Mechanical Behavior of Fly Ash Concrete A Critical Review

Abstract

Concrete structure is the most common all over the world. Cement is the major ingredient of concrete. Though the raw materials needed for manufacture of cement are available in most parts of the world, many countries have severe shortage of cement, although their needs are vast. The search for suitable substitute for cement, either partially or fully, has thus become a challenge for planning the development of many of the third world countries. At the same time, large-scale industrialization has led to newer environment problems related to disposal of industrial byproducts like fly ash. The thermal power stations existing in the world produce million tons of fly ash worldwide every year. There are large numbers of other industries, which also use coal for firing their boilers, producing large amounts of fly ash, which are generally collected by mechanical collectors. A large amount of land is being wasted for disposal of fly ash, which can otherwise be used for housing, agricultural, industrial or some other essential purposes. Moreover, during production of cement, a huge amount of CO₂ is added to green-house gasses by burning coals which causes environmental pollution. It is well known that fly Ash is low cost material and use of fly ash in concrete reduces the amount of cement required. Thus use of fly ash in concrete minimizes the construction cost and improves the environment quality by reducing the emission of harmful gas like CO₂ into air that caused during manufacturing of cement. In addition to economic and environmental benefits, the use of fly ash improves various mechanical properties of concrete. It is observed from the previous researches that fly ash collected from electrostatic precipitator of thermal power plants is very much suitable for use in production of high performance concrete. This review paper focuses on the various mechanical properties of fly ashconcrete.

Keywords: compressive strength, durability, fly ash, w/c ratio, hydration, chloride concentration, sulfate ion concentration