Cement hydration with addition of ash from biomass combuston

Abstract

U ovom radu istražena je kemija hidratacije cementa uz dodatak letećeg pepela koji nastaje kao nusprodukt pri spaljivanju drvne biomase. Leteći pepeo sadrži relativno veliki udio slobodnog kalcij oksida (CaO), larnita (β-C2S) i brownmillerita (C4AF), minerala karakterističnih za portland cement. S ciljem priprave novih ekoloških veziva istražen je utjecaj dodatka letećeg pepela na hidrataciju i svojstva pripravljenih cementnih materijala metodama XRD, TGA i kalorimetrije te je ispitana konzistencija i volumna postojanost cementne paste. Utvrđeno je da hidratacijom čistog pepela nastaje uglavnom C4AHx, a smanjenje udjela Ca(OH)2 ukazuje na hidratnu i pucolansku reaktivnost pepela. Kod hidratacije cementa maksimum udjela Ca(OH)2 postiže se pri sedmom danu, dok s dodatkom pepela, dolazi do smanjenja količine Ca(OH)2 nakon sedam dana hidratacije uslijed pucolanske reakcije. Rezultati ukazuju na moguću oporabu i korištenje pepela biomase u cementnim materijalima što doprinosi smanjenju uporabe prirodnih sirovina i manjem utjecaju na okoliš.This work investigates chemistry of cement hydration with addition of fly ash from biomass combustion. Fly ash contains a relatively large part of free calcium oxide (CaO), larnite (β-C2S), and brownmillerite (C4AF), minerals found in portland cement. Hydration and properties of new ecological cement binders prepared with fly ash addition had been investigated by X-ray diffraction (XRD), thermogravimetric analysis (TGA) and calorimetry. Consistency and volume stability of cement paste were also investigated. It was found that pure ash hydration produces mainly C4AHx and reduced content of Ca(OH)2 indicates pozzolanic and hydraulic reactivity of the ash. In case of pure cement hydration the Ca(OH)2 content reaches its maximum on the 7th day. After seven days the reduction of Ca(OH)2 content is a result of a chemical reaction with pozzolanic active ingredients present in already mixed cement. The results indicate to the possibility of using the ash from biomass in new ecological cement binders, which contributes to a lower use of natural raw materials and lower impact on the environment