Search Results
Abstract
This paper presents the results of investigation of properties of fly ash from four major thermal power plants in Serbia. Chemical, mineralogical and thermal characterization of fly ash has been performed in order to determine the possibility of its use as the raw material for the construction material industry, primarily the cement industry. Thermal properties of the raw mixtures for Portland cement clinker production based on fly ash were also investigated. The conclusion was reached that the use of fly ash as a component of the raw mixture components for the production of cement clinker not only enables substitution of natural raw materials, but could also have a positive influence on reduction of the sintering temperature of Portland cement clinker.
Introduction Over 50% of the 3.3 billion tonnes of coal, annually produced in China, are used for power generation, which results in the generation of over 0.4 billion tonnes of fly ash [ 1 ]. Only about 30% of produced fly ash
Investigations of cement early hydration in the presence of chemically activated fly ash
Use of calorimetry and infrared absorption methods
Abstract
The paper describes an attempt of chemical activation of fly ash and claims the usefulness of combination of such investigation methods as calorimetry and infrared absorption for investigations of early periods of cement hydration. The research samples were cement pastes made with an addition of fly ash and admixtures of chemical activators, CaCl2, Na2SO4 and NaOH, whereas a cement paste without fly ash addition and a cement-fly ash paste (both without admixtures) were used as reference samples. In order to investigate early periods of cement pastes hydration, the amount and rate of heat release were registered, and IR spectrums were checked at appointed hydration moments. As a result, it was shown that the combination of calorimetric and IR absorption methods in the investigations of early periods of cement hydration was useful. It was confirmed that the use of chemical activators CaCl2, Na2SO4 and NaOH accelerated the hydration of cement pastes containing fly ash additive in early hours after adding water. The action of activators on hydrating cement system is different for each of investigated compounds.
Abstract
The calorimetric data of binders containing pure Portland cement, 20% fly ash, 20% slag and 10% silica fume respectively are determined at different initial casting temperatures using an adiabatic calorimeter to measure the adiabatic temperature rising of concrete. The calorimetric data of binders with different dosages of fly ash at two water binder ratios (w/b) are determined, too. Elevation of initial casting temperature decreases the heat evolution of binder, enhances the heat evolution rate of binder and increases the heat evolution rate of binder at early age. The dosage of fly ash in concrete has different effects on the heat evolution of binder with different w/b. At high w/b ratio the heat evolution of binder decreases when dosage of fly ash increases. At low w/b ratio the heat evolution of binders increases when dosage of fly ash increases from 0 to 40% of total binder quantity. The heat evolution of binder decreases after the dosage of fly ash over 40%. An appropriate dosage of fly ash in binder benefits the performance of concrete at low w/b ratio.
, generated worldwide from thermal coal-fired powers [ 1 ]. The current annual production of the coal ash worldwide is estimated around 600 million tones with fly ash about 500 million tones [ 2 ]. Although effective measures have been taken in utilizing fly
Pattanaik Ch. S, Sabat K. A. A study of Nalco fly ash on compressive strength for effective use in high volume mass concrete for a sustainable development . India: Mumbai, 2010. Sabat K. A
Introduction Fly ash, a by-product from coal power plants, has been recognized as an important construction material due to its environmental benefits and engineering benefits (produce less heat of hydration, increase
Abstract
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.
Introduction Fly ash and fluorgypsum are industrial waste. In 2008, nearly 400 million tons of fly ash has been produced by coal-burning power plants in China. And it is estimated that this number would exceed 500 million at
, researchers continue to explore as fly ash has material and pozzolanic properties required for construction [ 6–11 ]. Fly ash from power plants contain traces of Ca, Mg, Na and K that makes it unfit for the agricultural purpose and further makes it harder to
