Diagnosing the causes of clay hollow bricks degradation embedded in the reinforced concrete ceiling
| Autor: | Samo Lubej, Boris Lutar |
|---|---|
| Rok vydání: | 2013 |
| Předmět: |
clay hollow bricks
mikrostrukture termične analize votle glinene opeke microstructure delayed ettringite formation udc:691 zapoznelo oblikovanje entringita šuplji opečni blokovi mikrostruktura zakašnjelo stvaranje entringita (DEF) mehanička svojstva toplotna analiza mechanical properties thermal analysis mehanske lastnosti |
| Zdroj: | E-GFOS, no. 6, pp. 96-107, 2013. Electronic Journal of the Faculty of Civil Engineering Osijek-e-GFOS Volume 4 Issue 6 |
| ISSN: | 1847-8948 |
| DOI: | 10.13167/2013.6.9 |
| Popis: | U konstrukciji montažnih stropova od šupljih opečnih blokova, koji su element ispune između nosivih armiranobetonskih greda, u razdoblju od četiri godine poslije njihove izgradnje došlo je do znatnih oštećenja. Oštećenja stropova manifestirala su se odlamanjem dijelova šupljih opečnih blokova, što je ugrožavalo sigurnost ljudi. Uporabom optičkog mikroskopa i elektronskog mikroskopa, kao i kemijske mikroanalize EDS (Energy Dispersive System), analizirana je oštećena keramika te je utvrđena prisutnost iskristalizirane soli. EDS analizom utvrđena je prisutnost kemijskih elemenata (Al i S), koji uz utvrđenu morfologiju kristala ukazuju na mogućnost prisutnosti minerala etringita (Al2O33CaSO4 x 32H2O). Numeričkom analizom uz primjenu metode konačnih elemenata, uporabom računalnog programa COSMOS Design STAR 3.0 od SRAC (Structural Research and analisis Corporation USA), procijenjen je utjecaj temperaturnih opterećenja na koncetraciju naprezanja na vrhu mikropukotina i na njihovo širenje. U numeričkoj analizi eksperimentalno su uzeta u obzir određena fizikalno- mehanička svojstva materijala. Analizirani su primjeri šupljih opečnih blokova s prisutnošću bijelih kristala i bez njih. Prikazan je raspored faktora sigurnosti po modelu u odnosu na Mises-ovu hipotezu razaranja. Rezultati eksperimentalnih i numeričkih istraživanja pokazali su da kemijska degradacija šupljih opečnih blokova, u kombinaciji s temperaturnim opterećenjem koje nastaje zbog promjena klimatskog režima, može uzrokovati takva oštećenja te da je time ugrožena i sigurnost konstrukcije. Over a two-year period following the construction completion extensive damage has occurred in the mountable brick ceilings at the University of Maribor administrative quarters. The damage of the ceilings consisted in falling pieces of brick filling - construction ceramics, which presented a potential hazard to people. Using the optical as well as electronic microscope methods combined with chemical analysis EDX (Energy Dispersive X-Ray Analysis) we confirmed the presence of the white crystals, which could be mineral ettringite (Al2O33CaSO4 x 32H2O) that can, when present in construction ceramics, cause degradation of matter through expansion. By means of numerical analysis using final elements method and by means of the COSMOS Design STAR 3.0 computer software (by SRAC - Structural Research and Analysis Corporation USA) we were able to experimentally determine effects of temperature fluctuation. The experimentally assessed physical-mechanical characteristics of the material were considered in the numerical analysis. Both cases, brick filling containing the white crystals and brick filling without white crystals were analysed. The safety factor distribution on the model according to Mises demolition hypothesis was shown. It was confirmed on basis of experimental research that the chemical degradation of construction ceramics combined with temperature fluctuation due to climate changes, even without considering degradations due to technological production process, can lead to such damage in the material as to cause a safety hazard. |
| Databáze: | OpenAIRE |
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