Investigation of the Fire Resistance and Mechanical Properties of Composite Structures Strengthened with Nanomaterials

Description

Carbon nanotubes (CNTs) have been found to reduce the heat release rate of materials by forming a low permeable char that contains graphitic carbon. They also reduce the number of surface cracks in chars, which increases barrier resistance to the evolution of flammable volatiles and the ingress of oxygen during the condensed phase. This project will explore how these processes affect the fire resistance and mechanical properties of composite structures strengthened with CNTs.Composite structures reinforced with CNTs are expected to have the superior properties of CNTs. Cement is a widely used construction material in modern concrete structures. A detailed investigation of the mechanical behavior and post-fire properties of CNT-reinforced concrete structures is of paramount importance for civil infrastructure, especially in Hong Kong, which has many tall or super-tall buildings. Concrete is brittle, has much lower strength, and thus cracks easily under tension, and it is common to find serious cracks in tension areas of reinforced concrete structures. Serious spalling can also occur on the surface of concrete structures after exposure to high temperature. Since the early use of cementitious composites, continuous efforts have been made to control the size and the growth of cracks, improving the ductility of concrete structure components and preventing serious spalling. However, obstacles and problems still exist and remain unsolved. This project will examine the potential of CNT-cement matrix composite (CCMC) to resist spalling and improve fire resistance.Fiber-reinforced cement has been used in construction for centuries; considerable research has focused on reinforcing cement with steel fiber, glass fiber, carbon fiber, polypropylene fiber, and synthetic materials. In the proposed project, CNTs will be added to the cement matrix to improve its mechanical behavior and post-fire properties. Previous studies of CNT composites suggest that the addition of CNTs to concrete can refine the pore size distribution, greatly decrease the porosity, and improve the bonding strength, compressive strength, flexural strength, and failure strain; CNTs can also act as bridges across cracks and voids, thus reducing crack size and guaranteeing load transfers under tension. Ideally, CCMC would have all the superior features of CNTs. In recent years, many tragic fires have occurred in Hong Kong, and fire safety has become a major concern of the government, building designers, and the general public. Thus, given its potential to improve the fire resistance and mechanical properties of concrete, a detailed investigation of CCMC is necessary.