Abstract
Polyurethane cement (PUC) is a kind of high-strength composite bending and strengthening material that is made by adding an appropriate amount of super fine aggregate, such as cement, into the polyurethane matrix. Carbon nanofiber polyurethane cement (CNFPUC) prepared by adding an appropriate amount of carbon nanofiber (CNF) can significantly reduce the resistivity of PUC. In order to reveal the change regulation of electrical resistivity of CNFPUC under fatigue load, the four-point bending fatigue life test of CNFPUC under different temperatures and stress levels was conducted by using a multifunction test device on a mixture of UTM-30 asphalt. The results showed that the resistivity increased slightly with the increase of bending strain in the process of the CNFPUC bending test, which presented a two-stage trend of a small increase and a sharp increase, and the maximum bending tensile stress was up to 26.65 MPa. Under periodic load, the resistivity increased with the increase of stress level and cycle times. When the damage amount reached 90%, the fatigue resistivity increased sharply, and with the increase of stress level, the effect of temperature on resistivity decreased gradually. This study may provide a theoretical basis for practical engineering applications.
Highlights
As a new reinforcing material being used in recent years, polyurethane cement (PUC) is a kind of high-strength composite made by adding an appropriate amount of superfine aggregate, such as cement, into a polyurethane matrix
The cohesional strength between Carbon nanofiber polyurethane cement (CNFPUC) and concrete was greater than 3.47 modulus specimen under failure (MPa)
The failure interface did not occur on the interface between the concrete and the CNFPUC material, which indicated that the CNFPUC material had good bonding performance with the concrete
Summary
As a new reinforcing material being used in recent years, polyurethane cement (PUC) is a kind of high-strength composite made by adding an appropriate amount of superfine aggregate, such as cement, into a polyurethane matrix. By pouring PUC material at about the thickness of 25 mm onto the bottom of a concrete beam or onto the side of a concrete column, the concrete beam and the column will be subjected to force in coordination with the concrete beam and the column. This reinforcement method is between the external reinforcement method and the increasing section method, but the increased area of the cross-section is small, which has little effect on the structural appearance and the bridge clearance; this has a good reinforcement effect [1,2,3,4]. With the gradual improvement of the reliability requirements of the structure, it is urgent that methods to monitor and evaluate the safety conditions of the strengthened bridges be
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