Mustafa Şahmaran

Effect of Fly Ash and PVA Fiber on Microstructural Damage and Residual Properties of Engineered Cementitious Composites Exposed to High Temperatures

This paper discusses the influence of high volumes of fly ash and micro polyvinyl alcohol (PVA) fibers on the fire resistance and microstructure of engineered cementitious composites (ECC). Composites containing two different contents of fly ash as a replacement for cement (55 and 70% by weight of total cementitious materials) are examined. To determine the effects of microfibers and ultrahigh ductility of ECC, ECC matrix mixtures of similar composition except PVA fiber are also produced and tested for the fire resistance. The mixtures are exposed to temperatures up to 800°C for one hour. Fire resistances of the mixtures are then quantified in terms of the residual mechanical properties (strength, stress-strain curve, deflection, and stiffness) and mass loss. The role of PVA fibers and fly ash is discussed through the analysis of microstructure and fiber-matrix interactions as a function of heat treatment. The microstructural characterization is examined before and after exposure to fire deterioration by ...

Engineered Cementitious Composites: Can Composites Be Accepted as Crack-Free Concrete?

Because conventional concrete is brittle and tends to crack easily under mechanical and environmental loads, there are concerns with durability. During the past decade, the effort to modify the brittle nature of ordinary concrete has resulted in high-performance fiber-reinforced cementitious composites (HPFRCCs), which are characterized by tensile strain-hardening after first cracking. Engineered cementitious composites (ECCs), a special type of HPFRCC, represent a new concrete material that offers significant potential to reduce the durability problem of concrete structures. Unlike ordinary concrete and fiber-reinforced concrete materials, ECC strain-hardens after first cracking, as do ductile metals, and it demonstrates a strain capacity 300 to 500 times greater than normal concrete. Even at large imposed deformation, crack widths of ECC remain small, less than 80 μm. Apart from unique tensile properties, the relationship between crack characteristics and durability—including transport properties (permeability, absorption, and diffusion); frost resistance with and without deicing salts; performance in a hot and humid environment; performance in a high-alkaline environment, corrosion, and spall resistance; and self-healing of microcracks—is presented. Research results indicate that, because of intrinsic self-control tight crack width, robust self-healing performance, and high tensile strain capacity, many durability challenges confronting concrete can be overcome by using ECCs.

Engineered cementitious composites: An innovative concrete for durable structure

This paper reviews recent research on the durability properties of Engineered Cementitious Composites (ECC), a special type of high-performance fiber reinforced cementitious composites designed with micromechanical principles, under various environmental and mechanical loads. The durability subjects include (a) ECC cracking and transport properties (permeability, absorption and diffusion), (b) corrosion resistance (c) freeze–thaw and salt scaling resistance, (d) performance under hot and humid environment, and (e) performance under high alkaline environment. The research results indicate that due to intrinsic self-control tight crack width and high tensile strain capacity, many durability challenges confronting concrete can be overcome by using ECC. The enhanced performances of ECC under mechanical and environmental loads are expected to contribute substantially to improving civil infrastructure sustainability by reducing the amount of repair and maintenance during the service life of the structure.