Abstract: Studies show that adding carbon fiber to concrete to form a conductive network can make concrete feel its own stress, strain, cracks, and damage according to the change of conductive network, and improve the strength and durability of concrete. In view of the self-sensing characteristics of carbon fiber, carbon fiber reinforced cement-based composites are put forward as a new intelligent sensing material. Through unconfined compressive strength test, resistivity test, microscopic test, and model test, the influence of fiber volume fraction and fiber length on unconfined compressive strength and resistivity change rate of carbon fiber reinforced cement-based composites are studied. A carbon fiber reinforced cement-based composites "sensor" is made according to the optimal ratio, which is implanted into cement-based composites components to establish the functional relationship between the sensor resistivity change rate and the stress of cement-based composites components, so as to realize the stress monitoring of cement-based composites components by the sensor. The results show that, in the study of the strength of carbon fiber reinforced cement-based composites, the unconfined compressive strength of carbon fiber reinforced cement-based composites is affected by both carbon fiber volume fraction and carbon fiber length, and the compressive strength increases first and then decreases with the increase of both. In the test range, 2% is the optimal volume fraction and 6 mm is the optimal fiber length. In the study of the resistivity change rate of carbon fiber reinforced cement-based composites, when the carbon fiber volume fraction is 1% and the fiber length is 3 mm, the resistivity change rate of the specimen is the largest, and the self-sensing sensitivity of carbon fiber reinforced cement-based composites is the best. There is an obvious exponential relationship between the resistivity change rate of the sensor embedded in the component and the stress of the cement-based composites component. Through establishing a stress prediction formula based on resistivity change rate, the stress state monitoring of the cement-based composites structure can be realized.

Key words: carbon fiber, cement soil, unconfined compressive strength, resistivity change rate, self-sensing, sensor