Reuse Of Micronized Fly Ashes In High Strength Cement Conglomerates
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G. Belz, P. Caramuscio, G. Intini, L. Liberti, C. Marti & M. Notarnicola
In this paper the experimental results of an investigation carried out in collaboration with ENEL (the Italian Company for electric energy) on the use of micronized fly ash from coal combustion as pozzolanic material for production of high strength cement conglomerates are presented. The grinding of fly ash was carried out in ball, ring and jet mills; the size distribution of micronized material was similar to silica fume, normally used to produce high performance conglomerates due to its very high specific surface. Mechanical strength tests were performed on mortars with different substitution of cement or sand (between 10 and 30 % in weight) with micronized fly ash (MFA), raw fly ash (RFA) and silica fume (SF) respectively. The water/cement ratio (w/c) was regulated to obtain equal workability of the pastes (from 0,35 to 0,4). The values of compression and bending strength of mortars prepared with MFA were not greatly influenced by the quantity of substituted material and water content present in the mortar. Moreover, good mechanical performance was obtained in shorter times than RFA, with a behaviour similar to more expensive SF. The results obtained show that the improved chemico-physico-mechanical characteristics of micronized fly ash make feasible the reuse of this by-product in high strength cement conglomerates. Keywords: fly ash, coal combustion, grinding treatment, cement conglomerates. 1 Introduction Fly ash from coal combustion in power plants can either be considered as a burdensome waste, if landfilled, or a great resource for a wide range of uses, if
fly ash, coal combustion, grinding treatment, cement conglomerates.