Pozzolanic reaction of fly ash modified by fluidized bed reactor-vapor deposition

This study aimed to introduce fluidized bed reactor-vapor deposition (FBR-VD) into the modification of fly ash (FA) using the activators of NaOH, Na2SO4, and NaCl. The compressive strength, non-evaporable water and the hydration degree fly ash (HDFA) were investigated. The scanning electron microscopy (SEM), and the X-ray powder diffraction (XRD) Rietveld analysis were also conducted. The results demonstrate that FBR-VD can benefit the compressive strength when the dosage rates of NaOH, Na2SO4 and NaCl are 0.1%, 0.5%, and 0.5%, respectively. The non-evaporable water and HDFA also increased at certain activator dosage rates. A modification layer consisting of nanometer-scale crystals forms on the surface of the FA beads, with NaOH or Na2SO4 applied. NaOH can react with FA and promote its pozzolanic activity. Na2SO4 and NaCl can benefit the HDFA by remaining undissolved, to increase their concentration around FA. The enhanced HDFA is also proved by the consumption of Ca(OH)2.

[1]  S. Donatello,et al.  Very High Volume Fly Ash Cements. Early Age Hydration Study Using Na2SO4 as an Activator , 2013 .

[2]  A. Öztas,et al.  Appraisal of long-term effects of fly ash and silica fume on compressive strength of concrete by neural networks , 2007 .

[3]  H. Brouwers,et al.  Characterization of alkali activated slag–fly ash blends containing nano-silica , 2015 .

[4]  S. Martínez-Ramírez,et al.  Microstructure studies on Portland cement pastes obtained in highly alkaline environments , 2001 .

[5]  C. Lee,et al.  Strength and microstructural characteristics of chemically activated fly ash–cement systems , 2003 .

[6]  Prinya Chindaprasirt,et al.  Influence of NaOH solution on the synthesis of fly ash geopolymer , 2009 .

[7]  Xiao-Yong Wang.  Effect of fly ash on properties evolution of cement based materials , 2014 .

[8]  Reinhard Trettin,et al.  The Influence of Different Drying Methods on Cement Paste Microstructures as Reflected by Gas Adsorption: Comparison between Freeze-Drying (F-Drying), D-Drying, P-Drying and Oven-Drying Methods , 2006 .

[9]  M. Hornbostel,et al.  Coatings for corrosion protection of porous substrates in gasifier components , 2008 .

[10]  Jueshi Qian,et al.  Activation of blended cements containing fly ash , 2001 .

[11]  João Castro-Gomes,et al.  Strength development of alkali-activated fly ash produced with combined NaOH and Ca(OH)2 activators , 2014 .

[12]  S. Srinivasan,et al.  INFLUENCE OF ACTIVATED FLY ASH ON CORROSION-RESISTANCE AND STRENGTH OF CONCRETE , 2003 .

[13]  Kefei Li,et al.  Determination of cement hydration and pozzolanic reaction extents for fly-ash cement pastes , 2012 .

[14]  Hongbo Guo,et al.  Microstructure and mechanical properties of yttria stabilized zirconia coatings prepared by plasma spray physical vapor deposition , 2015 .

[15]  Chai Jaturapitakkul,et al.  Effect of fly ash fineness on compressive strength and pore size of blended cement paste , 2005 .

[16]  A. Xu,et al.  Effect of fly ash on the microstructure of cement mortar , 1993 .

[17]  Neil B. Milestone,et al.  Hydration and properties of sodium sulfate activated slag , 2013 .

[18]  P. Basheer,et al.  Chemical and Mechanical Stability of Sodium Sulfate Activated Slag after Exposure to Elevated Temperature , 2012 .

[19]  G. Renaudin,et al.  Structural transition of Friedel's salt 3CaO·Al2O3·CaCl2·10H2O studied by synchrotron powder diffraction , 2002 .

[20]  Hashim Abdul Razak,et al.  Comparison of different methods for activation of ordinary Portland cement-slag mortars , 2011 .

[21]  Barbara Lothenbach,et al.  Quantification of the degree of reaction of fly ash , 2010 .

[22]  Caijun Shi,et al.  Pozzolanic reaction in the presence of chemical activators: Part II — Reaction products and mechanism , 2000 .

[23]  Aiping Chen,et al.  In situ synthesis of CNTs/Fe–Ni/TiO2 nanocomposite by fluidized bed chemical vapor deposition and the synergistic effect in photocatalysis , 2014 .

[24]  S. Delvasto,et al.  Comparative and semi-quantitative XRD analysis of Friedel’s salt originating from pozzolan and Portland cement , 2011 .

[25]  M. Ahmaruzzaman,et al.  A review on the utilization of fly ash , 2010 .

[26]  Xianhua Wei,et al.  Investigation of low and mild temperature for synthesis of high quality carbon nanotubes by chemical vapor deposition , 2014 .

[27]  A. Barron,et al.  Control over Cement Setting Through the Use of Chemically Modified Fly Ash , 2006 .

[28]  Aleksandar Jovović,et al.  The influence of variable operating conditions on the design and exploitation of fly ash pneumatic transport systems in thermal power plants , 2008 .

[29]  S. Antiohos,et al.  Influence of quicklime addition on the mechanical properties and hydration degree of blended cements containing different fly ashes , 2008 .

[30]  Meenu Kalra,et al.  Hydration of ternary cementitious system: Portland cement, fly ash and silica fume , 2014, Journal of Thermal Analysis and Calorimetry.

[31]  J. Marchand,et al.  INFLUENCE OF CURING TEMPERATURE ON CEMENT HYDRATION AND MECHANICAL STRENGTH DEVELOPMENT OF FLY ASH MORTARS , 1997 .

[32]  Neil B. Manson,et al.  Perfect alignment and preferential orientation of nitrogen-vacancy centers during chemical vapor deposition diamond growth on (111) surfaces , 2014, 1401.4106.

[33]  P. Dubruel,et al.  The influence of different drying techniques on the water sorption properties of cement-based materials , 2014 .

[34]  S. Martínez-Ramírez,et al.  OPC hydration with highly alkaline solutions , 2001 .

[35]  C. Poon,et al.  Activation of fly ash/cement systems using calcium sulfate anhydrite (CaSO4) , 2001 .

[36]  A. Xu,et al.  Microstructural Development in High‐Volume Fly‐Ash Cement System , 1994 .

[37]  Brigitte Caussat,et al.  Chemical vapor deposition of silicon nanodots on TiO2 submicronic powders in vibrated fluidized bed , 2010 .

[38]  Pei-ming Wang,et al.  Influence of particle size distribution on accurate X-ray quantitative analysis of tetracalcium aluminoferrite , 2015 .

[39]  Shaswat Kumar Das,et al.  The Effect of Basic Oxygen Furnace Slag and Fly Ash Additions in Triaxial Porcelain Composition: Phase and Micro Structural Evolution , 2013, Transactions of the Indian Institute of Metals.

[40]  E. Peris Mora,et al.  Influence of different sized fractions of a fly ash on workability of mortars , 1993 .

[41]  C. Shi,et al.  Pozzolanic reaction in the presence of chemical activators. Part I. Reaction kinetics , 2000 .

[42]  C. Poon,et al.  Degree of hydration and gel/space ratio of high-volume fly ash/cement systems , 2000 .

[43]  F. Pruckner,et al.  Effect of CaCl2 and NaCl additions on concrete corrosivity , 2004 .

[44]  D. Neumann,et al.  Effect of NaOH on the kinetics of tricalcium silicate hydration: A quasielastic neutron scattering study , 2006 .

[45]  J. Bijen,et al.  The reaction of fly ash in concrete a critical examination , 1989 .

[46]  W. Yao,et al.  Quantitative evaluation of hydrated cement modified by silica fume using QXRD, 27Al MAS NMR, TG–DSC and selective dissolution techniques , 2012 .

[47]  M. S. Jaafar,et al.  The effect of various chemical activators on pozzolanic reactivity: A review , 2012 .

[48]  Min-Hong Zhang,et al.  HYDRATION IN HIGH-VOLUME FLY ASH CONCRETE BINDERS , 1994 .

[49]  P. Chindaprasirt,et al.  Effect of SiO2 and Al2O3 on the setting and hardening of high calcium fly ash-based geopolymer systems , 2012, Journal of Materials Science.

[50]  A. Neville.  Properties of Concrete , 1968 .

[51]  P. Brown,et al.  The formation of calcium sulfoaluminate hydrate compounds: Part II , 1999 .

[52]  X. Querol,et al.  Quantitative Rietveld analysis of the crystalline and amorphous phases in coal fly ashes , 2013 .

[53]  B. Pacewska,et al.  Investigations of cement early hydration in the presence of chemically activated fly ash , 2008 .

[54]  Shizong Long,et al.  ESCA study on the early C3S hydration in NaOH solution and pure water , 1998 .

[55]  V. Sirivivatnanon,et al.  Influence of fly ash fineness on strength, drying shrinkage and sulfate resistance of blended cement mortar , 2004 .