Calciumaluminatecements are hydraulic binders of special properties and applications. They are mainly applied in production of fire-resistant materials but this kind of cement is also useful in cases when
Calorimetric studies of Portland cement [ 1 , 2 ] and calciumaluminatecement [ 3 , 4 ] pastes show that the FCC catalyst remarkably influences the hydration of various cements. It has been found that, in the compositions with Portland cement, the FCC
Calciumaluminatecements (CACs) are quickly hardening hydraulic binders, which significantly differ in their chemical and phase compositions, properties and applications from often used Portland cements. They
Calciumaluminatecement (CAC) is known as an indispensable material in the construction field for its resistance to chemical attack and high temperatures [ 1 ]. In the dry-mix mortar industry, such as self
The most widely identified degradation process suffered by calcium aluminate cement (CAC) is the so-called conversion of hexagonal
calcium aluminate hydrate to cubic form. This conversion is usually followed by an increase in porosity determined by the
different densities of these hydrates and the subsequent loss of strength. Mixes of calcium aluminate cement (CAC) and silica
fume (SF) or fly ash (FA) represent an interesting alternative for the stabilization of CAC hydrates, which might be attributed
to a microstructure based mainly on aluminosilicates. This paper deals with the microstructure of cement pastes fabricated
with mixtures CAC-SF and CAC-FA and its evolution over time. Thermal analysis (DTA/TG), X-ray diffraction (XRD) and mid-infrared
spectroscopy (FTIR) have been used to assess the microstructure of these formulations.
To use flue gas desulfurization (FGD) gypsum and limestone as supplement of cement, conduction calorimetry was applied to
investigate the early hydration of ternary binder of calcium aluminate cement (CAC), Portland-limestone cement (PLC), and
FGD gypsum, supplemented with the determination of setting times and X-ray diffraction (XRD) analysis. Different exothermal
profiles were presented in two groups of pastes, in which one group (group A) sets the mass ratio of FGD gypsum/CAC at 0.25
and the other group (group B) sets the mass ratio of PLC/CAC at 0.25. Besides the two common exothermal peaks in cement hydration,
a third exothermal peak appears in the pastes with 5–15% FGD gypsum after gypsum is depleted. It is found that not PLC but
FGD gypsum plays the key role in such ternary binder where the reaction of ettringite formation dominates the hydration process.
PLC accelerates the hydration of ternary binder, which mainly attributes to the nucleating effect of fine limestone particles
and PC clinker. The modified hydration process and mechanism in this case is well visualized by the means of calorimetry and
it helps us to optimize such design of ternary cementitious material.
The use of by-product gypsum is an important alternative in concrete design. In present experiment, conduction calorimetry
was applied to investigate the early hydration of calcium aluminate cement (CAC)/flue gas desulfurization (FGD) gypsum paste,
supplemented with the determination of setting times and analysis of hydrates by X-ray diffraction (XRD). It was found that
different profiles of heat evolution rate were presented depending on the CAC/FGD gypsum ratio. Two distinct exothermic peaks,
associating with CAC hydration and ettringite formation respectively, appeared when the FGD gypsum content was less than 20%.
Hydrate barrier mechanism was introduced to explain the difference in induction periods of the pastes with or without FGD
gypsum. It is concluded that the blending of FGD gypsum accelerates the hydration of CAC for the quick formation of ettringite
and generates greater hydration heat from per gram of pure CAC for the high exothermic effect of ettringite formation. The
dissolution and diffusion of gypsum plays an important role of reacting controller during the hydrations of the pastes with
FGD gypsum. The modified hydration process and mechanism in this case is well visualized by means of calorimetry.
The aim of this work is to compare the influence of addition of waste aluminosilicate catalyst on the initial periods of hydration
of different cements, i.e. calcium aluminate cements of different composition and Portland cement, basing on the calorimetric
studies. Cement pastes containing up to 25 mass% of additive were studied, where the water/(cement+additive) ratio was 0.5.
An attempt was undertaken to explain the mechanism of action of introduced aluminosilicate in the system of hydrating cement,
particularly in the case of calcium aluminate cement pastes.
It was found that the presence of fine-grained additive caused in all studied cases the increase of the amount of released
heat in the first period after the addition of water. In the case of aluminate cements with aluminosilicate addition, a significant
reduction of induction time and faster precipitation of hydration products were observed compared to the reference sample
(without additive). In the experimental conditions, the additive caused the acceleration of aluminate cements hydration, and
the mechanism of its action is probably complex and can encompass: nucleative action of small grains and formation of new
Calorimetry has been used in the investigations of calcium aluminate materials produced as a binder for aluminate-corundum
composites of high refractoriness. The kinetics and of hydration process was thus characterized and the optimum compositions
of initial binders and cement-corundum refractory filler blends could be selected for further tests. The acceleration of heat
evolution - the shortening of so-called induction period and relatively high heat output in the presence of corundum was observed.
It means the acceleration of hydration process, that is early crystallisation of hydration products and subsequent further
dissolution of initial anhydrous aluminate phases. In the presence of fine grained corundum particles these phenomena should
be attributed to the nucleating effect of fine corundum particles.
Calorimetry was applied to an investigation of the early hydration of Portland cement (PC)–calcium aluminate cement (CAC)
pastes. The heat evolution measurements were related to the strength tests on small cylindrical samples and standard mortar
bars. Different heat-evolution profiles were observed, depending on the calcium aluminate cement/Portland cement ratio. The
significant modification of Portland cement heat evolution profile within a few hours after mixing with water was observed
generally in pastes containing up to 25% CAC. On the other hand the CAC hydration acceleration effect was also obtained with
the 10% and 20% addition of Portland cement. As one could expect the compressive and flexural strength development was more
or less changed—reduced in the presence of larger amount of the second component in the mixture, presumably because of the
internal cracks generated by expansive calcium sulfoaluminate formation.