The Microstructure Of Carbon Fiber Reinforced Cemen And Its Influence On The Stress-resistance Sensitivity

In this dissertation, the overseas and domestic investigations relative to the stress-resistance sensitivity of carbon fiber reinforced cement (CFRC) was comprehensively reviewed and analyzed. On the basis of predecessors' researches, the influence of surface treatment of carbon fiber, the contribution of material components and the microstructure of cement paste on the stress-resistance sensitivity of modified cement paste were systematically presented in progress. The application feasibility of the stress-resistance sensitivity of CFRC on engineering structure was explored as well. According to the above research results, the following conclusions can be obtained:(1) Surface treatment of carbon fiber was available to improve the hydrophilic characteristic of carbon fiber markedly as well as the bond strength between carbon fibers and cement paste increased. At the same time, as for the response of stress-resistance sensitivity of carbon fiber cement composites to load, it was found that the sensitivity of CFRC to the compressive stress and tensile stress, and the anti-fatigue of CFRC increased. Consequently, the reversibility of the change in resistance of CFRC was improved during repeating load when the surface of carbon fiber was treated.(2) It was shown that the CFRC with w/c=0.35, carbon fibers 0.3% and the dispersant 0.4wt% was the optimal mixture because it can present the most sensitive and well-regulated smart performance for the response of load. During tensile loading for the used samples, the measured resistance of CFRC specimens as the response of the tensile stress increased regularly. During compressive loading, the expected resistance values decreased and the change of resistance with stress-strain was sensitive and stable. As a result, the excellent CFRC with the optimal mixture can sense the character and the change of loading.(3) The influence of contents of gel and crystal mineral phase of cement paste on the stress-resistance sensitivity was also investigated in my thesis. The pores with the 10~100nm range were of particular significance for stress-resistance sensitivity. It implied that the response characteristics of stress-resistance sensitivity for the CFRC can be controlled by adjusting the pore size distributions. The relationship between the vaporing water and the compression sensitivity was studied by the relative experimental. The results showed that the content of vaporing water into CFRC specimens can change the sensitivity of CFRC to the loading. Physical model was proposed to explain the effect of mineral phase composition and moisture content on stress-resistance sensitivity mechanisms.According to the above research results, application of CFRC on engineering is explored basically. It is hard for CFRC to directly sense the load of vehicles,and the special component which can enhance the stress by changing the pressed area. The load of heavy and mid-weight vehicles can be monitored by the stress-resistance response of CFRC samples which were been setting on the highway concrete pavement. As a result, the vehicle weight can be calculated as the function of pressure and resistance change.