change rate changes a little bit more, the overall of it is still in balance. Adding RPP could improve the flexibility of smart aggregates exactly, and it plays an active role in prolonging the life of the smart aggregates. By implanting Z type aggregates the damage and failure of the concrete structure could be predicted accurately in this study. The results of this paper will help to promote further research and application of intelligent concrete.

Resistance Responses of Carbon Fiber Cement to Cycled Compressive Stresses

The stress-resistance relationship of carbon fiber cement was studied.Attention has been paid to explore the improvement of the stress-resistance sensitivity under cycled stress restriction.The prismy carbon fiber cement sensors were pre-fabricated.The factors such as contents of carbon fibers.silica fume,dispersant and the w/c were taken into account.The electrical resistance variations with the dynamic and static loads were simulated using a strain-controlled test machine.The test results show that there is an optimal fiber content,with which the compression-sensitivity achieves a high level.The addition of silica fume can improve the sensitivity.Under the optimal test conditions,the measured resistances can greatly correspond with the changes of the load.

Mechano-electric Effect of Hardened Cement Paste During Quasi-static Loading

Mechano-electric effect of cement paste was investigated in this paper. As compressive stress was applied on the specimen, an electrical current was observed. The intensity of the electrical current increased with stress increasing, and decreased with stress decreasing. Different measurement methods were also discussed in this paper. This phenomenon was related to the electrokinetic phenomenon of solid/liquid interface in cement paste. The study on mechano-electric effect of hardened cement paste provides a new method for making smart concrete structures.