Hydration Of Fly Ash Research Articles

97/04266 Heat of hydration of fly ash as a predictive tool

97/04266 Heat of hydration of fly ash as a predictive tool

Reduced fertility among women exposed to organic solvents : M. Sallmen, M.-L. Lindbohm, P. Kyyronen, E. Nykyri, A. Anttila, H. Taskinen, K. Hemminki. American Journal of Industrial Medicine 27(5), 699–713, May 1995

The ternary effects of nanosilica/polycarboxylate ether superplasticizer nanocomposite ([email protected]), graphene oxide (GO) and fly ash (FA) with different dosages on workability, fly ash hydration, water sorptivity, compressive strength and microstructure development of cement paste were investigated. The results revealed that the [email protected] addition improves the workability of cement paste significantly. The single addition of [email protected] or GO have favorable effect on hydration of FA particle, whereas the hybrid of both in cement cause a bit loss of the FA hydration degree (FA HD). 1% of [email protected] addition and 0.01% of GO dosages in FA-blended cement are sufficient for compensate its early strength loss caused by the FA incorporation. Microstructure investigation verified the formation of new polyhedron-like crystals, with an average length of 1.25 µm and Ca/Si ratio of 12.99, in cement of 28 days.

Heat of hydration of fly ash as a predictive tool

A test procedure based on heat of hydration was developed to assess more accurately the reactivity and behaviour of fly ash for utilization. The technique uses a Dewar flask or a modified oxygen bomb calorimeter to determine the temperature change and rate of change after the addition of water to fly ash. X-ray diffraction is performed on the hydrated material after the hydration test to follow mineralogical changes due to the hydration process. A study of coal ash samples is under way to determine whether correlations exist between the temperature change and results from empirical tests, such as those of the ASTM, used to determine properties of ash for engineering applications. A protocol has been developed for an improved classification scheme for coal ash.

96/03211 - Fly ash hydration with quicklime for improving sorbent utilization and SO 2 removal in spray dryer absorbers

96/03211 - Fly ash hydration with quicklime for improving sorbent utilization and SO 2 removal in spray dryer absorbers

Fly Ash Reactivation for the Desulfurization of Coal-Fired Utility Station's Flue Gas

Abstract Fly ash hydration in the liquid phase has been studied by employing temperature, hydration time, and water/fly ash weight ratio as variables. The results show that temperature and hydration time have a large positive effect in surface area development of the hydrated ashes (due to the formation of hydrated tetracalcium aluminate) whereas the water/fly ash weight ratio effect seems to be negative but its influence is very small. Desulfurization tests have been carried out with some of these hydrated fly ashes. Tests consisted of exposing the solid for 1 h to an N2/SO2 gas stream containing 500 ppm SO2. The variables employed were temperature and relative humidity. The results show that SO2 capture rises with temperature and, particularly, with an increase in relative humidity. A correlation between surface area and SO2 capture was found. The greater the surface area, the greater the amount of SO2 captured. This fact shows that hydrated tetracalcium aluminate is a highly reactive substance against SO2.

Microstructural study of gypsum activated fly ash hydration in cement paste

The addition of 3 to 6% gypsum to a low alkali, low C 3A cement blended with low (30 %) and high (60%) volume of a Class F fly ash (FA) led to a distinct increase in strength in comparision to the blends without additional gypsum. This is discussed in terms of the reaction of the FA with cement and gypsum. The role of FA alkalies is also described. The investigation included scanning electron microscopy/energy dispersive X-ray analysis (SEM/EDXA) to study the microstructural development of FA replacement pastes with progressive hydration, and X-ray diffraction (XRD) for mineralogical identification of hydrated phases.

Quantatative determination of pozzolanas in hydrated systems of cement or Ca(OH) 2 with fly ash or silica fume

A selective dissolution method using a slightly modified picric acid-methanol-water solution procedure was found to be adequate for the quantitative determination of unhydrated fly ash and silica fume in hydrated systems of cement-fly ash and cement-silica fume, respectively. The extent of hydration of fly ash and silica fume in various paste mixtures has been calculated. The hydration products and the residue composition were examined by both X-ray diffraction and energy-dispersive X-ray analysis and their morphologies were observed under an SEM.

Effectiveness of research on fly ash in concrete

Energy crises and availability have for a decade funded extensive research and numerous conferences regarding uses of fly ash in concrete. The returns of these investments can be improved by more systematic characterisation of fly ashes and of cements used with them, and by more conceptual approaches to further development of testing methods, incorporating exploration of the energetics of fly ash hydration with cement and of the ways in which fly ash may improve the microstructure of cement paste, whether hydrated or as “micro-aggregate”. Suggestions are presented for desirable changes of the planning of research and communication of research results.