Search results for "fly ash"
showing 10 items of 53 documents
Characterization by solid-state NMR and selective dissolution techniques of anhydrous and hydrated CEM V cement pastes.
2010
International audience; The long term behaviour of cement based materials is strongly dependent on the paste microstructure and also on the internal chemistry. A CEM V blended cement containing pulverised fly ash (PFA) and blastfurnace slag (BFS) has been studied in order to understand hydration processes which influence the paste microstructure. Solid-state NMR spectroscopy with complementary X-ray diffraction analysis and selective dissolution techniques have been used for the characterization of the various phases (C3S, C2S, C3A and C4AF) of the clinker and additives and then for estimation of the degree of hydration of these same phases. Their quantification after simulation of experime…
Prediction of Long-Term Chemical Evolution of a Low-pH Cement Designed for Underground Radioactive Waste Repositories
2012
Low-pH cements, also referred as low-alkalinity cements, are binders with a pore solution pH ≤ 11. They can be designed by replacing significant amounts of Portland cement (OPC) (≥40 %) by silica fume, which can be associated in some cases to low-CaO fly ash and/or ground granulated blast furnace slag to decrease the heat output during hydration by dilution of OPC and improve the mechanical strength of the final material. With the prospect of using these materials in a geological repository, it is of main importance to estimate their long-term properties and the influence of external and internal factors (chemical composition of the binder, storage temperature) on their characteristics. For…
Effect of superplasticizers on the rheological properties of fly ash suspensions containing activators of the pozzolanic reaction
2000
Rheological studies have been carried out on the effect of a superplasticizer from the sulphonated melamine formaldehyde (SMF) group upon the properties of fly ash suspensions containing a small quantity of mineral admixtures such as cement, lime and gypsum. The superplasticizers' efficiency has appeared to depend greatly on the admixture used. The highest liquefaction degree was found in fly ash suspensions containing both cement and gypsum together and the next it was, when only cement was added. These suspensions exhibit features of a newtonian fluid of low plastic viscosity, when the water to solid ratio (w/s) is 0.3 and a superplasticizer has been used. However, fly ash suspensions wit…
Optimization of Radioactive Waste Cementation for Decommissioning of Salaspils Research Reactor
2011
This paper deals with information on the radioactive waste cementation technology for decommissioning of Salaspils Research Reactor (SRR). Dismantled and segmented radioactive materials were cemented in concrete containers using tritiated water-cement mixture. The viscosity of water-cement mortar, mechanical tests of solidified mortar’s samples, change of temperature of the samples during solidification time and long time leakage of 137Cs, 14C, 60Co and 3T radionuclides was studied for different water-cement compositions with additives. The pH and electro conductivity of the solutions during leakage tests were controlled. It was shown, that water/cement ratio significantly influences on wat…
Effect of content and particle size distribution of high-calcium fly ash on the rheological properties of cement pastes
1997
Abstract The Theological properties of high-calcium fly ash cement pastes were investigated. An increase both in yield value and plastic viscosity with fly ash content was found. It was also observed that the pastes became more fluid with the higher fly ash fineness. A more important relation was shown between the fine fractions (
Development of a performance threshold approach for identifying the management options for stabilisation/solidification of lead polluted soils
2014
Two soils spiked with lead at different rates were stabilised/solidified using Portland cement and fy ash at different soil:binder ratios, and tested for their setting time, unconfined compressive strength, leachability and durability. A performance threshold approach was used in order to identify optimal management options for the products of the S/S treatment. Results show that soil texture, percentage of binders and lead concentration play an important part in the treatment, significantly influencing the performance of the resulting products in terms of curing, compressive strength and durability. Pb soil concentrations higher than 15000 mg kg-1 were found to heavily reduce the applicab…
ICP-MS multielement determination in fly ash after microwave-assisted digestion of samples.
2001
A microwave assisted digestion procedure has been developed for dissolution of fly ash samples prior to the inductively coupled plasma-mass spectrometric determination of their elemental composition. The developed methodology was validated by carrying out the analysis of two high-silicate containing reference materials (CRM 134R sewage amended soil and NIES JR 1 rock) and by means of the comparison between results found by microwave-assisted digestion and ICP-MS of fly ash samples with those found by neutron activation analysis (NAA) for Sb, Cs, Cr, Co, Fe, U and Zn determination. The method developed can be recommended for routine multielement analysis of fly ash.
Alkali-activated mortars for sustainable construction material: effects of binder-to-aggregate ratio and curing conditions
2019
Valorisation and reuse of industrial wastes has become a worldwide compelling topic to improve the sustainability of processes and materials. This paper discusses an alternative way to recycle the biomass fly ash, generated by the kraft pulp industry, to manufacture novel geopolymeric mortars intended for applications in construction. Biomass fly ash was used as a raw material, in partial substitution of the commonly used metakaolin, natural siliceous sand as aggregate. The followed manufacture process is highly simple and reproducible. Various proportions binder to aggregate were tested to study the effect on the final mortars properties. The mortars mechanical resistance was also studied …
ALKALI-ACTIVATED MORTARS FOR SUSTAINABLE CONSTRUCTION MATERIAL: EFFECTS OF BINDER-TO- AGGREGATE RATIO AND CURING CONDITION
2019
Valorisation and reuse of industrial wastes has become a worldwide compelling topic to improve the sustainability of processes and materials. This paper discusses an alternative way to recycle the biomass fly ash, generated by the kraft pulp industry, to manufacture novel geopolymeric mortars intended for applications in construction. Biomass fly ash was used as a raw material, in partial substitution of the commonly used metakaolin, natural siliceous sand as aggregate. The followed manufacture process is highly simple and reproducible. Various proportions binder to aggregate were tested to study the effect on the final mortars properties. The mortars mechanical resistance was also studied …
Technogenic Magnetic Particles in Alkaline Dusts from Power and Cement Plants
2012
During this study, we investigated the mineralogical characterization of technogenic magnetic particles (TMPs) contained in alkaline industrial dust and fly ash emitted by coal burning power plants and cement plants. The reaction of tested dust samples varied between values of pH 8 and pH 12. Their magnetic properties were characterized by measurement of magnetic susceptibility (χ), frequency dependence of magnetic susceptibility (χ(fd)), and temperature dependence of magnetic susceptibility. Mineralogical and geochemical analyses included scanning electron microscopy with energy dispersive spectroscopy, microprobe analysis and X-ray diffraction. The TMPs in fly ash from hard coal combustio…