Determination of glass content and estimation of glass composition in fly ash using quantitative X-ray diffractometry

The proportion of amorphous or glassy material in a series of fly ashes has been evaluated by X-ray powder diffraction (XRD) using the Rietveld-based SIROQUANT software package. Several different sample preparation and processing methods were investigated, including XRD analysis of samples spiked with known masses of synthetic corundum and zinc oxide as well as techniques based on analysing the raw or unspiked fly ash directly using the SIROQUANT process. In the latter case, two different poorly crystallised silicate mineral patterns, metakaolin and tridymite, were used in the SIROQUANT processing of the raw ash XRD data to represent the amorphous constituents. The results of the different methods based on XRD of spiked samples were found to be mutually consistent, and also consistent with other published data for an international reference fly ash sample. SIROQUANT analysis of the unspiked fly ashes gave similar results, although different poorly crystallised silicate reference patterns seem to be more suited for ashes from Australian and North American sources.The mineralogy of the ashes, including the proportions of quartz, iron oxide and glassy constituents, appears to be related to the nature of the mineral matter in the relevant feed coals. Calculations based on subtracting the inferred chemistry of the crystalline minerals in the fly ashes from the total fly ash chemistry were also used to estimate the overall chemical composition of the glass fraction in each ash. The results indicate that ashes derived from lower-rank coals in the samples studied have different glass compositions to those derived from higher-rank (bituminous) materials. These different glass compositions appear to be related to several other ash properties, including particle density and particle surface area. Evaluation of glass content and composition may be significant in different aspects of ash utilisation, and also in evaluating interactions with water at ash disposal sites.     

大掺量粉煤灰对混凝土渗透性的影响

以粉煤灰代替３０％的水泥，在水胶比为０．３０、０．３３、０．３６及０．３９的情况下，分别试验了用水量及胶凝材料用量变化下混凝土的强度和渗透性。试验结果表明，与不掺粉煤灰的混凝土比较，掺粉煤灰混凝土的渗透性都明显降低，３０天龄期时最大可降低至５０．７％，７０天时可降低至２２．３％；为了获得较低的渗透性而采取较低的水胶比时，不掺粉煤灰的混凝土应用降低用水量的办法有利，掺粉煤灰的混凝土用提高总胶凝材料用量的办法更好     

Pheromone-mediated copulatory responses of the screwworm fly,Cochliomyia hominivorax

A bioassay based on male copulatory responses occurring on contact with dead decoy insects was used to confirm the existence of a sex pheromone in the screwworm fly,Cochliomyia hominivorax. Males responded to female but not male decoys. Mated and virgin females were equally stimulatory. Activity was abolished when females were washed with hexane but partially restored by treatment with crude hexane extract of females. Responses decreased when extracts were diluted and when the number of females extracted per milliliter of hexane was decreased from 20 to 1 in the preparation of extracts concentrated to 0.4 female/l. Sexually mature female decoys of the 009 strain, the most laboratory-adapted of three strains examined in intrastrain tests, produced few copulatory attempts compared with those of Aricruz or DE-9 strains. However, newly emerged 009 as well as Aricruz females elicited responses from about 80% of sexually mature males. Those of the DE-9 strain stimulated fewer than 1%. The observation that 009 females were maximally stimulatory before becoming receptive to mating suggests that these strain differences resulted from laboratory colonization.     

混合材对水泥与减水剂适应性的影响研究

通过对掺高效减水剂水泥净浆流动性及流动性损失的测定试验，研究了3种混合材(粉煤灰、水淬高炉矿渣和沸石)在不同替代率情况下对减水剂作用效果的影响。结果表明：水淬高炉矿渣有利于改善减水剂与水泥的适应性，而掺粉煤灰和沸石(尤其是沸石)则会导致减水剂塑化作用的降低，而且浆体流动性损失也有增大趋势。     

Alkali release characteristics of blended cements

This paper presents results of an experimental program conducted to investigate the capacity of hydration products of different cementing materials to retain “bound” alkalis when the alkalinity of the surrounding solution drops. The study covered paste samples containing high-alkali Portland cement and various levels of silica fume and/or fly ash. The results showed that the ability of the hydration products of cement-fly ash systems to bind alkalis is a function of the CaO content of the fly ash, the binding increasing as the calcium content decreases. High-alkali fly ashes (Na₂O_e > 5.0% and CaO in the range of 15% to 20%) showed considerable amounts of alkali contributed to the test solutions. Silica fume does not have a high capacity to retain alkalis in its hydration products; however, ternary blends containing silica fume and fly ash have excellent capacity to bind and retain alkalis.     

Sex-specific activity of (R)-(−)- and (S)- (+)-1,7-dioxaspiro[5.5]undecane,the major pheromone ofDacus oleae

1,7-Dioxaspiro[5.5]undecane (olean), the major component of the female sex attractant pheromone blend of the olive fruit flyDacus oleae (Gmelin) was shown to be released as a racemate. The response of males and females to pure (R)-(–) and (S)-(+)-enantiomers was tested under laboratory and field conditions. Males in laboratory and field tests responded only to (R)-(–)-olean, which functions as a sex attractant. Females responded only to (S)-(+)-olean in laboratory tests but not in the field. There are indications that the latter enantiomer fuctions as a short-range arrestant throughout the day and as an aphrodisiac in the process of mating.Diptera: Tephritidae.     

合成煤中钠对煤燃烧及灰特性影响

准东煤中钠含量高，燃用时锅炉会出现严重结渣问题。通过向准东煤为原料制取的超纯煤中添加灰的模型化合物，得到合成煤。并在此基础上利用热重-差示扫描量热分析法（TG/DTG/DSC）、X射线衍射仪（XRD）和灰熔融温度测定分析手段，研究Na₂O含量对煤燃烧特性和灰熔融性的影响。结果表明：钠主要影响合成煤的着火温度（T_i）与焦炭燃烧阶段，钠含量增加使T_i升高，并且Na₂O在灰中质量分数由5%升高至8%后，钠含量增加使焦炭燃烧速率先减小后加快，并能够改善煤粉燃尽特性。钠能够降低灰熔融温度，并在Na₂O质量分数高于5%后，温度下降更加明显。在三元相图中钠对莫来石的助熔作用是造成灰熔融温度降低的重要原因。XRD分析表明Na₂O含量增加，充当骨架作用的石英在钠的助熔作用下与难熔矿物硅钙石、MgO等生成低熔点长石类矿物，这类矿物在高温下有助熔作用，能够降低灰熔融温度。同时还生成助熔性含钠矿物霞石，加剧了灰熔融。     

Electrodialytic extraction of Cu,Pb and Cl from municipal solid waste incineration fly ash suspended in water

The possibility of using fly ash from municipal solid waste incineration (MSWI) in, for example, concrete is considered. MSWI fly ash, however, has too high a concentration of heavy metals, which may cause leaching problems during use or problems with waste handling at the end of the lifetime of the concrete. The Cl content in MSWI fly ash is also too high and will cause corrosion problems in reinforced concrete. The possibility of removing some of the unwanted heavy metals (Cu and Pb) together with Cl from an MSWI fly ash suspended in water using an electrodialytic separation method was investigated. The removal of Pb and Cu was found to be highly pH dependent and the highest contents removed were 41 and 90%, respectively. The Cu concentration of the ash decreased from 2200 to 860 mg kg^?1 but the Pb concentration increased from 8560 to 16 800 mg kg^?1, showing that Pb is mainly found in the ash fraction that is least soluble. Hence electrodialytic treatment of the ash suspended in water is not a solution to improve the ash quality in terms of Pb. The water‐soluble Cl content per unit weight of the original ash was 12.4%. The removal of water‐soluble Cl was efficient and >98% of Cl was removed (calculated on the basis of mean initial and final concentrations). This result indicates that electrodialytic extraction may be a method that can be used for the removal of Cl from ash prior to its utilization in concrete. Copyright © 2006 Society of Chemical Industry     

Effect of porous structure and surface functionality on the mercury capacity of a fly ash carbon and its activated sample

The effect of porous structure and surface functionality on the mercury capacity of a fly ash carbon and its activated sample has been investigated. The samples were tested for mercury adsorption using a fixed‐bed with a simulated flue gas. The activated fly ash carbon sample has lower mercury capacity than its precursor fly ash carbon (0.23 vs. 1.85 mg/g), although its surface area is around 15 times larger, 863 vs. 53 m²/g. It was found that oxygen functionality and the presence of halogen species on the surface of fly ash carbons may promote mercury adsorption, while the surface area does not seem to have a significant effect on their mercury capacity.     

Prediction model of compressive strength development of fly-ash concrete

Based on experimental results concerning the compressive strength development of concrete containing fly ash, the authors derived an estimation equation for compressive strength development. The equation can express coefficient , which indicates the activity of fly ash as a binder, in the form of a function of age, fly-ash content, and Blaine specific surface area of fly ash.

This equation is capable of explaining the increases in the early strength due to fly ash in place of part of fine aggregate, the decreases in the early strength due to fly ash in place of part of cement, the increases in the long-term strength due to pozzolanic reaction, the relationship between the fly-ash replacement ratio and the ratio of strength increase/decrease, and the effect of fly ash's Blaine specific surface area on the strength.