Search

V okviru diplomske naloge je bil razvit in izdelan merilec za merjenje volumenskih deformacij v cementni malti. Merilec je omogočal začetek merjenja takoj po vgraditvi v togi brezšivni jekleni kalup valjaste oblike, torej je bilo omogočeno spremljanje razvoja deformacij, ki se razvijejo v prvih urah po zamešanju cementne malte. Meritve so bile opravljene na čisti cementni malti in na malti, kateri je bila dodana kontrolirana količina aeranta. Aerant je bil uporabljen kot sredstvo za nastanek ciljne mikrostrukture cementne malte. Potrjena je bila hipoteza, da stabilizirani zračni mehurčki nudijo neomejen prostor za neovirano in intenzivno rast kristalov CH in etringita na obodu mehurčka in povzročijo volumensko ekspanzijo cementne matrice v začetni fazi hidratacije, ki je bistveno večja, kot pa je ekspanzija malte brez aeranta. V kasnejši fazi hidratacije pa zračni mehurčki vplivajo na intenzivnejše krčenje. Tendenca izmerjenih rezultatov notranjih deformacij, tako ekspanzije kot tudi krčenja, se giblje v skladu z navedbami literature. In the presented diploma thesis the device for measurement of volumetric deformations on cementitious mortars was developed and manufactured. The device enabled starting the measurements immediately after casting of fresh mortars into rigid cylindrical steel molds, which gives a possibility of recording the early-age deformations. Two experimental mortar mixes were used: plain cement mortar and the mortar with addition of air entraining agent (AEA). The addition of AEA caused the formation of the microstructure with finely dispersed air bubbles forming an unlimited space for growth of CH crystals and ettringite. The formation of ettringite and CH crystals is considered as a principal cause of early-age expansion much higher on mortars with AEA. Subsequent shrinkage was found to be also more intense on mortars with AEA. The results of measurements performed in this study are in accordance with findings of literature.