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This study analyses the effect of fluidised bed cracking catalyst (FBCC) waste, milled to nano-sizes and unmilled, on the hydration of calcium aluminate cement after hardening under normal conditions and after thermal treatment of the samples at 1200 °C. Differential thermal analysis (DTA), X-ray analysis (XRD), and electron scanning microscopy analysis (SEM) were conducted. Results of calorimetry studies showed that milled FBCC added up to 5% slightly slows down the hydration processes of aluminate cement, whereas 10% of FBCC accelerates the hydration. The total amount of heat released in the samples with milled FBCC was lower than that in the samples with unmilled FBCC. The thermogravimetry analysis (TG) revealed higher mass loss in samples with unmilled FBCC. Additionally, XRD results after hardening showed that, compared to the samples with unmilled FBCC, the samples with milled FBCC yielded a higher relative intensity of unreacted minerals of cement. After burning the samples at 1200 °C, anorthite crystals were formed in the samples with FBCC. The effect of unmilled FBCC on the hydration process was explained by the ability of the particles to absorb water at the initial hydration stage and subsequently to transfer it to further hydration steps, thereby promoting the formation of crystallohydrates in larger quantities. [ABSTRACT FROM AUTHOR]

This paper deals with the design, synthesis, hydration mechanism and hydration products of novel Ba2+-, Cu2+- or Bi3+-doped CaO–Al2O3–ZrO2-based cementitious materials used for heavyweight concrete mixes. The results of the heating microscopy thermal analysis indicated that both Cu and Bi in a Ca7ZrAl6O18-based cement clinker can effectively reduce the sintering temperature by 150–200 °C. Incorporation of barium for the synthesis of calcium zirconium aluminate-based hydraulic binder increased its thermal resistance since Ba2+-doped Ca7ZrAl6O18 along with accessory (Ca,Ba)ZrO3 with a perovskite‐type structure and BaAl2O4 phases having high melting points were formed. The presence of metal ions, i.e., Cu2+ or Bi3+, created conditions which were favorable for the formation of hexagonal calcium aluminate hydrates rather than the cubic one, as confirmed by coupled DSC–TG/EGA–MS thermal analysis techniques and X-ray diffraction. For the Ba2+ doping ions, this effect was the least noticeable. The effect of metal ions including Ba2+, Cu2+ and Bi3+ on microstructural features of cement pastes was investigated by SEM–EDS. These doping ions strongly affected the morphologies of Ca–Al hydrates. [ABSTRACT FROM AUTHOR]

In the paper, the impact of paper-mill sludge dried at 75 °C (PS) on cement hydration is being analysed. The used specimens were made of CEM I 42.5 R cement and the added PS replaced 0%, 5%, 10% and 15% by mass of cement. The results of calorimetric measurements of the mixtures and the compressive strength were analysed (W/(C + PS) = 0.35). SEM and XRD tests were carried out after 3, 14, 28 and 56 days of curing W/(C + PS) = 1. PS was found to extend the induction period of the cement hydration and delay the time of the secondary heat release effect, especially in specimens with the highest content of the PS. The total heat release (after 96 h) measurement results showed that the highest total heat evolved from specimens without the PS. The total liberated heat gradually increased with the increase in the PS content in the cement paste mixture. In the specimens with 15% of PS, the total heat release decreased by 20%, as compared to the control specimen without the additive. XRD test results revealed that the standard minerals listed below were formed in cement stone: ettringite, calcite, portlandite, and calcium aluminium silicate hydrate. SEM tests revealed significant changes in cement stone microstructure caused by the increase in the PS in cement paste. The compressive strength of specimens with PS waste was found to be considerably lower in the initial stage of hardening; however, when samples hardening time is increased up to 56 days, the difference between the values of compressive strength for specimens 5% of PS and the control specimens decreases. [ABSTRACT FROM AUTHOR]

The article analyses the peculiarities of the combined effect on hydration process of the following pozzolanic additives: metakaolin waste (MW), material generated in the manufacture of expanded glass granules (GEG) and fluidized bed cracking catalyst waste (FCCW), as well as melamine-based superplasticizer (SP). Mixes with and without GEG containing two types of waste were tested. Peculiarities of hydration process were evaluated from the results of calorimetry, SEM and mechanical properties tests. The effect of pozzolanic additives and SP was analysed according to strength activity index (SAI). Test results revealed that synergistic effect of MW and FCCW was significant and practically relevant. These pozzolanic additives have a different effect on hydration process, yet when both waste materials are used together, it is possible to control the progress of hydration process. Besides, specimens with GEG and additive of both waste materials demonstrated the highest SAI index. The results of calorimetry tests of cement paste and plaster modified with plasticizer were different. Active metakaolin particles present on GEG surface significantly slow down the hydration process. [ABSTRACT FROM AUTHOR]

The shelf life of cement and cement-based dry mixtures is often determined by ageing of such materials. The ageing is the result of interactions between cement and other components of cementitious mixtures with moisture as well as with CO from the atmosphere. In this work, the ageing behaviour of calcium aluminate cement and its mixtures with additives of microsilica, fluidized catalytic cracking catalyst waste and ground quartz sand were investigated. The ageing was achieved by storing cement and its mixtures in a climatic chamber for 7 and 14 days at 95% relative humidity and 20 ± 1 °C temperature. Applying thermal analysis, XRD analysis as well as scanning electronic microscopy, it was established that hydration of the cement minerals takes place along with carbonation during the ageing process of cement and its mixtures. The quantities of the products formed during ageing and their crystallinity depend on the nature of additives and the duration of ageing. When applying the method of calorimetric analysis, the influence of ageing on the kinetics of hydration of cement and as well as of its mixtures with the additives used in the work has been established. [ABSTRACT FROM AUTHOR]

The effect produced by the short carbon fiber additive on the hydration of calcium aluminate cement under the ambient temperatures of 10, 20 and 30 °C is investigated. The calorimetric analysis of the cement paste has shown that the carbon fiber additive increases heat release and decreases the induction period of hydration at the ambient temperatures of 10 and 30 °C, while at the temperature of 20 °C, this period is increased. X-ray diffraction and thermal analysis have shown that carbon fiber additive does not have any influence on the composition of the formed hydrates; however, their amount depends on it. It has been also found that a dense layer of cement hydrates is formed around the fibers. Due to the positive effect of carbon fiber additive on cement hydration and microstructure, as well as its reinforcing effect, the compressive strength and the bending strength of cement stone are increased by 3-23 and 13-70 %, respectively, depending on the ambient temperature. [ABSTRACT FROM AUTHOR]