Preparation and Characterization of Polyurethane Waterproof Coatings Containing Fly Ash
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Polyurethane waterproof (PW) coatings are increasingly demanded in Korea for repairing cracks on old building roofs and construction of many sporting facilities. Calcium carbonate, a common filler, is incorporated in PW compositions. In this study, PW coatings were prepared by substituting a part of calcium carbonate with fly ash. The maximum amounts of calcium carbonate which can be substituted by fly ash obtained in the cyclone and bag filter dust collectors were 20 and 10%, respectively. It was found that the curing rate of PWs ran be controlled by varying the amount of Pb-octoate catalyst. The elongations at break as well as tensile strength and tear strength of PW coatings containing fly ash could also be adjusted such that their values were comparable to those of a standard PW coating by varying relative amounts of some components. However, the amount of cadmium, mercury, and lead leached from PW coatings containing fly ash obtained from the bag filter collector exceeded the respective allowed upper limits, mainly due to the initial high contents of them in the fly ash. On the other hand, PW coatings containing fly ash obtained from the cyclone collector exhibited better mechanical properties and did not release any significant amounts of the heavy metals. Thus, it was concluded that PW coatings containing fly ash can be utilized for practical applications as long as an appropriate fly ash is used.Keywords:
High calcium
Filler (materials)
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Fly ash as one of industrial solid wastes in coal fired power plant causes more and more serious ecological problem and environmental pollution. Cement-based fly ash waterproof coating with good water proof effect,high volume and high value-added was prepared by surface modification and chemical activation with low calcium fly ash of Panzhihua Power Plant. Influence of factors including modification,chemical activation of fly ash and simultaneous action of modification and chemical activation on performance of coating products were investigated. Effect of sulfate and silicate generating system on the performance of coating was also studied. Activation effect of fly ash was analyzed by micro-XRD and SEM. Results showed that fly ash could improve coating workability by surface modification,with impermeability stress increased by 67% compared with that of raw ash,and increased by 25% compared with that of chemical activation. Permeability ability of fly ash by both surface modification and chemical activation was significantly improved by increasing of 127% correspondingly compared with that of raw fly ash. Activation effect of sulfate generating system was better than those of silicate generating system,with impermeability stress of 15d and chemical activation higher than those of 28d standard in GB18445-2001.
Calcium silicate hydrate
Calcium silicate
Surface Modification
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Fly ash particles are easy to agglomerate and have poor dispersivity because of the physical and chemical adsorption occurred on the surface during collecting and storing.When used as reinforcing phase,dispersion property of fly ash directly influenced the properties of composite material.This paper begins with H2SO4 acid-dissolution method for surface treatment of fly ash,and through the powder metallurgy,the modified fly ash/aluminum composite material was prepared.With the fly ash particles content increasing,the density of composite materials gradually decreased,and the hardness first increased and then decreased,the density and hardness increased with the molding temperature increasing.SEM,XRD analysis shows that the fly ash treated by sulfuric acid,the surface polarity is reduced and the dispersion of fly ash particles and the activity of fly ash are improved and sulfuric acid only dissolves the glass phase,while the crystal phase is insoluble in sulfuric acid.Under the molding temperature of 650 ℃,and the fly ash disperses uniformly in the matrix,and both hardness and density are high,therefore the molding temperature of 650 ℃ is optimum.But defects and a small amount of pores still exist in composite materials.
Agglomerate
Molding (decorative)
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A process for treating fly ash to render it highly usable as a concrete additive. A quantity of fly ash is obtained that contains carbon and which is considered unusable fly ash for concrete based upon foam index testing. The fly ash is mixed with a quantity of spray dryer ash (SDA) and water to initiate a geopolymerization reaction and form a geopolymerized fly ash. The geopolymerized fly ash is granulated. The geopolymerized fly ash is considered usable fly ash for concrete according to foam index testing. The geopolymerized fly ash may have a foam index less than 40%, and in some cases less than 20%, of the foam index of the untreated fly ash. An optional alkaline activator may be mixed with the fly ash and SDA to facilitate the geopolymerization reaction. The alkaline activator may contain an alkali metal hydroxide, carbonate, silicate, aluminate, or mixtures thereof.
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In order to improve the whiteness of fly ash, the particles were coated by in-situ precipitation of calcium carbonate. After different mass ratios of calcium oxide to fly ash were mixed into water, a certain amount of carbon dioxide was bubbled into the mixture to form a precipitated calcium carbonate deposit on the surface of fly ash. With the help of scanning electron microscopy (SEM), the process and the coating mechanism of the unmodified and modified fly ash were studied. The results showed that when a 1:1 mass ratio of calcium oxide to fly ash was implemented, the whiteness of fly ash was increased from 30.3 (the original fly ash) to 74.0 (the modified fly ash). After appropriately controlling for the rate of carbon dioxide, the whiteness was improved to meet the standard for filler in the papermaking industry, and also great advantages in paper physical strength were demonstrated.
Filler (materials)
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Low calcium fly ash of Panzhihua power plant was applied as raw material to prepare cement-based waterp roof coating.Impacts of the surface modification and chemical activation of fly ash on the performance of coating and activation effect of different activator were compared.At the same time,the experiment has conducted micro-XRD,SEM ana lysis for the activation mechanism.The results show that:after fly ash surface modification,the impermeable pressure of coating has increased 67% more than th at of coating with original ash,25% more than that of coating with fly ash activated by chemical activator.After both surface modification and chemical activation for fly ash,the impermeable pressure of the coating has significantly improved.The 15d compressive strength,flexural strength,impermeable pressure,as well as the impermeable pressure ratio of coatings with fly ash activated by both surface modification and chemical activation are higher than those of the GB 18 445—2001 standard 28d value.
Surface Modification
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Fly ash with fine particle size and high hardness can be used to prepare PVC composites with perfect mechanical properties and low cost.With the aim of producing PVC composite with high filling of fly ash,the surface modification of fly ash and the influence of the plasticizeron on the rheological behavior of composite were investigated.PVC composite with high filling of fly ash and perfect mechanical properties was fabricated by use of the plasticizer(DIOP,diisooctyl phthalate) and the modifiers(silane and stearic acid) owing to the improvement of the dispersion and compatibility of fly ash in PVC.PVC-fly ash composite with a bending strength of 29.1 MPa was produced at the optimized condition(mass ratio):fly ash:PVC:DIOP:stearic acid:silane were 300:100:25:1.5:1.5.
Stearic acid
Plasticizer
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Different agents were used to control the crystalline morphology of calcium carbonate on the surface of fly ash, which was then used as a papermaking filler in an attempt to improve the utilization rate of fly ash and reduce the dust pollution problem. A mixed solution of calcium hydroxide and fly ash was used as the raw materials, and then three crystal form control agents were tested: (NaPO3)6, ZnCl2, and Na2B4O7·10H2O. A certain amount of carbon dioxide was bubbled into the mixture to form a precipitated calcium carbonate deposit on the surface of fly ash. The calcium carbonate on the fly ash surface was altered by changing the amount of crystal form control agent to determine the best coating effect. The results showed that at the 0.35% ZnCl2 dosage (relative to the theoretical quantity of the calcium carbonate), the surface of the fly ash was uniformly coated with a layer of spherical calcium carbonate crystals and there was a good coating effect. The highest fly ash brightness obtained was 65.3% ISO, and when this fly ash was used as a paper filler, the paper brightness was 75.6% ISO. More importantly, this study demonstrated the potential of fly ash in papermaking.
Papermaking
Filler (materials)
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The hardening mechanism, optimum mixture, curing condition and environmental safety of a paste composed of a fly ash and alkali was investigated. As a result, it was found that a fraction of fly ash reacted with water glass and formed amorphous or low ordered crystalline compounds of the type of . The optimal mixing proportion of coal ash(fly ash, bottom ash) solid was cement 5%, water glass 15%, NaOH 10%, 5% and curing method was air curing after moist curing during 24 hours in 5. Coal ash(fly ash, bottom ash) solid can be achieved compressive strength of 34.9MPa, at 7-days. A heavy metals quantity satisfied regulation value. The use of coal ash(fly ash, bottom ash) helps in reducing environmental pollution, solving some of the coal ash(fly ash, bottom ash) waste problems.
Incinerator bottom ash
Hardening (computing)
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Fly ash, a waste product from thermal power plants, is one of the good alternatives for use as a filler in polymers, especially in flame retardants. Fly ash is an environmentally friendly fire retardant additive for composites, used in place of conventional flame retardant additives such as halogenated organic compounds, thus promoting environmental safety. In this study, fly ash was modified with stearic acid to improve adhesion at the polymers interface and increase compatibility. Fly ash was studied at various volumes (5, 10, and 20 wt.% fly ash) used in this study to synthesize fly ash-epoxy composites. The results show that the tensile strength, flexural strength, compressive strength, and impact strength of these synthetic materials increase when fly ash is modified to the surface, compressive strength: 197.87 MPa, flexural strength: 75.20 MPa, impact resistance: 5.77 KJ/m 2 , and tensile strength: 47.89 MPa. Especially, the fire retardant properties are improved at a high level, with a modified 20% fly ash content: the burning rate of 16.78 mm/min, minimum oxygen index of 23.2%, and meet the fire protection standard according to UL 94HB with a burning rate of 8.09 mm/min. Scanning electron microscopy (SEM) and infrared spectroscopy were used to analyze the morphological structure of fly ash after being modified and chemically bonded with epoxy resin background.
Stearic acid
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In order to explore the comprehensive disposal and use of two kinds of solid waste-fly ash and desulphogypsum, in power plant, the ratios of fly ash/desulphogypsum and water/solid between fly ash and desulphogypsum, with respect to the two major solid wastes in coal-fired power plants, are studied by experiments, while they are being naturally cured in the air and the influences of chemical additives such as sulfates, lime, NaOH and acid exciting agents on cementitious material strength are analyzed. The results indicate that the optimum reaction mass ratio between fly ash and desulphogypsum is 3∶2; the compressive strength of corresponding cementitious material is the highest with 1% K2SO4, 1% lime, 3% NaOH, 10% HCl solution being, respectively, added into fly ash-desulphogypsum system. And when the ratio of water/solid is 0.23, the compressive strength is the best.
Cementitious
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