Carbonation of alkaline activated slag (AAS): a comparison with Portland cement

Reference	Presenter	Authors (Institution)	Abstract
04-045	Caroline Angulski da Luz	Kretschmer, L.C.(UTFPR); Pereira, H.L.(UTFPR); Bortolozzo, P.H.(UTFPR); Angulski da Luz, C.(UTFPR); Perardt, M.(UTFPR); Mantelli, D.F.(Universidade Tecnológica Federal do Paraná); Volkweis, L.(UTFPR);	Granulated blast furnace slags (GBFS) are by-products from pig iron manufacturing process, and widely used as supplementary cementing materials (SCMs) to Portland cement (PC) to obtain GBFS-Cement blends. In Brazil, PC can have up to 70% of GBFS to obtain CP type III which presents good properties in relation to sulfate resistance. On the other hand, alkaline activated cement (AAC) can be obtained from wastes such as fly ash or even GBFS, which are activated by solutions of sodium hydroxide (NaOH), potassium hydroxide (KOH) or silicates, without calcination process. AAC obtained from GBFS are denominated alkaline activated slag (AAS). In addition to its good environmental properties, AAS also present good mechanical characteristics. Then, the goal of this study was to contribute to investigations about durability of AAS, in this case, carbonation. AAS was obtained from GBFS which was activated by 5% of NaOH. Concretes were made using AAS and two types of Portland cement (IV and V) as comparison. After 28 days, all concretes were carried to the compressive strength and carbonation depth tests using phenolphthalein and thymolphthalein solutions. Void index and absorption test was conducted to AAC and PC IV concrete samples. All samples were exposed to external (natural) conditions. The 3 month carbonation depth measure was already taken to PC concretes. The 28 day-results indicated carbonation on AAC samples, probably due to exudation of the NaOH solution. PC IV and PC V samples were not carbonated and AAC concrete compressive strength was similar to PC IV. AAC concrete showed higher void index than PC IV during saturation at room temperature, but was slightly lower after boiling procedure, which indicates a higher penetration in AAC concrete in the initial ages and stabilization after aging.
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