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The IUP Journal of Structural Engineering :
An Analysis of Hydrated Lime Included Fly Ash Concrete Based on SEM
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With fly ash concrete gaining popularity, owing to both environmental and economic factors, it is critical that we tackle its practical shortcomings, most prominent of which is its low early strength development. Inefficient pozzolanic reaction of fly ash particles has been long deemed as its cause. A prevalent theory suggests that this lack may be overcome by addition of hydrated lime (calcium hydroxide), and thus promoting increased pozzolanic reaction, resulting in an overall enhanced matrix within the concrete structure. This paper is a study of fly ash concrete supplemented with hydrated lime and its subsequent effects on various mechanical properties, so as to form a collection of basic data, which is then compared to those values corresponding to conventional fly ash concrete. The study makes informed conclusions based on the results obtained by theorizing micro mechanics of the mix, expected chemical reaction of constituents and from SEM analysis.

 
 

In the light of the recent emphasis on environmental and economic wellbeing concerning the adverse impacts of construction materials, fly ash concrete is fast becoming a topic of vital importance. Fly ash, a pozzolanic byproduct from thermal power plants, is increasingly being incorporated into concrete to create cheaper, eco-friendly, yet strong and durable fly ash concrete with up to 30% replacement for OPC. But attainment of strength via pozzolanic action of fly ash particles is slow and results in low early strength of fly ash concrete and adversely affects its popularity in the field.

Hydrated lime (calcium hydroxide), the combination of lime (calcium oxide) and water, is popular in construction activities, most commonly for plastering purposes. A prevalent theory suggests that effective pozzolanic reaction of fly ash particles is hindered due to unsatisfactory quantities of lime in most fly ash compositions (Barbhuiya et al., 2009) and this is the cause of low early strength in fly ash concrete. This lack may be overcome by addition of hydrated lime to the mix and thus, in turn, improving the overall performance of fly ash concrete.

 
 

Structural Engineering Journal, Fly ash concrete, Hydrated lime, Mechanical properties, Microstructure, Pozzolanic, SEM