Advantages And Disadvantages Of Fly Ash

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Fly Ash Fly ash is a by-product of coal from power stations. It helps to improve the durability of concrete. Through the observation under the SEM test, It can be noticed that the fly ash sample consists of almost regular spherical or cenospheres particles ranging 2 um to 14 um in diameter (Ismail et al., 2007). This is due to the fact that fly ash is produced by fusing small and light particles that remain suspended in the burning chamber but are captured afterwards by electrostatic filtration equipement (Rivera et al., 2013). The huge particle size of fly ash enables it to be ball mill again in order to reach a smaller particle size. Based on past research, the binding of OPC with fly ash increases the compressive strength due to the denser …show more content…

From a research carried out by Ahmaruzzaman (2010), bituminous coal fly ash consists of principal components namely silica, alumina, iron oxide and calcium with various amount of carbon as measured by the loss of ignition (LOI) whereas, lignite and sub-bituminous have higher concentrations of calcium and magnesium oxide with reduced percentages of silica and iron oxide as well as low carbon content. Class F fly ash is pozzolonic in nature because it contains 20% lime (CaO) and they requires a cementing agent which is OPC, quicklime or hydrated lime with the presence of water in order to react and produced cementitious compounds (Zode, n.d.). Since bituminous fly ash has lower amount of calcium than sub-bituminous, it is a class F fly ash. Class C fly ash usually has cementitious properties as well as pozzolanic properties due to free lime, but Class F is rarely cementitious when mixed with water alone (Ismail et.al., 2007). Therefore, sub-bituminous and lignite is a type of fly ash that is class C.

Besides reducing the usage of cement in concrete, there are several other advantages of using fly ash as supplementary cementitious materials. First of all, it acts as a water reducer. Water can be reduced up to 20%, depending on the quality of fly ash as well as the amount of cement replaced and therefore, act as a superplasticizing admixture when used in high-volume (Mehta, 2004). Besides that, using fly ash makes concrete more workable. This is because the concrete gets more cohesive and the occurrence of costly segregation decreases when less amount of water is needed for the same slump (Bremseth,

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