Abstract
To examine the intelligent sensing properties of polyurethane cement mixed with carbon nanofiber and used as beam reinforcement material, 7 reinforced concrete T-beams were made and reinforced with carbon nanofiber polyurethane cement material (CPUC). Four-point bending tests were conducted. Reinforcing concrete beams with CPUC material might increase the yield load and ultimate load of beams significantly. The overall stiffness of the reinforced beam was enhanced. CPUC played a significant inhibitory role in the formation and development of beam cracks. A sudden change in the rate of CPUC resistance can be used to monitor the yield of a steel bar, and then, a safety warning for the components can be launched. By establishing a model of the relationship between the resistance change rate and the external load, the bearing capacity of the beam is evaluated in real time, and the dual effects of reinforcement and health monitoring of the beam are realized simultaneously.
Highlights
Polyurethane matrix composite reinforcement material is a new reinforcement material that was developed in recent years; it is a type of highstrength reinforcement material made of polyurethane matrix, which is used as cementitious material by adding appropriate amounts of ultrafine aggregate into the matrix
The ultimate load is higher than the yield load. e load-deflection curve can be divided into four stages
The seven reinforced concrete T-beams were made out, and six bottoms of them were reinforced by carbon nanofiber polyurethane cement material (CPUC) material. e four-point bending test was carried out to obtain the following conclusions: (1) Reinforcing concrete beams with CPUC material could increase the yield load and ultimate load of beams significantly. e overall stiffness of the reinforced beam was enhanced
Summary
Polyurethane matrix (polyurethane matrix, PUM) composite reinforcement material is a new reinforcement material that was developed in recent years; it is a type of highstrength reinforcement material made of polyurethane matrix, which is used as cementitious material by adding appropriate amounts of ultrafine aggregate (such as cement, silica fume) into the matrix.PUM is used by pouring approximately 25 mm thick PUM material on the sides of concrete beams or columns for reinforcement. e essence of the reinforcement method is between the external reinforcement method and the increasing section method, but the area of increased section is small and has little influence on the structure’s appearance or bridge clearance, and it has a good reinforcement effect (see Figure 1). PUM is used by pouring approximately 25 mm thick PUM material on the sides of concrete beams or columns for reinforcement. Compared with the traditional reinforcement methods for beams and columns, PUM material has the advantages of making a strong bond with concrete and having good fluidity, environmental friendliness, light weight, high toughness, and easy construction. It has been gradually applied to reinforcement and reconstruction projects of concrete bridges and piers [1,2,3,4]. PUM material is limited only to actively increasing the strength and stiffness of the bridge and pier columns and does not have an intelligent effect after reinforcement. Erefore, it is difficult to make timely and quantitative evaluations of the condition of the columns during their service period, which increases the cost of monitoring and testing after the reinforcement of the bridge. As people prioritize structural safety and comfort, intelligent materials have attracted increasing attention in the field of civil engineering, and the detection and monitoring of structural health and safety have become an important part of civil engineering, disaster prevention and mitigation [5,6,7,8]
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