Investigational study on partial replacement of metakaoline in cement concrete

The term high-strength concrete (HSC) is generally used for concrete with compressive strength higher than 41MPa. ACI Committee had defined High Strength Concrete (HSC) is the concrete that can attain specified compressive strength for design of at least 41MPa, or more. With the development of high grade cement and availability of proper mineral admixtures and chemical admixtures, it has become quite common to adopt concrete with compressive strength of 60MPa and above. Development of high strength concrete has made it possible to build taller and long span structures. But it has been proved that the comparatively higher compressive strength of High Strength Concrete is an attractive profit from engineering characteristics and economic point of view whereas, the strength behaves against the ductility of concrete by welcoming brittleness pronouncedly. To improve the ductility of High Strength Concrete, a strategy is to introduce steel in High Strength Concrete which results in development of a material with reasonable tensile strength and greater toughness which prevents the initiation and propagation of cracks. Plain concrete and High Strength Concrete possess a very low tensile strength, limited ductility and little resistance to cracking. Internal micro cracks are present in the concrete and its poor tensile strength is due to the propagation of such micro cracks. In plain concrete, structural cracks (micro-cracks) develop even before loading, due to drying shrinkage or other causes of volume change. The width of these initial cracks is few microns, but their other dimensions may be of higher magnitude. When loaded, the micro cracks propagate and open up, and additional cracks form in places of minor defects. The development of such micro cracks is the main cause of inelastic deformations in concrete. The addition of small closely spaced and uniformly dispersed fibers to concrete would act as crack arrester and would substantially improve its static and dynamic properties. This type of concrete is known as Fiber Reinforced Concrete.