Rheological properties of cement paste

U ovom radu istražena su svojstva Portland cementa klase G namijenjenog cementiranju naftnih bušotina. Rotacijskim viskozimetrom izmjerena su reološka svojstava svježe cementne paste uz dodatak superplastifikatora u masenim udjelima od 0,4 do 1,1 % na masu cementa. Ovisnost smičnog naprezanja o smičnoj brzini pripravljenih pasti uspješno je opisana Herschel-Bulkleyevim modelom. Reopektna svojstva cementnih pasti smanjuju se dodatkom superplastifikatora, te su paste sve sličnije Newtonovskom fluidu. Rendgenskom difrakcijskom analizom određen je fazni sastav cementa i produkata hidratacije cementnih pasti uz dodatak superplastifikatora nakon 24 h i 28 dana pri sobnoj temperaturi. Tijek hidratacije cementnih pasti uz dodatak superplastifikatora praćen je kalorimetrijskim mjerenjem tijekom 120 h pri 22 °C, te je ustanovljeno da dodatak superplastifikatora odgađa hidrataciju alita za 6-12 h.In this thesis, the properties of Portland cement grade G are researched for the purpose of cementing oil wells. The rotational viscometer measured the rheological properties of the fresh cement paste with the addition of superplasticizers in mass ratio of 0.4 to 1.1 % on the cement mass. The dependency of shear stress and shear rate has been successfully described by Herschel-Bulkley's model. The rheopectic properties of cement pastes are reduced by the addition of superplasticizers, and the paste is more similar to Newton's fluid. By X-ray diffraction analysis, the phase composition of cement and cementitious hydration products was determined with addition of superplasticizer after 24 h and 28 days at room temperature. The flow of cement paste hydration with the addition of superplasticizer was determined by calorimetric measurement for 120 h at 22 ° C, and it was found that superplasticizer addition delayed the alite hydration for 6-12 h