Incorporation Of High-Volume Fly Ash To Produce Structural Lightweight Concrete
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Concrete industry is one of the main industries using large proportion and volume of our natural resources. Ordinary Portland Cement is an important source for the emission of carbon dioxide into the atmosphere because of burning fuel and raw materials’ decomposition during the production process of cement. Due to the increasing demand in concrete, one of the most effective and reliable ways to reduce the negative impact on the environment in the concrete industry is through the use of waste and by-product materials such as aggregates and ordinary portland cement replacement in concrete. The prospect of producing structural lightweight concrete using large volume of waste materials and by-products is investigated in this current study. The lightweight material used as coarse aggregate comprised of expanded shale and expanded clay. While the waste and by-product material comprised of a high volume (50% and 70%) of type C and type F fly ash, as replacement for cement by volume. The mechanical properties such as compressive strength, split-tensile strength, flexural strength, modulus of elasticity and drying shrinkage for up to 28 and 56 days are investigated as well as slump and unit weight for fresh density. The durability properties such as abrasion resistance, water absorption, resistance to chloride ion penetration and freeze and thaw resistance are also investigated. All lightweight concrete containing 50% fly ash class C and F replacement showed adequate strength in the mechanical properties. While lightweight concrete with 70% fly ash both class C and F exhibited strength lost compared to other concrete samples. Test results showed that the early ages of drying shrinkage of ordinary Portland cement and fly ash are similar but with the growth rate of drying shrinkage in OPC, it is expected for concrete incorporated with fly ash to exhibit good resistance to drying shrinkage. Test results also indicated that, concrete incorporated with fly ash showed good resistance to chloride ion penetration and there was no significant difference in abrasion for either OPC or fly ash incorporated concretes. There was significant difference in water absorption of the concrete containing fly ash. However, concretes with fly ash performed poorly and could not resist exposure to freeze and thaw mechanism especially concretes incorporated with 70% fly ash F.