Effect of MSWI Fly Ash and Incineration Residues on Cement Performances

The activities of municipal solid waste incineration (MSWI) fly ash and incineration residues were studied contrastively, through the component analysis and the activity ratio tests. The mechanical properties, hydration mechanism and leaching toxicity of the hardened cement paste mixing with MSWI fly ash and incineration residues were investigated. The experimental results indicated that the active constituents (CaO+Al2O3+Fe2O3) in MSWI fly ash were higher than those in incineration residues. Therefore the ...     

The Cement Solidification of Municipal Solid Waste Incineration Fly Ash

The chemical composition, the content and the leachability of heavy metals in municipal solid waste incineration （ MSWI） fly ash were tested and analyzed. It is shown that the leachability of Pb and Cr exceeds the leaching toxicity standard, and so the MSWI fly ash is considered as hazardous waste and must be solidifled. The effect of solidifying the MSWI fly ash by cement was studied, and it is indicated that the heavy metals can be well immobilized if the mass fraction of the fly ash is appropriate. The heavy metals were immobilized within cement hydration products through either physical fixation, substhtaion, deposition or adsorption mechanisms.     

混合材对MSWI制CSA水泥性能的影响

以城市垃圾焚烧飞灰（MSWI）为主要原料,在实验室成功烧制了硫铝酸钙（CSA）水泥熟料.研究了单掺或复掺不同种类、不同掺量的混合材后,CSA水泥的力学性能和水化性能.结果表明：石灰石粉（LI）/矿渣粉（SL）在CSA水泥中较为适用,而粉煤灰（FA）/MSWI的活性较差;单掺4种混合材均对CSA水泥早期强度产生不利影响;单掺LI/SL对后期强度发展有益;复掺混合材较单掺效果好,尤其是试样10％LI＋10％SL、10％LI＋10％MSWI和5％LI＋15 ％SL.     

Microstructures and thermal properties of municipal solid waste incineration fly ash

To analyze the feasibility of utilization of thermal technology in fly ash treatment, thermal properties and microstructures of municipal solid waste incineration (MSWI) fly ash were studied by measuring the chemical element composition, specific surface area, pore sizes, functional groups, TEM image, mineralogy and DSC-TG curves of raw and sintered fly ash specimens. The results show that MSWI fly ash particles mostly have irregular shapes and non-typical pore structure, and the supersonic treatment improves the pore structure; MSWI fly ash consists of such crystals as SiO₂, CaSO₄ and silica-aluminates, and some soluble salts like KCl and NaCl. During the sintering process, mineralogy changes largely and novel solid solutions are produced gradually with the rise of temperature. Therefore, the utilization of a proper thermal technology not only destructs those persistent organic toxicants but also stabilizes hazardous heavy metals in MSWI fly ash.     

Solidification of Municipal Solid Waste Incineration Fly Ash with Cement and Its Leaching Behaviors of Heavy Metals

The solidifying qffect of cement addition on municipal solid waste incineration fly ash ( MSWFA for short, collected from the gas exhaust system of MSW incinerator), the interaction of MSWFA with cement and water and the leaching of heavy metals from cement-solidified MSWFA are investigated. The main results show that : ( 1 ) when MSWFA is mixed with cement and water, 112 evolution, the formation and volume expansion of AFt will take place, the volume expansion can be reduced by ground rice husk ash addition ; (2) heavy metals do leach from cement-solidified MSWFA and at lower pH more leaching will occur; (3) compared with cement - so-lidified fly ash, the leachate of solidified MSWFA is with higher heavy metal contents ; (4) with the increment of cement addition leached heavy metals are decreased ; and (5) concentrations of Zn , Mn , Cu and Cd in all the leachates can meet the relevant Standards of Japan, but as the regulations for soil and groundwater protection of Japan are concerned, precautions against the leaching of Pb , Cl^- and Cr^6 and so on are needed.     

焚烧飞灰熔融特性与熔渣利用技术研究进展

垃圾焚烧飞灰中含有高浸出浓度的Pb,Cd,Cu,Zn等重金属,属于危险废物。高温熔融技术可以有效地控制焚烧飞灰中的重金属污染物。从飞灰无害化和资源化2个角度介绍了熔融技术的研究进展,分析了熔融技术的优缺点,在综述国内外研究成果的基础上,为今后焚烧飞灰的热处理技术提出了研究方向。     

利用垃圾焚烧飞灰固化污染底泥的实验研究

为探讨利用垃圾焚烧飞灰代替水泥进行污染底泥固化的可行性,研究了不同配比的底泥、水泥、垃圾焚烧飞灰的固化体抗压强度及浸出毒性.结果表明：固化剂中用20%的垃圾焚烧飞灰替代10%的水泥配置的固化体7.d,其抗压强度可达0.24.MPa,重金属浸出浓度低于毒性标准,固化体可进入固废填埋场填埋处置.     

MSWI fly ash based novel solidification/stabilization matrices for heavy metals

The possibilities of MSWI fly ash as a major constituent of novel solidification/stabilization matrices for secure landfill were investigated by mixing MSWI fly ash with rich aluminum components, which was added as bauxite cement or metakaolinite instead, to form Friedel and Ettringite phases with high fixing capacities for heavy metals. The physical properties, heavy metals-fixing capacity, mineral phases and its vibration bands in the novel matrices were characterized by compressive strength, TCLP（toxic characteristic leaching procedure）, XRD （x-ray diffraction） , DTG （derivative thermogravimetry）, and FTIR （fourier transform infrared spectroscopy）, respectively. The Tessier＇s five-step sequential extraction procedure was used to analyze the fractions of chemical speciation for Pb, Cd and Zn ions. The experimental results indicate that Friedel-Ettringite based novel solidification/stabilization matrices can incorporate Pb, Cd and Zn ions effectively by physical encapsulation and chemical fixation, and it exhibits a great potential in co-landfill treatment of MSWI fly ash with some heavy metals-bearing hazardous wastes.     

Effect of Fly Ash on Rheological Properties of Cement Paste

This paper is aimed to study the factors influencing rheological properties of cement paste with fly ash,including the quantity of cement replaced by fly ash,types of the fly ash,degree of cement hydration and the microstructure of cement paste. By changing the water-cement ratio,mixing different amounts of fly ash,adding different types fly ash,the rheological parameters of cement paste are measured with a rheometer,and the needle penetration are tested by Vical needle. A ultrasound velocity test was aslo employed to monitor hydration of paste at early ages. Combinations of different factors on the rheological properties of cement paste are studied. The objective is to reveal the effect mechanism of material nature and proportion of each component on the rheological properties of cement paste with fly ash.     

Hydration Kinetics of Municipal Solid Wastes Incineration(MSWI) Fly Ash-Cement

Hydration heat behavior and kinetics of blended cement containing up to 20% MSWI fly ash were investigated based on its hydration heat evolution rate measured by isothermal calorimeter. Kinetics parameters, N and K, and hydration degree, Ca(OH)_2 content, were also calculated and analyzed. According to the experimental results, the induction period was elongated, the second heat evolution peak was in advance, and the third hydration heat peak could be detected due to MSWI fly ash pozzolanic reaction. The hydration reaction rate was controlled by nucleation kinetics in the acceleration period and then by diffusion in the decay period, but in the deceleration period, the hydration experienced a dual controlling reaction of autocatalytic chemical reaction and diffusion. The hydration rate of blended cement was faster. Ca(OH)_2 content increased before 14 days.     

Utilization of municipal solid waste incineration fly ash in lightweight aggregates

Washing pre-treatment of municipal solid waste incineration (MSWI) fly ash blended with shale and sludge was utilized in the manufacture of light-weight aggregates and processed to form ceramic pellets. A formula uniform design was performed to arrange the mixture ratio of the materials. The optimal mixture ratio of the materials was determined by measuring the bulk density, granule strength, and 1 h water absorption of the pellets. It is shown that the optimal mixture ratios of materials, MSWI fly ash, shale, and sludge, are 23.16%, 62.58%, and 14.25% (mass fraction), respectively. The performance testing indicators of light-weight aggregates are obtained under the optimum mixture ratio: bulk density of 613 kg/m³, granule strength of 821N, and 1 h water absorption of 11.6%, meeting 700 grade light-aggregate of GB/T 17431.2—1998 standard. The results suggest that utilization of MSWI fly ash in light-weight aggregates is an effective method and a potential means to create much more values.     

Properties and mechanism of CFBC fly ash-cement based stabilizers for lake sludge

Circulating fluidized bed combustion(CFBC) fly ash was mixed with cement or lime at a different ratio as a stabilizer to stabilize lake sludge.In order to understand the influences of stabilizers on the lake sludge properties,tests unconfined compressive strength,water stability and SEM observation were performed.The experimental results show that with the increase of the curing time,the strength of all the stabilized specimens increase,especially the samples containing cement.The strength of the specimens is decreased with the increasing of the CFBC fly ash/cement ratio,the optimum ratio between CFBC fly ash and cement is 2:3.The water stability of CFBC fly ash-cement based stabilizers is higher than those of cement and lime.Moreover,the lake sludge stabilization mechanism of CFBC fly ash-cement based stabilizers includes gelation and filling of the hydration products,i e,C-S-H gel and the AFt crystal,which act as benders to solidify those particles together and fill in the packing void of the aggregates.     

Glass-ceramics made from arc-melting slag of waste incineration fly ash

Grate fly ash and fluidized bed fly ash mixed with glass cullet additive respectively were melted in the electronic arc-furnace. The product, arc-melting slag, was further treated by crushing, pressing and heat treatment in order to make the glass-ceramics. The crystallization behaviors of the produced glass-ceramics were examined by differential thermal analysis (DTA), X-ray diffractometry (XRD) and scanning electron microscopy (SEM). Results show that main crystalline phase of the glass-ceramics from grate fly ash is wollastonite (CaSiO₃) with small amount of diopside (Ca(Mg,Al)(Si,Al)₂O₆), and that from fluidized bed fly ash is diopside (Ca(Mg,Al)(Si,Al)₂O₆). It is found that the glass-ceramics sintered at 850 °C and 1 000 °C from grate fly ash and fluidized bed fly ash respectively have the optimal physical, mechanical and chemical characteristics. Glass-ceramics samples, produced from incinerator fly ash with desirable properties and the low leaching concentration of heavy metals, can be the substitute of nature materials such as marble, granite and porcelain tiles.     

低水胶比下工业废渣与水泥熟料的相互作用

探索了工业废渣与水泥熟料相互作用的定量指标.以掺惰性材料———刚玉粉的水泥水化样作参比样,研究和分析了低水胶比下粉煤灰、煤矸石与水泥熟料的相互作用.实验中粉煤灰掺量为10%~80%,煤矸石掺量为20%~60%,龄期为1~672 h.结果表明,水泥中掺入粉煤灰和煤矸石,由于水泥熟料用量降低而产生的稀释作用促进了水泥熟料的水化,而其他物理化学作用则依工业废渣的掺量、水化样龄期的不同而表现为促进或延缓水泥熟料的水化.     

低水胶比下粉煤灰对水泥早期水化的影响

提出可用等效结合水含量和水化影响因子来定性和定量分析粉煤灰对水泥早期水化作用的大小。若粉煤灰的水化影响因子 >1,则粉煤灰促进水泥水化 ,值越大 ,促进作用越显著 ;若粉煤灰的水化影响因子 <1,则粉煤灰延缓水泥水化 ,值越小 ,延缓作用越显著。同时研究和分析了低水胶比下粉煤灰不同品种和掺量对水泥早期水化的影响     

纳米SiO2超高强高流态混凝土及改性机理

通过正交试验提出纳米超高强高流态混凝土的胶凝材料配合比设计参数,并研究了纳米SiO₂的掺入对传统掺硅灰、粉煤灰超高强水泥基胶凝材料强度及工作性能的影响。在保证水胶比不变的条件下,开展了混凝土配合比试验,并研究了纳米SiO₂对混凝土抗压强度的影响及其微观机理。结果表明：超高强高流态混凝土中胶凝材料最优比例为：纳米SiO₂：硅灰：粉煤灰：水泥=1：8：20：71;在胶凝材料用量为600~1 000 kg/m³范围内,随着其掺量的增加,混凝土流动度不断增加,抗压强度先增大后减小,当其掺量为800 kg/m³时,抗压强度最大。分析认为,纳米SiO₂、硅灰与粉煤灰形成的三元多尺度堆积体系能优化粉体材料在混凝土中的微集料密实填充效应,纳米SiO₂的二次水化反应也有效改善了硬化水泥石的微观结构,并优化其形态分布,进一步增大其强度。     

Early age properties of cementitious materials by electrical resistivity measurement

Three cement pastes were prepared with the fixed water-binder ratio and different fly ash contents. The compression test and electrical resistivity measurement of the paste mixes were conducted during 48 h. The changes of the CH content and the non-evaporable water content in the cement-fly ash hydration systems with time were obtained by the thermal gravimetric analysis. The experimental results show that dilution effect of fly ash as micro-filler is dominant mechanism before 48 h, which appears to decrease in the CH content and the non-evaporable water content, also in compressive strength and electrical resistivity, with the increase of fly ash replacement. The relationships between CH content, non-evaporable water content and electrical resistivity show that electrical resistivity can be the indicators of hydration products CH and non-evaporable water. The correlation of the compressive strength f _c and the electrical resistivity ρ can be obtained as f _c =8.3429 ρ = 6.7088 for the period of 48 h. The early age compressive strength can then be predicted by electrical resistivity measurement.     

Influence of ultra-fine fly ash on hydration shrinkage of cement paste

1INTRODUCTION Hydrationshrinkageisalsoknownaschemicalshrinkage[1].Thesolidvolumeincreasesafterce menthydrating,buttheabsolutevolumeofcementwatersystemreduces.Usuallythetotalamountofvolumeshrinkageofcementwatersystemis7%9%[1,2].Withthedevelopmentofthetechno logyofcementandconcrete,concretewithhighstrengthandhighperformanceisthedevelopingtendencynow.However,nowadays,comparedwithordinaryconcrete,thehydrationshrinkageofhighperformancecementconcreteincreasesobvi ouslybecauseoftheaccelerationof…     

Effect of limestone powder and fly ash on magnesium sulfate resistance of mortar

The effect of limestone powder and fly ash on magnesium sulfate resistance of mortar was studied by testing on the strength, expansion and hydration products of the specimens stored in MgSO₄ solution at certain periods. The experimental results show that the strength of mortar stored in MgSO₄ solution increases a little before 28 d, but decreases fast subsequently. The more the contents of limestone powder and fly ash, the less the strength losses. Mortar swells in the MgSO₄ solution with the soaking time. And the more the contents of limestone powder and fly ash, the less the expansion rate is. The expansion or strength loss of mortars results from the expansion of gypsum, as well as the loss of Ca(OH)₂ and other hydration products of cement. The magnesium sulfate resistance of the mortars containing limestone powder and fly ash is high.     

水泥复合土的压缩模量试验

为了改善水泥复合土的力学特性,在水泥复合土形成时添加了膨润土和粉煤灰,设计了水泥复合土的配合比;采取正交试验方法,进行了水泥复合土的压缩模量试验;利用极差分析和方差分析的方法研究了水泥掺量、膨润土掺量和粉煤灰掺量对水泥复合土压缩模量的影响.结果表明:随着水泥掺量的增加,水泥复合土的压缩模量逐步增大,而随着膨润土掺量和粉煤灰掺量的增加,水泥复合土的压缩模量均逐渐降低.水泥掺量对水泥复合土压缩模量的影响最大,膨润土掺量的影响次之,粉煤灰掺量的影响偏小.