The Experts below are selected from a list of 321 Experts worldwide ranked by ideXlab platform
I.g. Richardson - One of the best experts on this subject based on the ideXlab platform.
-
The mechanism of supplementary cementitious materials enhancing the water resistance of magnesium oxychloride cement (MOC): A comparison between Pulverized Fuel ash and incinerated sewage sludge ash
'Elsevier BV', 2020Co-Authors: He P, I.g. Richardson, Cs Poon, Tsang DcwAbstract:Magnesium oxychloride cement (MOC) pastes incorporating supplementary cementitious materials (SCMs) including Pulverized Fuel ash (PFA) and incinerated sewage sludge ash (ISSA) were examined by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) with energy dispersive X-ray spectrometry (EDX). The result showed that the mechanism of PFA and ISSA in improving the water resistance of MOC paste is similar, even though the molar ratios of the hydration product in the ISSA-incorporated paste and the PFA-incorporated paste were different. The active phases in PFA or ISSA could react with MgO and produce an amorphous phase (amorphous magnesium aluminosilicate gel), which was interspersed with Phase 5 and changed the morphology of Phase 5 to fibroid or lath-like phases. These fibroid or lath-like phases interlocked with each other and also connected with the amorphous phase in the matrix to form a stable compact structure. Therefore, the water resistance of MOC was improved. The ISSA-blended MOC paste had higher water resistance compared to the PFA-blended MOC, which may be due to the different chemical composition of amorphous phase and the dissolved phosphorus from ISSA
-
micro and nano structural evolutions in white portland cement Pulverized Fuel ash cement pastes due to deionized water leaching
Cement and Concrete Research, 2018Co-Authors: S. Jia, I.g. RichardsonAbstract:Abstract Thin slices of white Portland cement-low calcium Pulverized Fuel ash (pfa) blended cement pastes containing 30 or 50% pfa were leached progressively in de-ionized water. The paste with 50% pfa was aged 13 years prior to leaching and those with 30% pfa were aged 1 and 13 years. Pastes were leached for up to 75 days and were characterized using thermal analysis, X-ray diffraction, analytical scanning and transmission electron microscopy, and solid-state nuclear magnetic resonance spectroscopy. Leaching affected the pastes in the following sequence: (i) crystals of Ca(OH)2 large enough to be resolved by backscattered electron imaging were removed completely prior to any effect on C-A-S-H; (ii) the Ca/Si ratio of C-A-S-H reduced from ≈ 1.4 to ≈ 1.0 whilst the aluminosilicate structure was unaffected; (iii) further reduction in the Ca/Si ratio of C-A-S-H was accompanied by lengthening of the aluminosilicate chains; (iv) the Ca/Si ratio of C-A-S-H reduced ultimately to ≈ 0.6.
-
Hydration of water- and alkali-activated white Portland cement pastes and blends with low-calcium Pulverized Fuel ash
Cement and Concrete Research, 2016Co-Authors: I.g. Richardson, A.v. Girão, R. Taylor, S. JiaAbstract:Abstract Pastes of white Portland cement (wPc) and wPc-Pulverized Fuel ash (pfa) blends were studied up to 13 years. The reaction of wPc with water was initially retarded in the presence of pfa particles but accelerated at intermediate ages. Reaction with KOH solution was rapid with or without pfa. A universal compositional relationship exists for the C-A-S-H in blends of Pc with aluminosilicate-rich SCMs. The average length of aluminosilicate anions increased with age and increasing Al/Ca and Si/Ca; greater lengthening in the blends was due to additional Al 3 + at bridging sites. The morphology of outer product C-A-S-H was always foil-like with KOH solution, regardless of chemical composition, but with water it had fibrillar morphology at high Ca/(Si + Al) ratios and foil-like morphology started to appear at Ca/(Si + Al) ≈ 1.2–1.3, which from the literature appears to coincide with changes in the pore solution. Foil-like morphology cannot be associated with entirely T-based structure.
S. Jia - One of the best experts on this subject based on the ideXlab platform.
-
micro and nano structural evolutions in white portland cement Pulverized Fuel ash cement pastes due to deionized water leaching
Cement and Concrete Research, 2018Co-Authors: S. Jia, I.g. RichardsonAbstract:Abstract Thin slices of white Portland cement-low calcium Pulverized Fuel ash (pfa) blended cement pastes containing 30 or 50% pfa were leached progressively in de-ionized water. The paste with 50% pfa was aged 13 years prior to leaching and those with 30% pfa were aged 1 and 13 years. Pastes were leached for up to 75 days and were characterized using thermal analysis, X-ray diffraction, analytical scanning and transmission electron microscopy, and solid-state nuclear magnetic resonance spectroscopy. Leaching affected the pastes in the following sequence: (i) crystals of Ca(OH)2 large enough to be resolved by backscattered electron imaging were removed completely prior to any effect on C-A-S-H; (ii) the Ca/Si ratio of C-A-S-H reduced from ≈ 1.4 to ≈ 1.0 whilst the aluminosilicate structure was unaffected; (iii) further reduction in the Ca/Si ratio of C-A-S-H was accompanied by lengthening of the aluminosilicate chains; (iv) the Ca/Si ratio of C-A-S-H reduced ultimately to ≈ 0.6.
-
Hydration of water- and alkali-activated white Portland cement pastes and blends with low-calcium Pulverized Fuel ash
Cement and Concrete Research, 2016Co-Authors: I.g. Richardson, A.v. Girão, R. Taylor, S. JiaAbstract:Abstract Pastes of white Portland cement (wPc) and wPc-Pulverized Fuel ash (pfa) blends were studied up to 13 years. The reaction of wPc with water was initially retarded in the presence of pfa particles but accelerated at intermediate ages. Reaction with KOH solution was rapid with or without pfa. A universal compositional relationship exists for the C-A-S-H in blends of Pc with aluminosilicate-rich SCMs. The average length of aluminosilicate anions increased with age and increasing Al/Ca and Si/Ca; greater lengthening in the blends was due to additional Al 3 + at bridging sites. The morphology of outer product C-A-S-H was always foil-like with KOH solution, regardless of chemical composition, but with water it had fibrillar morphology at high Ca/(Si + Al) ratios and foil-like morphology started to appear at Ca/(Si + Al) ≈ 1.2–1.3, which from the literature appears to coincide with changes in the pore solution. Foil-like morphology cannot be associated with entirely T-based structure.
Daniel C W Tsang - One of the best experts on this subject based on the ideXlab platform.
-
comparison of glass powder and Pulverized Fuel ash for improving the water resistance of magnesium oxychloride cement
Cement & Concrete Composites, 2018Co-Authors: Ping Ping He, Chi Sun Poon, Daniel C W TsangAbstract:Abstract The water resistance of magnesium oxychloride cement (MOC) incorporating glass powder (GP) and Pulverized Fuel ash (PFA) with and without CO2 curing was investigated in terms of the strength retention coefficient and the volume stability. The microstructure was studied using quantitative X-ray diffraction (QXRD), thermogravimetry (TG), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The results show that the effect of incorporating GP on the water resistance is much lower than that of PFA due to the lower pozzolanic activity of GP generating a lower amount of magnesium silica hydrate gel (M-S-H gel). The MOC incorporated with GP or PFA showed high water resistance after CO2 curing due to the higher quantity of amorphous gel that formed a much denser interlocking network.
-
effect of Pulverized Fuel ash and co2 curing on the water resistance of magnesium oxychloride cement moc
Cement and Concrete Research, 2017Co-Authors: Ping Ping He, Chi Sun Poon, Daniel C W TsangAbstract:Abstract This paper presents a study on the use of Pulverized Fuel ash (PFA) to improve the water resistance of magnesium oxychloride cement (MOC). Strength retention coefficients and volume stability were tested to evaluate the water resistance of MOC, in which the addition of PFA resulted in a remarkable improvement. The characterization of hydration products before and after water immersion was carried out using quantitative X-ray diffraction (QXRD), thermogravimetric (TG), Fourier-transformed infrared spectroscopy (FTIR) and scanning electron microscope (SEM). With the Q-XRD analysis, it was shown that the addition of PFA could result in the great increase of the amount of amorphous phase during air curing. This amorphous gel was identified as a mixture of magnesium-chloride-silicate-hydrate gel (M-Cl-S-H gel) and magnesium-chloride-hydrate gel (M-Cl-H gel) by elemental mapping scanning. It suggested that PFA could not only react with MOC to form M-Cl-S-H gel, but also change the morphology of magnesium oxychloride. The generation of insoluble M-Cl-S-H gel and M-Cl-H gel and densification of the microstructure contributed to the improvement of the water resistance of MOC. The MOC mortar expanded during air curing due to the hydration of excess MgO. Water immersion led to more expansion of MOC mortar as a result of the continuously hydration of excess MgO and the formation of Mg(OH) 2 . Adding PFA could increase the expansion of MOC mortar during air curing, which may because the amorphous gel could remain more water and benefit to the hydration of MgO. While, the addition of PFA could decrease the expansion of cement mortar during water immersion perhaps due to the reduction of the content of excess MgO and the insoluble amorphous-gel-layer that protect the MgO from hydration. Moreover, CO 2 curing could further improve the performance of the PFA-blended MOC due to the formation of a higher content of amorphous gel.
Günter Scheffknecht - One of the best experts on this subject based on the ideXlab platform.
-
the impact of an additive on fly ash formation transformation from wood dust combustion in a lab scale Pulverized Fuel reactor
Renewable Energy, 2019Co-Authors: A. Fuller, Jörg Maier, Yinka Omidiji, Tillman Viefhaus, Günter ScheffknechtAbstract:Abstract The quality of fly ash from wood dust combustion with an alumina-silicate additive in a laboratory scale Pulverized Fuel reactor is assessed. Fly ash analyses include XRD, SEM-EDX, micro-Raman spectroscopy, ICP-OES, and mobility of elements. XRD results show that the addition of the additive change the fly ash to a pozzolanic nature, improving its quality for applications that follow strict material provisions. SEM analyses showed the morphology of fly ash particles changed to having more spherical smaller particles that involves much fewer larger particles covered by sticky fly ash particles on the surface too. The reduction of irregular particles and the increase in spherical particles improve the fly ash quality in concrete use. Mobility results showed a decrease in the amount of some potentially hazardous elements leached from the fly ash generated with the additive. Results from micro-Raman spectroscopy had the added value of identifying mineral phases for particles associated with a scale size, giving rise to determination of mineral phases for the different fly ash size fractions or particles. The study shows that an expansion of EN 450-1 is warranted for consideration to include an additive with combustion of higher amounts of a greenwood, or only with a greenwood, or with co-firing lower amounts of other biomass types in order to acquire fly ash in compliance with the standard.
-
use of wood dust fly ash from an industrial Pulverized Fuel facility for rendering
Construction and Building Materials, 2018Co-Authors: A. Fuller, Jörg Maier, Michael Stegmaier, Norbert Schulz, Martin Menke, Hans Schellhorn, Friedrich Knodler, Günter ScheffknechtAbstract:Abstract Wood dust II fly ash, which was generated after boiler retrofit (implementation of low-NOx burners combined with over-fire air), apparently is an enhanced quality for rendering. This is attributed to the mineral phases formed, an increase in the amount of free lime, and performance test results. After accelerated aging tests, the wood dust II fly ash showed no visible occurrence of cracks or detachment of the render base coat from the substrate. Tensile strength values met the applicable limit requirement of 8 MPa. The results contribute to a sustainable ash management for wood fly ash from Pulverized Fuel facilities.
-
Results of fly ash quality for disposal options from high thermal shares up to pure biomass combustion in a pilot-scale and large scale Pulverized Fuel power plants
Renewable Energy, 2015Co-Authors: A. Fuller, Marta Carbó, P. Savat, J. Kalivodova, Jörg Maier, Günter ScheffknechtAbstract:This work evaluated fly ash quality from combustion of high thermal shares of biomass Fuels. Woody biomass was (co)combusted in an industrial scale Pulverized Fuel power plant, and a herbaceous biomass was co-combusted in a pilot-scale test facility. Ashes from the electrostatic precipitator were collected and evaluated for chemical compounds, leaching behavior, and mechanical properties. Results from the large-scale industrial Pulverized Fuel showed the ashes still had good reactivity and mechanical properties according to EN450-1, which is a good unexpected occurrence regarding strength development. Results from the pilot-scale test facility showed that a herbaceous biomass co-fired up to 50% thermal share does not seem to have any negative impact on existing fly ash utilization routes. It is concluded that co-firing clean woody biomass at a very high thermal share and co-firing a high thermal share of a herbaceous biomass with lignite would not change current utilization practices. In practice ashes from high thermal shares are not used due to safeguards in standards form a lack of experience from enough performance testing. Thus, the findings can lead to support for standards that incorporate other assessment methods for biomass fly ash utilization requirements.
Ping Ping He - One of the best experts on this subject based on the ideXlab platform.
-
comparison of glass powder and Pulverized Fuel ash for improving the water resistance of magnesium oxychloride cement
Cement & Concrete Composites, 2018Co-Authors: Ping Ping He, Chi Sun Poon, Daniel C W TsangAbstract:Abstract The water resistance of magnesium oxychloride cement (MOC) incorporating glass powder (GP) and Pulverized Fuel ash (PFA) with and without CO2 curing was investigated in terms of the strength retention coefficient and the volume stability. The microstructure was studied using quantitative X-ray diffraction (QXRD), thermogravimetry (TG), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The results show that the effect of incorporating GP on the water resistance is much lower than that of PFA due to the lower pozzolanic activity of GP generating a lower amount of magnesium silica hydrate gel (M-S-H gel). The MOC incorporated with GP or PFA showed high water resistance after CO2 curing due to the higher quantity of amorphous gel that formed a much denser interlocking network.
-
effect of Pulverized Fuel ash and co2 curing on the water resistance of magnesium oxychloride cement moc
Cement and Concrete Research, 2017Co-Authors: Ping Ping He, Chi Sun Poon, Daniel C W TsangAbstract:Abstract This paper presents a study on the use of Pulverized Fuel ash (PFA) to improve the water resistance of magnesium oxychloride cement (MOC). Strength retention coefficients and volume stability were tested to evaluate the water resistance of MOC, in which the addition of PFA resulted in a remarkable improvement. The characterization of hydration products before and after water immersion was carried out using quantitative X-ray diffraction (QXRD), thermogravimetric (TG), Fourier-transformed infrared spectroscopy (FTIR) and scanning electron microscope (SEM). With the Q-XRD analysis, it was shown that the addition of PFA could result in the great increase of the amount of amorphous phase during air curing. This amorphous gel was identified as a mixture of magnesium-chloride-silicate-hydrate gel (M-Cl-S-H gel) and magnesium-chloride-hydrate gel (M-Cl-H gel) by elemental mapping scanning. It suggested that PFA could not only react with MOC to form M-Cl-S-H gel, but also change the morphology of magnesium oxychloride. The generation of insoluble M-Cl-S-H gel and M-Cl-H gel and densification of the microstructure contributed to the improvement of the water resistance of MOC. The MOC mortar expanded during air curing due to the hydration of excess MgO. Water immersion led to more expansion of MOC mortar as a result of the continuously hydration of excess MgO and the formation of Mg(OH) 2 . Adding PFA could increase the expansion of MOC mortar during air curing, which may because the amorphous gel could remain more water and benefit to the hydration of MgO. While, the addition of PFA could decrease the expansion of cement mortar during water immersion perhaps due to the reduction of the content of excess MgO and the insoluble amorphous-gel-layer that protect the MgO from hydration. Moreover, CO 2 curing could further improve the performance of the PFA-blended MOC due to the formation of a higher content of amorphous gel.
