Although we have been hearing recently about technologies that can produce stronger concrete, existing ordinary concrete structures can also use some help. This is where the design of the new reinforcement board combined with the new mortar lies. At present, concrete structures such as bridges and buildings are usually reinforced with carbon fiber boards on their surfaces. These panels are usually glued using organic adhesives. Unfortunately, these adhesives do not withstand burning and may fail when exposed to moisture.
On October 26, the Korea Institute of Civil Engineering and Construction Technology (KICT) announced an effective method of structural reinforcement: using a mixture of non-combustible carbon fiber fabric grid and cement mortar, which can double the load-bearing capacity of concrete structures, and they The usable life of the product is tripled.
Initially, more than 90% of South Korea’s infrastructure (such as bridges and tunnels) and residential buildings were constructed with concrete. For concrete structures, organic binders are generally used to apply carbon fiber sheets to the surface of the concrete structure. However, organic adhesives are flammable and cannot be applied to structures with wet surfaces. If these carbon fiber boards are exposed to moisture, they may fall off the structure and fall off.
The KICT research team led by Dr. Hyeong-Yeol Kim has developed an efficient reinforcement method to deal with degraded concrete structures. In this method, a thin prefabricated textile reinforced mortar (TRM) panel is used, which is made of a carbon textile grid and a thin layer of cement mortar. In addition, the TRM reinforcement method can adopt the form of cast-in-place construction. Using KICT's method, a 20mm thick TRM panel is attached to the surface of the existing structure, and then the space between the existing structure and the panel is filled with grout. The grout is used as an adhesive.
Both carbon fiber fabric and cement mortar are non-flammable materials with high fire resistance, which means they can be effectively used to reinforce concrete buildings that may be exposed to hazards. This construction method can also be applied to wet surfaces even in winter, and the panel will not fall off in the case of water ingress. In addition, unlike steel bars, carbon fiber does not corrode, so it can be effectively used to reinforce highway facilities and parking buildings that often use deicing agents, and to reinforce offshore concrete structures exposed to chloride.
Failure tests conducted in KICT show that the failure load of concrete structures reinforced with TRC panels is at least 1.5 times greater than that of unreinforced structures. In addition, the chloride resistance of TRM panels has been evaluated to evaluate its service life in a chloride-rich environment. The durability test and analysis of the TRM panel show that the service life of the panel exceeds 100 years. This increase can be attributed to the cement mortar developed by KICT, which contains 50% granular blast furnace slag, which is an industrial by-product produced by ironworks. It has higher fire resistance than conventional cement mortar, and its cost is half of traditional mortar in terms of economic efficiency.
The newly developed reinforcement method uses very thin TRM panels, which are versatile and can be used as building exteriors, repair and reinforcement materials, and other applications. In the future, if panels can be made of insulating materials, they are expected to replace fire-prone building insulating materials, reducing the need for internal insulation.
Dr. Jin said: “In order to facilitate production and transportation, the manufacturing size of TRM panels is relatively small, 1m x 2m, and must be connected at the construction site. An effective method for connecting panels is currently being developed, and the performance test of this method will To be carried out at the end of 2020."
Recently, a paper published in the "Materials" magazine described this research.