Special Concretes: Enhancement of Resistance to Aggressive Media Using Fly Ash and Admixtures Featuring Pozzuolana Characteristics

摘要

This paper presents findings of testing focused on resistance enhancement of special concretes (SCC, HPC, RPC) as well as common concrete (C) through application of secondary raw material (fly ash) and admixtures featuring pozzuolana characteristics (metakaolin). The tests were aimed at examination, comparison, analyzing and evaluation of admixture of fly ash and/or metakaolin respectively at influence thereof on above mentioned special concretes exposed to various chemical aggressive media. Analyzed concretes were stored in aggressive liquid media (SO_4~(2-), Cl~-, engine lubrication oil), gaseous media (simulated concentration of CO_2, SO_2 under various relative humidity), along with reference samples in aqueous media as specified by appropriate standards. After 3, 6, 9 and 12 months, particular concretes passed through physico-mechanical and physico-chemical analyses i.e. the concretes were tested as to physico-mechanical and physico-chemical properties, appearance, and condition after the exposure to particular aggressive media. After 12 months of such treatment, no physico-mechanical parameters of special concretes modified by fly ash and metakaolin were deteriorated. Surprisingly, SCC modified by fly ash and HPC modified by metakaolin achieved markedly better parameters when compared with identical concretes without application of fly ash and metakaolin. RPC modified by fly ash, when compared with unmodified RPC, featured inferior to a certain extent nevertheless, these properties did not reduce resistance of that concretes to particular chemical aggressive media. However, common concretes made with fly ash admixture achieved markedly inferior physico-mechanical parameters that demonstrated themselves through diminished resistance to the tested chemical aggressive media.