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[en] This study is principally concerned with characterizing the organic part of coal combustion fly ashes. High carbon fly ashes are becoming more common as by-products of low-NOx combustion technology, and there is need to learn more about this fraction of the fly ash. The project team consists of two universities, Brown and Princeton, and an electrical utility, New England Power. A sample suite of over fifty fly ashes has been gathered from utilities across the United States, and includes ashes from a coals ranging in rank from bituminous to lignite. The characterizations of these ashes include standard tests (LOI, Foam Index), as well as more detailed characterizations of their surface areas, porosity, extractability and adsorption behavior. The ultimate goal is, by better characterizing the material, to enable broadening the range of applications for coal fly ash re-use beyond the current main market as a pozzolanic agent for concretes. The potential for high carbon-content fly ashes to substitute for activated carbons is receiving particular attention. The work performed to date has already revealed how very different the surfaces of different ashes produced by the same utility can be, with respect to polarity of the residual carbon. This can help explain the large variations in acceptability of these ashes as concrete additives
[en] Potentially acid forming (PAF) materials are encapsulated with non-acid forming materials (NAF) in order to prevent acid mine drainage (AMD) in surface coal mines. NAF compaction techniques with fly and bottom ashes from coal-fired power plants are used in mines with limited amounts of NAF materials. This study investigated the weathering behaviour of blended overburden and coal combustion ash in laboratory conditions. Free draining column leach tests were conducted on different blending schemes. The weathering process was simulated by spraying the samples with de-ionized water once per day. The leachates were then analyzed using X-ray diffraction and fluorescence analyses in order to identify the mineral composition of the samples over a 14 week period. Results of the study indicated that the weathering process plays a significant role in controlling infiltration rates, and may increase the capability of capping materials to prevent infiltration into PAF materials. Fly- and bottom-ash additions improved the performance of the encapsulation materials. 3 refs., 4 tabs., 2 figs.
[en] Production in Poland and applications of industrial radiometric instruments have been performed. The several group of instruments have been presented in detail; level measuring devices, densimeters, thickness gages, weight indicators, concentration of H2SO4 measuring device, dust meters, ash content and coal quality analysers and other measuring and automation systems. The future development directions in construction of radioisotope measuring instruments has been also discussed
[en] Low concentrations of uranium and thorium are present in coal. After the combustion of the coal U and Th almost completely concentrate in fly ash. Because of the fact that radioactivity and ionizing radiation are emotionally charged subjects the radiation protective aspects of the storage and processing of fly ash results in many misunderstandings. The study on the title subject is aimed at informing the public on the ionizing radiation aspects of fly ash, and to consider the consequences of the government regulations in this field. The extra radiation burden for fly ash workers is maximal 5-10% of the natural background radiation, which is far below the legal standard. The standard for other members of the population will even be much lower. Still, there are no insurmountable problems regarding the storage of fly ash and its application in the road construction
[en] Starting from measuring values of radioactivity, toxicity, as well as from models of food chains, radionuclide migration and deposition, irradiation doses are calculated in case of release of fly ash to the environment (e.g. from building materials). (orig.)
[en] Highlights: • Eco-Core sandwich beam is flexural fatigue tested to study its fatigue response. • The core showed three failure types: damage onset, progression and final failure. • These failures were found to be represented by 1%, 5% and 7% change in compliance. • The fatigue stress-life (S–N) relationship follows a power low, σmax/σct = AoNα. • The fatigue failure was by multiple vertical cracks followed by 45° shear failure. - Abstract: Eco-Core is a class of syntactic foam made from small volume of high char yield binder and large volume of a class of flyash for fire resistance application. Very little or no flexural fatigue data of this class of core material is reported in the open literature. This paper presents a flexural fatigue response of Eco-Core in a glass/vinyl ester composite face sheet sandwich beam. A four-point loaded flexural test specimen was designed and tested in static and fatigue loadings to cause tension failure in the core. The fatigue test was conducted at maximum cyclic stress (σmax) ranged from 0.7σct to 0.9σct, where σct is the static flexural strength of the core. The sinusoidal loading frequency of 2 Hz with the stress ratio of 0.1 was used. Flexural fatigue failure modes of Eco-Core sandwich beam were classified: damage onset (single tension crack), damage progression (multiple tension cracks) and ultimate failure (a combination of tension and shear). These failures were characterized by 1%, 5% and 7% changes in compliance that corresponds to N1%, N5% and N7% lives. The fatigue stress-life (S–N) relationship was found to follow the well-known power law equation, σmax/σct = AoNα. The constants Ao and α were established for all three types of failures. The endurance limit was established based on 1 million cycles limit and it was found to be 0.65σct, 0.70σct and 0.71σct, respectively for the three modes of failure. Flexural fatigue and static failure modes of Eco-Core sandwich beams were similar
[en] Strontium aluminosilicate, SrAl2Si2O8 (SAS), was synthesized by a solid state reaction using coal fly ash (CFA) as main raw material. A precursor mixture of SrCO3, CFA and Al2O3 was mechanically-activated for times of up to 12 h using an attrition mill, and subsequently sintered at temperatures of 900-1300 degree centigrade. The CFA and the mechanical activation were employed with the aim to promote the transformation from the hexagonal (Sr-Hexacelsian) into the monoclinic (Sr-Celsian) polymorphic form of SAS, since the latter phase is associated with better physical and mechanical properties but the former tends to be the first one to appear. The mean particle size, the crystallite size and the temperature at the end of the curve of weight loss (Tf) decreased, while the specific surface area and the degree of amorphization increased, with increasing milling time. Samples milled for at least 4 h and then sintered at 1100 degree centigrade achieved full transformation into Sr-Celsian. The same result was obtained for sintering temperatures higher than 1100 degree centigrade, independently of milling time. An increment in both the milling time and the sintering temperature allowed us to improve the densification and the mechanical properties of the synthesized materials. (Author) 24 refs.
[en] With the purpose of evaluating the radioactive contamination that it cause the solid residuals of the coal taken place during their combustion in the thermal power stations of Paipa, Zipaquira, Tasajero and Guajira, it was determined respectively by the methods of neutronic activation and slowed neutrons the concentration of 232Th and 238U, in the flying ashes and scum. These techniques were applied in the facilities of the INEA (today Ingeominas) to the samples gathered in the project ICEL-UNIVALLE. In these ashes the radioactive concentration was determined that in accordance with the UNSCEAR (Scientific Committee of the United Nations for the study of the Effect of the Atomic Radiations), indeed they cause emissions and emanations to the atmosphere and that they are considered bigger than the opposing ones in the natural bottom of the terrestrial bark; these they are intensified due to the elimination of the organic component of the coal, when becoming ash, increasing the radioactive concentration in an order of magnitude
[en] The mini-slump test is a fast, inexpensive and widely adopted method for evaluating the workability of fresh cementitious pastes. However, this method lacks a standardised procedure for its experimental implementation, which is crucial to guarantee reproducibility and reliability of the test results. This study investigates and proposes a guideline procedure for mini-slump testing, focusing on the influence of key experimental (mixing and testing) parameters on the statistical performance of the results. The importance of preparation of always testing at the same time after mixing, testing each batch once rather than conducting multiple tests on a single batch of material, is highlighted. A set of alkali-activated fly ash-slag pastes, spanning from 1 to 75 Pa yield stresses, were used to validate the test method, by comparison of calculated yield stresses with the results obtained using a conventional vane viscometer. The proposed experimental procedure for mini-slump testing produces highly reproducible results, and the yield stress calculated from mini-slump values correlate very well with those measured by viscometer, in the case of fresh paste of pure shear flow. Mini-slump testing is a reliable method that can be utilised for the assessment of workability of cements.