Fly Ash and Recycled Coarse Aggregate in Concrete: New Era for Construction Industries - A Literature Review

摘要

Use of recycled coarse aggregate inconcrete can be useful for environmental protection andeconomical terms. Recycled aggregates are thematerials for the future. Same as fly ash is also a byproductfrom various industries. Fly ash is a group ofmaterials that can vary significantly in composition. Itis residue left from burning coal, which is collected onan electrostatic precipitator or in a bag house. It mixeswith flue gases that result when powdered coal is usedto produce electric power. The advantages of using flyash far outweigh the disadvantages. The most importantbenefit is reduced permeability to water and aggressivechemicals. Properly cured concrete made with fly ashcreates a denser product because the sizes of the poresare reduced. This increases strength and reducespermeability. Globally, the concrete industry consumeslarge quantities of natural resources, which arebecoming insufficient to meet the increasing demands.At the same time, large number of old buildings andother structures have reached the end of their servicelife and are being demolished, resulting in generation ofdemolished concrete. Some of this concrete waste isused as backfill material, and much being sent tolandfills. Recycling concrete by using it as replacementto new aggregate in concrete could reduce concretewaste and conserve natural sources of aggregate. In thelast two decades, varieties of recycling methods forconstruction and demolition wastes have been exploredand are in well-developed stage. Fly ash is known to bea good pozzolanic material and has been used toincrease the ultimate compressive strength andworkability of fresh concrete.