Ash Rate Research Articles

Analysis of thermally activated kinetics and uniformity of photoresist ashing process on 300 mm wafers

Ashing rate and nonuniformity are the usual parameters used for the evaluation of industrial ashers. A detailed study of the wafer temperature and of its effect on the two contributions to the diminution of photoresist thickness, namely, shrinkage and chemical reactions, gives a solid ground for understanding the variations of ashing rate with process conditions. It is in particular shown how variations of shrink with temperature affect the measured ashing rate. This analysis serves as a basis for proposing tests that could be used as “standards” and ease the objective comparison of industrial ashers, based on real performances. They include a determination of ashing rate on hard-baked wafers for characterization of radical density, a demonstration of the ion-free nature of the process, and a determination of wafer heat-up rate. Due to the very reproducible nature of the distribution of ashing rates over a wafer, it is argued that the “range” parameter should be used over standard deviation for the measurement of nonuniformity within a wafer.

Simulation of a temperature rise in concrete incorporating fly ash or slag

Granulated slag from metal industries and fly ash from the combustion of coal are among the industrial by-products and have been widely used as mineral admixtures in normal and high strength concrete. Due to the reaction between calcium hydroxide and fly ash or slag, compared with Portland cement, the hydration of concrete containing fly ash or slag is much more complex. In this paper, by considering the producing of calcium hydroxide in cement hydration and the consumption of it in the reaction of mineral admixtures, a numerical model is proposed to simulate the hydration of concrete containing fly ash or slag. The heat evolution rate of fly ash or slag blended concrete is determined from the contribution of both cement hydration and the reaction of mineral admixtures. Furthermore, a temperature rise in blended concrete is evaluated based on the degree of hydration of cement and mineral admixtures. The proposed model is verified with experimental data on the concrete with different water-to-cement ratios and mineral admixtures substitution ratios.

Photosynthetic Pigment Concentrations, Gas Exchange and Vegetative Growth for Selected Monocots and Dicots Treated with Two Contrasting Coal Fly Ashes

There is uncertainty as to the rates of coal fly ash needed for optimum physiological processes and growth. In the current study we tested the hypothesis that photosynthetic pigments concentrations and CO(2) assimilation (A) are more sensitive than dry weights in plants grown on media amended with coal fly ash. We applied the Terrestrial Plant Growth Test (Guideline 208) protocols of the Organization for Economic Cooperation and Development (OECD) to monocots [barley (Hordeum vulgare) and ryegrass (Secale cereale)] and dicots [canola (Brasica napus), radish (Raphanus sativus), field peas (Pisum sativum), and lucerne (Medicago sativa)] on media amended with fly ashes derived from semi-bituminous (gray ash) or lignite (red ash) coals at rates of 0, 2.5, 5.0, 10, or 20 Mg ha(-1). The red ash had higher elemental concentrations and salinity than the gray ash. Fly ash addition had no significant effect on germination by any of the six species. At moderate rates (</= 10 Mg ha(-1)) both ashes increased (p < 0.05) growth rates and concentrations of chlorophylls a and b, but reduced carotenoid concentrations. Addition of either ash increased A in radish and transpiration in barley. Growth rates and final dry weights were reduced for all of the six test species when addition rates exceeded 10 Mg ha(-1) for gray ash and 5 Mg ha(-1) for red ash. We concluded that plant dry weights, rather than pigment concentrations and/or instantaneous rates of photosynthesis, are more consistent for assessing subsequent growth in plants supplied with fly ash.

Recycling of Waste Concrete and Fly Ash for Recycled Aggregate Concrete: Fundamental Characteristics Evaluation

As the amount of waste concrete has been increased and recycling technique advances, this study investigates the applicability of recycled concrete aggregate for concrete structures. In addition fly ash, the industrial by-product, was considered in the concrete mix. Experimental program performed compressive strength and chloride penetration resistance tests with various replacement levels of fine recycled concrete aggregate and fly ash. In most case, the design strength, 40MPa, was obtained. It was known that the replacement of the fine aggregate with fine RCA may have greater influence on the strength development rather than the addition of fly ash. It is recommended that when complete coarse aggregate is replaced with RCA the fine RCA replacement should be less than 60%. The recycled aggregate concrete can achieve sufficient resistance to the chloride ion penetration and the resistance can be more effectively controlled by adding fly ash. It I finally conclude that the recycled concrete aggregate can be successfully used in the construction field and the recycling rate of waste concrete and flay ash should be increased without causing significant engineering problems.

Tree mortality in a mixed deciduous forest in Northwestern Russia over 22 years

• We studied mortality rates of birch, small-leaved linden, pedunculate oak, Norway maple, black alder, common ash and Norway spruce, assessed through two inventories of 12 664 trees in the unmanaged mixed deciduous forests of Oranienbaum Park, northwestern Russia, in 1981 and 2003. • Our objectives were to evaluate if (a) long-term mortality rates vary among species, and if (b) crown condition, age and tree size affect the probability of mortality. • Over this period, tree mortality rates in the park varied annually from 1 to 3% for healthy and moderately healthy trees, and from 3.9 to 9.3% for declining trees. The lowest mortality rates were observed for small-leaved linden and oak (0.8 and 1.0%, respectively), and the highest rate for birch (2.7%). We found (1) a significant and consistent association between tree condition and the probability of mortality, and (2) significantly higher mortality rates in smaller trees of ash, maple and oak. • The effect of species-specific biology on mortality rates in the Oranienbaum Park was largely overridden by the “health status” and environmental conditions of the trees (e.g. degree of crown shading). The observed rates were similar to the estimates from natural temperate deciduous forests in both Europe and North America, indicating similar intensity of mortality in these ecosystems under natural conditions.

An experimental study on the hazard assessment and mechanical properties of porous concrete utilizing coal bottom ash coarse aggregate in Korea

This study evaluates quality properties and toxicity of coal bottom ash coarse aggregate and analyzes mechanical properties of porous concrete depending on mixing rates of coal bottom ash. As a result, soundness and resistance to abrasion of coal bottom ash coarse aggregate were satisfied according to the standard of coarse aggregate for concrete. To satisfy the standard pertaining to chloride content, the coarse aggregates have to be washed more than twice. In regards to the result of leaching test for coal bottom ash coarse aggregate and porous concrete produced with these coarse aggregates, it was satisfied with the environment criteria. As the mixing rate of coal bottom ash increased, influence of void ratio and permeability coefficient was very little, but compressive and flexural strength decreased. When coal bottom ash was mixed over 40%, strength decreased sharply (compressive strength: by 11.7–27.1%, flexural strength: by maximum 26.4%). Also, as the mixing rate of coal bottom ash increased, it was confirmed that test specimens were destroyed by aggregate fracture more than binder fracture and interface fracture. To utilize coal bottom ash in large quantities, it is thought that an improvement method in regards to strength has to be discussed such as incorporation of reinforcing materials and improvement of aggregate hardness.

Describing growth and predicting feed intake in the marine prawn Fenneropenaeus indicus: Part I: Theoretical and practical aspects of measuring and predicting genetic parameters

Monitoring and predicting growth and feed intake of cultured aquatic animals is a significant problem in aquaculture. The present study examines the potential of an approach based on potential accretion rate of body protein to predict live weight gain and feed requirement of the marine prawn, Fenneropenaeus indicus. The protein accretion rate was predicted using the Gompertz equation while the growth of body components and nutrient gains therein was established using allometric relationships. Live weight gain was determined by summing the accretion rates of body protein, lipid, water, ash and carbohydrate. The model parameters included the protein content at maturity (Pd m , [mg]), the rate of maturing ( β, [/d]), the maximum rate of protein deposition (Pd max , [mg day − 1 ]), the lipid to protein ratio at maturity (LPR m , [Ld m :Pd m ]), ash (APR m ,[Ad m :Pd m ]), water (WAPR m ,[WAd m :Pd m ]) and carbohydrate to protein ratio at maturity (CPR m ,[Cd m :Pd m ]), and the exoskeleton to flesh ratio (E:F). To generate information to establish these parameters, feeding trials with prawn were carried out in indoor tanks and an outdoor growout pond. Juveniles from the same brood stock were allowed to grow to adults under conditions assumed ideal. Tank reared animals failed to obtain similar growth to those cultured in the pond. Values for the above parameters for a mixed batch of pond reared prawns were estimated to be 6541 mg, 0.014/d, 32.68 mg day − 1 , 0.03, 0.20, 3.30, 0.06 and 1:3.6, respectively when reared at 19–27 °C and 21–27‰. Results indicated that the model proposed here, derived from and based on research in higher vertebrates, was well suited to describing the genotype of F. indicus reared under semi-intensive conditions. This study is, to our knowledge, the first to examine and describe mathematically the rates of body lipid, ash, water and carbohydrate accretion in prawns as a function of protein gains in the flesh and exoskeleton of F. indicus.

Cultivo de Ankistrodesmus gracilis (Chlorophyta) em laboratório à base de esterco suíno

Ankistrodesmus gracilis (Chlorophyta) fertilized in swine manure in the laboratory. The objective of the present work was to investigate the infl uence of swine manure media on the growth, total length, dry weight, and nutrit- ional value of Ankistrodesmus gracilis microalgae. Two media were mea- sured: “in natura” and biodigested. The growth rate peak for A. gracilis was highest with biodigester treatment (6.2 x 107 cells.mL-1) on the 5th day, at a volume of 2L. The highest percentage of lipids was verifi ed for “in natura” media. Protein was highest (p &gt; 0.05) for the biodigested media at 2L. Biovolume, ash rate, and total length were different (p &lt; 0.05) between treatments, but the same was not true for dry weight and crude fi ber (p &gt; 0.05). Light demand was also different between media, with lesser intensity being required for biodigested media (13.5μE.cm-2.s- 1). In fact, the biodigested media proved to be cheaper in terms of cost and benefi t. Generally, the medium containing swine manure, both “in natura” and biodigested, showed better results in A. gracilis development, with water quality adequate for culture systems. Swine manure in both forms may also be used in high-density cultures in the laboratory.

The burning characteristics of southeastern oaks: Discriminating fire facilitators from fire impeders

In southeastern pine–oak ecosystems, ecological restoration targets oaks for removal by chemical, mechanical, burning, or combinations of treatments. Managers often pursue oak removal indiscriminately despite the poorly understood historical structure, cover, and ecological function within these ecosystems. Restoration treatments often cite the impediment that oak litter represents to prescribed fire spread and effectiveness. We evaluated the burning characteristics of eight southeastern Quercus spp. by burning collected litter under controlled conditions in a combustion chamber. Replicated burns consisted of 15 g of litter on a 35 cm × 35 cm grid of xylene-soaked cotton strings. Burning characteristics measured included maximum flame height (cm), flaming duration (s), smoldering duration (s), residual ash, and mass loss rate (g s −1). We compared all 8 oaks using ANCOVA, with litterbed depth as a covariate. The oaks differed for all burning characteristics measured ( P < 0.001). Rank comparisons placed Quercus stellata and Quercus laevis as the species with greatest fire intensity, sustainability, and consumability, equivalent in many measures to longleaf pine and other fire resisters. Quercus virginiana and Quercus hemisphaerica burned with the least intensity, sustainability, and consumability, burning similarly to sand pine and other fire evaders. These results show that oaks common to southeastern United States ecosystems have litter properties, similar to pines, which vary in their ability to sustain fire. Understanding the pyric properties of oak species also suggests that managers prioritize removal of species that hinder prescribed fire effectiveness for restoration of southeastern USA pine–oak ecosystems.

Atmospheric Pressure Plasma Ashing for Display Manufacturing

Due to the various advantages of the use of atmospheric pressure, recent studies on the ashing of organic materials are focused on the atmospheric pressure plasma rather than low pressure plasma. In this study, atmospheric pressure plasma was generated using dielectric covered electrodes and AC pulsed power supply (10 kV) driven at low frequency to remove organic materials on the surfaces of metal such as Cr. In such a configuration, the effects of process conditions and ashing gases on the ashing properties have been investigated. Nitrogen (N2) and oxygen (O2) were used for ignition and ashing, respectively. By adding small amount of O2 to N2, the photoresist ashing rate was increased due to the increment of oxygen radicals in the plasma. However, further addition of oxygen decreased the photoresist ashing rate, possibly because of the lower plasma density caused by the formation of negative ions between oxygen molecules and electrons in the plasma. Additionally, the effect of input voltage on ashing was investigated. The raised input voltage increased the ashing effect possibly due to the increased chemical reaction with organic materials resulting in the increased volatilization and detachment from the surface. In this paper, optimal process condition for gas flow rate and process gap will be discussed.

Mercury Oxidation Promoted by a Selective Catalytic Reduction Catalyst under Simulated Powder River Basin Coal Combustion Conditions

A bench-scale reactor consisting of a natural gas burner and an electrically heated reactor housing a selective catalytic reduction (SCR) catalyst was constructed for studying elemental mercury (Hg0) oxidation under SCR conditions. A low sulfur Powder River Basin (PRB) subbituminous coal combustion fly ash was injected into the entrained-flow reactor along with sulfur dioxide (SO2), nitrogen oxides (NOx), hydrogen chloride (HCl), and trace Hg0. Concentrations of Hg0 and total mercury (Hg) upstream and downstream of the SCR catalyst were measured using a Hg monitor. The effects of HCl concentration, SCR operating temperature, catalyst space velocity, and feed rate of PRB fly ash on Hg0 oxidation were evaluated. It was observed that HCl provides the source of chlorine for Hg0 oxidation under simulated PRB coal-fired SCR conditions. The decrease in Hg mass balance closure across the catalyst with decreasing HCl concentration suggests that transient Hg capture on the SCR catalyst occurred during the short test exposure periods and that the outlet speciation observed may not be representative of steady-state operation at longer exposure times. Increasing the space velocity and operating temperature of the SCR led to less Hg0 oxidized. Introduction of PRB coal fly ash resulted in slightly decreased outlet oxidized mercury (Hg2+) as a percentage of total inlet Hg and correspondingly resulted in an incremental increase in Hg capture. The injection of ammonia (NH3) for NOx reduction by SCR was found to have a strong effect to decrease Hg oxidation. The observations suggest that Hg0 oxidation may occur near the exit region of commercial SCR reactors. Passage of flue gas through SCR systems without NH3 injection, such as during the low-ozone season, may also impact Hg speciation and capture in the flue gas.

Chemical Composition and Ruminal in vitro Degradation of Fresh or Silage of Agave salmiana Otto ex. Salm-Dick

Pinos-Rodríguez, J.M., Gonzalez-Muñoz, S., Badillo, B., García-López, J.C, Aguirre-Rivera, J.R. and Infante, S. 2008. Chemical composition and ruminal in vitro degradation of fresh or silage of Agave salmiana Otto ex. Salm-Dick. J. Appl. Anim. Res., 33: 45–48. Chemical composition and in vitro DM ruminal degradation of whole plant or leaves of Agave salmiana immature, mature or castrated, fresh or silage were estimated. Results suggest that silage process affected pH, DM, NDF, ADF, ash and in vitro DM ruminal degradation, but did not reduce saponin concentration. DM, OM, CP, ADF, ash and DM degradation rate was modified by maturity. Moreover, segment plant impacted OM, CP, ash, saponin and DM degradation rate. Fermentative compounds were found in normal concentrations in the A. salmiana silages.

Direct and residual effects of agro-industrial wastes on a rocket salad ( Eruca sativa Mill.) — Sorghum [ Sorghum bicolor (L.) Moench] sequence

A field study conducted for two years (2002–04) at New Delhi showed that the seed yield (1.80 t ha −1 ) of rocket salad ( Eruca sativa Mill.) obtained by applying 5 t ha −1 pressmud compost based on distillery effluent + half the recommended dose of NPKS (recommended dose: 60 kg N, 13 kg P, 25 kg K and 20 kg S ha −1 ) was on par with the seed yield (1.69 t ha −1 ) recorded with the recommended dose of NPKS. However, the seed yield recorded with the former treatment significantly exceeded that obtained with 5 t ha −1 of a 1:1 mixture of fly ash and distillery effluent + half the recommended dose of NPKS (by 30.4%) or 5 t ha −1 of dry Jatropha curcas leaves + ½ NPKS (by 24.1%). On average, distillery effluent-based pressmud compost + ½ NPKS induced a perceptible increase in the soil-available NPK, recorded after the harvest of rocket salad, compared to the initial fertility status. The uptake of NPKS in the seed and stover of rocket salad was the highest after the application of pressmud compost, closely followed by the recommended dose of NPKS, and the lowest in the control. The residual effect of treatments given to rocket salad was significant on the fodder yield of succeeding sorghum [ Sorghum bicolor (L.) Moench]. The fodder yield recorded with pressmud compost + ½ NPKS was significantly higher than the other treatments. The application of pressmud compost alone was also significantly superior to the same rate of fly ash + effluent mixture or dry Jatropha leaves with respect to the seed yield of rocket salad, residual fertility after the harvest of rocket salad and the fodder yield of succeeding sorghum.

HYDRATION OF CEMENT PASTE AND ESTIMATION OF STRENGTH DEVELOPMENT OF MORTAR USING FLY ASH

The reaction rates of C3S, C2S and fly ash were examined by proposed XRD method to investigate the strength developing mechanism of fly ash concrete. The strength development of fly ash mortar was examined by specimens and estimated with the reaction rates of C3S, C2S and fly ash by proposed method in this paper. The following observations are made: (1) the larger of surface area of cement, the more of hydration degrees; (2) the pozzolanic reaction degree of fly ash correlates with the calcium hydroxide, is approximately in proportion to the account of calcium hydroxide, and influenced by the liquation of calcium hydroxide; (3) when adding fly ash, the hydration of C2S appears to be retarded, though it has little apparently effect on the hydration of C3S.

Evaluation of gas-particle partition of dioxins in flue gas I: Evaluation of gasification behavior of polychlorinated dibenzo- p-dioxins and polychlorinated dibenzofurans in fly ash by thermal treatment

The gasification behavior of polychlorinated dibenzo- p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) in fly ash by thermal treatment has been investigated to estimate gas-particle partition in flue gas. The results obtained in thermal experiments under various conditions showed that gasification of PCDD/Fs depends on air flow rate and treatment weight of fly ash as well as treatment temperature. On the other hand, the results obtained in the thermal experiments using dioxin-free fly ash revealed that during thermal treatment, the de novo synthesis, gasification, and decomposition of PCDFs proceeded at different rates. This difference in the reaction rates indicates that thermal treatment time is also a factor in determining the gas-particle partition of PCDD/Fs in fly ash. Therefore, reasonable thermal treatment conditions were established and applied to three ash samples. For all samples, PCDD/Fs started to gasify at 350 °C treatment, whereas 53–98% of PCDD/F homologs gasified at 400 °C treatment, implying that gaseous PCDD/Fs are dominant in flue gas at temperatures in the range 350–400 °C regardless of particle concentration.

Emissions of NOx and N2O during co-combustion of dried sewage sludge with coal in a circulating fluidized bed combustor

Emissions of NOx and N2O were measured during mono-combustion of dried sewage sludge and co-combustion with coal in a bench-scale circulating fluidized bed combustor (CFBC). The results were compared with previous results obtained using a bubbling fluidized bed combustor (BFBC). The increase in NOx with sludge ash accumulation in the combustor was less for the CFBC than the BFBC, partly because of the higher attrition rate of sludge ash in CFBC resulting from the higher gas velocity. The influence of sludge ash on the formation of NOx in CFBC was less than that in BFBC during sludge combustion. The effects of fuel type on NOx and N2O emissions were also evaluated.

Carbonation rates of concretes containing high volume of pozzolanic materials

The project studies the influence of fly ash and slag replacement on the carbonation rate of the concrete. The experimental work includes samples of pure Portland cement concrete (CEM I 42,5 R), blast-furnace slag concrete (CEM III-B), and fly ash blended concrete. To reveal the effect of curing on carbonation rate, the concretes were exposed to various submerged curing periods during their early ages. After that, the samples were subsequently exposed in the climate room controlling 20 °C and 50% RH until the testing date when the samples had an age of 5 months. Then, the accelerated carbonation test controlling the carbon dioxide concentration of 3% by volume, with 65% relative humidity were started to perform. The depth of carbonation can be observed by spraying a phenolphthalein solution on the fresh broken concrete surface. Finally, according to Fick's law of diffusion theoretical equations are proposed as a guild for estimating the carbonation rate of fly ash and blast-furnace slag concretes exposed under natural conditions from the results from accelerated carbonation tests.

On the photoresist stripping and damage of ultralow k dielectric materials using remote H2- and D2-based discharges

Blanket films of ultralow dielectric constant (ULK) materials and 193nm photoresist films have been processed downstream from hydrogen and deuterium-based discharges produced using an inductively coupled plasma reactor. Photoresist ashing rates and ULK modifications have been determined as a function of process parameters. The explored ULK materials differed widely in porosity and carbon content. The effect of processing time, substrate temperature (200–300°C), and gas composition on the surface and bulk chemical composition of ULK materials was monitored and quantified by ex situ ellipsometry and time-of-flight secondary ion mass spectrometry (SIMS). The stripping rates of 193nm photoresist films were found to strongly depend on processing temperature and only weakly on the nature of the H2/additive gas mixture. The authors found that hydrogen (or deuterium) fully penetrates the high porosity ULK layer, whereas for low porosity materials, such penetration is limited to a 50nm near-surface region. SIMS measurements also reveal that H2 (D2) diffusion into carbon-rich ULK layers can cause substantial carbon depletion throughout the penetration region. ULK damage values increase with temperature and injection of gas additives such as argon, helium, and nitrogen to H2 or D2 process gases. For each ULK material, the amount of damage depends on the gas mixing ratio; in general, high percentages of nitrogen in H2∕N2 (or D2∕N2) mixtures cause the most damage. Overall, the results demonstrate that ULK ashing damage depends strongly on both ULK material properties and H2-based plasma process parameters. In addition, the authors observed in this work a kinetic isotope effect for stripping of 193nm photoresist films in H2∕D2∕N2-based discharges. For given ashing process conditions, the photoresist ashing rate decreases by a factor of 1.414 (or square root of 2) in D2 plasma compared to H2 plasma. This can be explained by the influence of the H or D mass on the chemical reaction rate through a change in the frequency of nuclear vibrations of the reacting atoms. The presence of the kinetic isotope effect for gas mixtures provides unambiguous evidence of the rate-limiting role of atomic hydrogen in the fundamental etching reaction. Simultaneously processed ULK materials showed minor film thickness changes (&amp;lt;10nm) in H2 or D2 discharges, and the ULK damage level does not reflect a kinetic isotope effect. Therefore the H∕D isotope effect can be used to separate H2∕D2 associated ashing and etching processes from other chemistries or mechanisms.

Effects of different rates of fly ash and sewage sludge mixture amendments on cation availability and their leachability

A leaching column study was conducted to evaluate the leaching of cations from soils amended with a mixture of (1:1) fly ash (FA) from Port Wentworth power plant, Savannah, GA: sewage sludge (SS) from President Street water pollution control plant, Savannah, GA. Two sets of soil-leaching columns (30-cm high and 7.5-cm diameter; 15 columns per soil) were prepared with a fine sandy soil from Florida (Candler fine sand; pH 6.8) and Georgia (Ogeechee loamy sand; pH 5.6). The top one inch of soil from each of these columns was amended (3 columns per treatment) with 1:1 mixture of SS and FA at either 0, 24.7, 49.4, 98.8 or 148.3 Mg ha− 1 rate. After saturating the columns with deionized water, 18 cycles of intermittent leaching and drying was performed on weekly basis. Leaching of major cations and changes in ionic strength and pH were evaluated on half pore volume (220 mL) of leachate collected at each event. Results of this study indicated that leaching of cations increased rapidly up to the 3rd leaching event, and then rapidly decreased and the concentration of cations reached somewhat similar to that of unamended soil columns. Effects of soil type and rates of amendments on leaching of major cations along with changes of pH and ionic strength are discussed in this paper.

Influence of quicklime addition on the mechanical properties and hydration degree of blended cements containing different fly ashes

Even though the use of pozzolanic and latent hydraulic materials (such as fly ash, slag and natural pozzolans) in the construction sector is nowadays a common practice, certain deficits associated with these materials have initiated research that aims to reduce the negative effects that they introduce into cementitious systems. With respect to fly ash, its relatively slow pozzolanic reactivity hinders its greater utilization; hence cost efficient methods of activation are on demand. In this work, cement systems containing the two typical types of Hellenic fly ashes (of high and moderate calcium content) were chemically activated by adding industrially produced quicklime. A first step in assessing the efficiency of the above procedure was based in monitoring the compressive strength development, lime depletion values and data derived from a selective dissolution procedure (based on a mixture of picric acid–methanol). Moreover, evolution of the fly ash reaction and the morphology of the formed hydration products were examined by means of scanning electron microscopy. Evidence included in this investigation reveal that quicklime presence accelerated the reaction rate of high-calcium fly ash, whereas in the case of lower-calcium fly ash, quicklime had a positive impact only during the very early stages of hydration and thereafter acted inhibitory with respect to its reactivity development.