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Beton je v modernem svetu nepogrešljiv in najbolj razširjen gradbeni material. Na svetovni ravni se proizvede približno 4 tone betona na prebivalca na leto in proizvodnja se z leti neprestano povečuje. Do konca leta 2050 naj bi bila po nekaterih izračunih 4 x višja kot v letu 1990. Emisije povezane s pridobivanjem betona predstavljajo 5–7 % vseh svetovnih CO2 izpustov. Poleg tega spremljajo cementno industrijo velika poraba naravnih surovin, onesnaževanje, ter vrsta drugih okoljskih problemov. Ena izmed možnih rešitev povezanih s cementno proizvodnjo je recikliranje različnih odpadnih gradbenih materialov. Namen magistrske naloge je bil analiza in določevanje nekaterih odpadnih gradbenih materialov za mineralne dodatke (MD). Osredotočili smo se na naslednje odpadne materiale: betone, odpadni cement, keramiko, sanitarno keramiko in siporeks. Na 5 različnih odlagališčih odpadkov po Sloveniji (Novo mesto, Maribor, Slovenj Gradec, Izola in Ljubljana) smo pobrali vzorce omenjenega materiala in ga analizirali. Vzorce smo razbili na manjše kose (kjer je bilo potrebno ločili cement od agregata), jih zmleli v prah in analizirali z rentgensko praškovno difrakcijo (XRD), rentgensko fluorescenco (XRF), vrstično elektronsko mikroskopijo (SEM), diferenčno dinamično kalorimetrijo (DSC) in termogravimetrično metodo (TG). Rezultati so pokazali dober potencial testiranih vzorcev za MD. Glede na analiziran material pridobljen iz odpadnega betona, bi lahko za namen reaktivacije najprej uporabili kalcit in dolomit. Poleg tega je uporaben tudi ves prisotni amorfni material, ki ga bi bilo mogoče temperaturno reaktivirati. Večino materiala, ki ga z XRD analizo zaznamo kot amorfno fazo pripada namreč CSH (CSH kalcijev silikat hidrat glavni produkt hidratacije portlandskega cementa). V vseh vzorcih preučevane keramike je bilo prisotno veliko kremena, albita, mulita in amorfne faze. Kremen, albit in mulit so precej stabilni in kot taki predstavljajo odlični polnilni material, amorfni del pa reagira v cementnih reakcijah, zaradi česar je keramika odličen MD. Vzorci sanitarne keramike imajo precej podobno mineralno in kemijsko sestavo kot vzorci keramike, edina bistvena razlika je v glazuri, ki prekriva sanitarno keramiko. Glazura vsebuje večje količine natrija in kalija, ki še dodatno pomagata pri pucolanskih reakcijah. Analizirani siporeks je izmed testiranih gradbenih odpadkov prikazal najboljši potencial za uporabo kot MD, saj je vseboval pretežno kremen in amorfno fazo ter majhne deleže aluminija. Odpadni cement je primeren za ponovno uporabo ob temperaturni reaktivaciji. Prevladujoči komponenti sta bili amorfna faza 47 % in alit 35 % . Concrete is an indispensable and most widespread building material in the modern world. For every person in the world, about 4 tons of concrete is produced annually, the production of which is further increased every year. By the end of 2050, it is estimated to be 4 x higher than in 1990. Emissions from concrete production account for 5–7 % of global CO2 emissions. In addition, the cement industry is accompanied with raw material consumption, pollution and a number of other environmental problems. One possible solution that lowers cement production is recycling of the waste construction materials. Purpose of this master’s thesis was to analyse some of the waste construction materials and to evaluate them as potential supplementary cementitious materials. We focused on the following waste materials: concrete, waste cement, ceramics, sanitary ware and Siporex. Samples of the mentioned materials were collected and analysed at 5 different landfills in Slovenia (Novo mesto, Maribor, Slovenj Gradec, Izola and Ljubljana). The samples were broken into smaller pieces (where it was necessary to separate the cement from the aggregate) and ground into a powder. We analysed the samples by X-ray diffraction, X ray fluorescence, scanning electron microscope, differential scanning calorimetry and thermogravimetry. The results showed that the tested samples could be used for supplementary cementitious materials (SCM). Depending on the material analysed from waste concrete calcite and dolomite could be used for reactivation purposes. In addition, amorphous material present could be heat reactivated. In fact, most of the material detected by XRD analysis as amorphous phase belongs to CSH (CSH-calcium silicate hydrate, which is the main product of the hydration of Portland cement). In all the ceramic samples, quartz, albite, mullite and the amorphous fraction were present in high abundance. The quartz, albite and mullite are quite stable and as such constitute an excellent filler material, while the amorphous fraction reacts in cementitious reactions, making the ceramics as an excellent SCM. Mineral and chemical composition of the sanitary ware is very similar to ceramic samples, the only significant difference being the glaze covering the sanitary ware. The glaze contains higher amounts of sodium and potassium, which helps with the pozzolanic reactions. Analysed Siporex showed the best potential for SCM use. It contained predominantly quartz and an amorphous phase, and only a small amount of aluminium. Waste cement can be directly reused upon temperature reactivation. The predominant components were 47% amorphous phase and 35% alite. |
