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Author index ►Carlos Eduardo Carbone, Roberto Cesar de Oliveira Romano, Maria Alba Cincotto, Rafael Giuliano Pileggi
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Hardening stage evaluation of white Portland cements using oscillatory and compressive rheometry, isothermal calorimetry and the Vicat test
Appl. Rheol. 28:1 (2018) 16396 (9 pages) ►
White Portland cement can be used such as decorative coatings, masonry regularization as the skin coat, and many other applications mainly due to the ease of association with pigments to confer coloring to the applied products for aesthetic purposes. Despite of the evaluation of the hardened stage properties to be more commonly found in literature, just a few published works monitored the transition from fluid-to-solid stage, but this is an important step because it defines the performance of products over time. The main purpose of this work was to compare the consolidation of different types of white Portland cement during the hardening stage, i.e. using a combined evaluation of the chemical and physical phenomena. Isothermal conduction calorimetry was the method used to monitor the heat release during the hydration reaction and oscillatory and compressive rheometry were applied to monitor the changes in workability over time. The setting time, measured by Vicat test represents the open time of each composition and was evaluated because it is affected by the physicochemical changes of the cement. Despite the obtained results are standardized, they are empirical/arbitrary by nature. Three brands of white Portland cements (CauêAalborg, and Tolteca) were chosen and their suspensions were prepared to achieve a constant watercement ratio of 0.5. All suspensions presented shear thinning behavior, but different levels of yield stress and apparent viscosity. The Tolteca cement presented the fastest heat release, which impacted the gain on consistency as measured by oscillatory rheometry or the loss of workability as measured by the squeeze flow test. The combined evaluations, i.e. physical and chemical results indicated that despite the fact that the changes during the hardening process had been affected: Correlations were only observed in the physical parameters indicating that the hydration reaction promotes random changes in the microstructure development.► Cite this publication as follows:
Carbone CE, Romano RCdO, Cincotto MA, Pileggi RG: Hardening stage evaluation of white Portland cements using oscillatory and compressive rheometry, isothermal calorimetry and the Vicat test, Appl. Rheol. 28 (2018) 16396.
Roberto Cesar de Oliveira Romano, Marcel Hark Maciel, Rafael Giuliano Pileggi, Maria Alba Cincotto
Monitoring of hardening of Portland cement suspensions by Vicat test, oscillatory rheometry and isothermal calorimetry
Appl. Rheol. 27:3 (2017) 36006 (10 pages) ►
The hardening of cement pastes occurs due to coagulation/flocculation promoted by the hydration reactions. At this way, depending on the physico-chemical characteristics of the powder, different changes are obtained during the microstructure formation. Thus, as the use of supplementary cementitious materials is rising worldwide, this stage of construction process is being more complex. So, this work was conducted to evaluate the hardening phenomenon of pastes formulated with Portland cements blended with limestone filler (LF) and ground blast furnace slag (BFS). Vicat test, oscillatory rheometry and isothermal conduction calorimetry were used to monitor this transition. Vicat test results indicate different setting times as a function of addition, but no information before these times was obtained. Using isothermal calorimetry was possible to monitor the related changes to the chemical reactions since the first contact with water, and using rheometry, the rate and force of cement particle agglomeration. During the discussion of results will be not presented in depth the results of the three methods, but will be shown that they are complementary and provide a better explanation to the transition from fluid-to-solid behavior, independently of kind of supplementary cementitious materials.► Cite this publication as follows:
Romano RCdO, Maciel MH, Pileggi RG, Cincotto MA: Monitoring of hardening of Portland cement suspensions by Vicat test, oscillatory rheometry and isothermal calorimetry, Appl. Rheol. 27 (2017) 36006.
Roberto Cesar de Oliveira Romano, Caio Cesar Liberato, Marcelo Montini, Jorge Borges Gallo, Maria Alba Cincotto, Rafael Giuliano Pileggi
Evaluation of transition from fluid to elastic solid of cementitious pastes with bauxite residue using oscillation rheometry and isothermal calorimetry
Appl. Rheol. 23:2 (2013) 23830 (9 pages) ►
This work evaluates the impact of using bauxite residue (BR) as filler addition in cementitious compositions, during the early ages of transformation from the viscous fluid phase to an elastic solid. Chemical reaction and consolidation (physical phenomena of hardening) were also correlated. The chemical reaction rate was accompanied using isothermal calorimetry and the consolidation measured using oscillatory rheometry (quantifying the storage modulus - G' and relating with yield stress, σ0). The results show that BR accelerates the cement hydration reaction, but in pastes with pure cement, consolidation was faster, showing a distinct effect on the fluid-solid transition.► Cite this publication as follows:
Romano RCdO, Liberato CC, Montini M, Gallo JB, Cincotto MA, Pileggi RG: Evaluation of transition from fluid to elastic solid of cementitious pastes with bauxite residue using oscillation rheometry and isothermal calorimetry, Appl. Rheol. 23 (2013) 23830.
Roberto Cesar de Oliveira Romano, Rafael Giuliano Pileggi
Temperature's role in the rheological behavior of cementitious pastes prepared with air-entraining admixtures
Appl. Rheol. 22:2 (2012) 24333 (6 pages) ►
Cementitious pastes prepared with air-entraining admixtures (AEA) are very sensitive to mix procedures and environmental conditions. Some of the effects of AEA on the properties of cementitious material are discussed in literature, although for the most part, only in the hardened state. However, the impact temperature has on air-incorporation during the early age stages and on consolidation has been little investigated and as such, is the objective of this work. Thus, pastes formulated with Portland cement and air-entraining admixtures are evaluated in this work with a focus on the role temperature plays in the early age behavior. The results show that air-incorporation was affected by environmental conditions which caused changes in the kinematic viscosity and rate of consolidation.► Cite this publication as follows:
deOliveiraRomano RC, Pileggi RG: Temperature's role in the rheological behavior of cementitious pastes prepared with air-entraining admixtures, Appl. Rheol. 22 (2012) 24333.
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