The Experts below are selected from a list of 90 Experts worldwide ranked by ideXlab platform
Josette Camilleri - One of the best experts on this subject based on the ideXlab platform.
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the microstructure and surface morphology of radiopaque tricalcium silicate Cement exposed to different curing conditions
Dental Materials, 2012Co-Authors: L.m. Formosa, Bertram Mallia, T. Bull, Josette CamilleriAbstract:Abstract Objective Tricalcium silicate is the major constituent phase in mineral trioxide aggregate (MTA). It is thus postulated that pure tricalcium silicate can replace the Portland Cement Component of MTA. The aim of this research was to evaluate the microstructure and surface characteristics of radiopaque tricalcium silicate Cement exposed to different curing conditions namely at 100% humidity or immersed in either water or a simulated body fluid at 37 °C. Methods The materials under study included tricalcium silicate and Portland Cements with and without the addition of bismuth oxide radiopacifier. Material characterization was performed on hydrated Cements using a combination of scanning electron microscopy (SEM) with X-ray energy dispersive (EDX) analyses and X-ray diffraction (XRD) analyses. Surface morphology was further investigated using optical profilometry. Testing was performed on Cements cured at 100% humidity or immersed in either water or Hank's balanced salt solution (HBSS) for 1 and 28 days at 37 °C. In addition leachate analysis was performed by X-ray fluorescence of the storage solution. The pH of the storage solution was assessed. Results All the Cements produced calcium silicate hydrate and calcium hydroxide on hydration. Tricalcium silicate showed a higher reaction rate than Portland Cement and addition of bismuth oxide seemed to also increase the rate of reaction with more calcium silicate hydrate and calcium hydroxide being produced as demonstrated by SEM and XRD analysis and also by surface deposits viewed by the optical profilometer. Cement immersion in HBSS resulted in the deposition of calcium phosphate during the early stages following immersion and extensive calcification after 28 days. The pH of all storage solutions was alkaline. The immersion in distilled water resulted in a higher pH of the solution than when the Cements were immersed in HBSS. Leachate analysis demonstrated high calcium levels in all Cements tested with higher levels in tricalcium silicate and bismuth replaced Cements. Significance Tricalcium silicate Cement is more bioactive than Portland Cement as demonstrated by various characterization techniques. The bioactivity was monitored by measuring the production of calcium hydroxide and the formation of calcium phosphate when in contact with simulated body fluids.
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Characterization and hydration kinetics of tricalcium silicate Cement for use as a dental biomaterial
Dental Materials, 2011Co-Authors: Josette CamilleriAbstract:Abstract Objectives Investigation and characterization of the replaCement of the Portland Cement Component in mineral trioxide aggregate (MTA) with tricalcium silicate Cement which is manufactured using the sol-gel method from pure raw materials. Methods Tricalcium silicate and Portland Cement were characterized by viewing under the scanning electron microscope (SEM) and surface imaging and elemental analysis with X-ray energy dispersive analysis (EDX), and by X-ray diffraction analysis with Rietveld refinement. In addition the hydration products of the material after 28 days of curing were evaluated by plotting atomic ratio plots from the EDX data. The Cement leachate was evaluated for pH and chemical composition by inductively coupled plasma. Results Portland Cement was composed of 68% tricalcium silicate. The tricalcium silicate Cement was 99% pure. On hydration both Cements produced calcium silicate hydrate and calcium hydroxide. The calcium hydroxide was leached in solution with higher leaching in HBSS. The leaching of calcium hydroxide in solution resulted in an alkaline pH. The reaction of calcium with the phosphorus present in HBSS resulting in the deposition of calcium phosphate on the Cement surface. Significance Tricalcium silicate could prospectively replace the Portland Cement Component in MTA.
Ravindra K. Dhir - One of the best experts on this subject based on the ideXlab platform.
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use of incinerated ash as a Cement Component in concrete compressive strength modelling
Magazine of Concrete Research, 2019Co-Authors: Ciaran J Lynn, Ravindra K. Dhir, Gurmel S GhataoraAbstract:This paper presents a model for the estimation of the compressive strength of concrete using incinerated ashes, municipal incinerated bottom ash and sewage sludge ash as an addition. Based on sourc...
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sewage sludge ash characteristics and potential for use in concrete
Construction and Building Materials, 2015Co-Authors: Ciaran J Lynn, Ravindra K. Dhir, Gurmel S Ghataora, Roger WestAbstract:Abstract Sewage sludge ash (SSA) use in concrete related applications is assessed through systematic review involving analysis and evaluation of the global literature found published since 1983. The material characteristics indicate potential for various applications: in small dosages as raw feed in Portland Cement production, as fine and filler aggregates, or in ground form as Cement Component, with manageable effects on performance. Using manufactured SSA aggregate, concrete strength suitable for structural applications and lightweight properties comparable to Leca are attainable. SSA can be used in bulk, in controlled low strength materials (CLSM), aerated and foamed concretes. Reported case studies give encouraging signals.
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carbonation resistance of fly ash concrete
Magazine of Concrete Research, 2015Co-Authors: Chao Qun Lye, Ravindra K. Dhir, Gurmel S GhataoraAbstract:Based on systematic analysis, evaluation and synthesis of a 30 000 strong data matrix generated from 213 studies from 33 countries published since 1968, this paper details the extent of research that has been undertaken and discusses the effect of fly ash (FA) on the carbonation and carbonation-induced corrosion of concrete. It is shown that FA as a Cement Component, such as those adopted in BS EN 197-1:2011, increases the carbonation rate of concrete, both when concrete is designed in terms of equal water/Cement ratio or strength, though with the latter to a lesser extent. This increase in carbonation has also been confirmed for in-service concrete. The net effect of FA content on the carbonation of concrete is dependent upon the combination of mix design, curing and exposure related parameters. FA in concrete is also shown to increase the corrosion of reinforCement, which can only be overcome by increasing the cover to reinforCement, concrete strength, or a combination of the two, beyond those specified...
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characterization of conditioned pulverized fuel ash for use as a Cement Component in concrete
Magazine of Concrete Research, 1999Co-Authors: M J Mccarthy, P A J Tittle, Ravindra K. DhirAbstract:This paper considers the influence of moisture addition (conditioning) to PFA of up to 40% by mass on its physical and chemical properties and performance as a Cement Component in concrete. The work examined conditioned PFA, covering a range of fineness levels and lime contents, stored for up to 18 months, either in the laboratory or in stockpiles established at four UK power stations. Data for laboratory-conditioned PFA indicated progressive particle agglomeration (mainly in the finer fractions) with storage period, which was greatest at moisture levels of 10–20% and for material with total and free lime contents in excess of 3·0% and 0·1%, respectively. Corresponding increases in water demand and reductions in strength factor were also noted with conditioned material. Other changes, including increased LOI, reduced free lime content and formation of hydration products such as bassanite and gypsum, indicated that the effects were due to chemical activity. However, no significant changes to bulk oxide, mo...
Gurmel S Ghataora - One of the best experts on this subject based on the ideXlab platform.
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use of incinerated ash as a Cement Component in concrete compressive strength modelling
Magazine of Concrete Research, 2019Co-Authors: Ciaran J Lynn, Ravindra K. Dhir, Gurmel S GhataoraAbstract:This paper presents a model for the estimation of the compressive strength of concrete using incinerated ashes, municipal incinerated bottom ash and sewage sludge ash as an addition. Based on sourc...
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sewage sludge ash characteristics and potential for use in concrete
Construction and Building Materials, 2015Co-Authors: Ciaran J Lynn, Ravindra K. Dhir, Gurmel S Ghataora, Roger WestAbstract:Abstract Sewage sludge ash (SSA) use in concrete related applications is assessed through systematic review involving analysis and evaluation of the global literature found published since 1983. The material characteristics indicate potential for various applications: in small dosages as raw feed in Portland Cement production, as fine and filler aggregates, or in ground form as Cement Component, with manageable effects on performance. Using manufactured SSA aggregate, concrete strength suitable for structural applications and lightweight properties comparable to Leca are attainable. SSA can be used in bulk, in controlled low strength materials (CLSM), aerated and foamed concretes. Reported case studies give encouraging signals.
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carbonation resistance of fly ash concrete
Magazine of Concrete Research, 2015Co-Authors: Chao Qun Lye, Ravindra K. Dhir, Gurmel S GhataoraAbstract:Based on systematic analysis, evaluation and synthesis of a 30 000 strong data matrix generated from 213 studies from 33 countries published since 1968, this paper details the extent of research that has been undertaken and discusses the effect of fly ash (FA) on the carbonation and carbonation-induced corrosion of concrete. It is shown that FA as a Cement Component, such as those adopted in BS EN 197-1:2011, increases the carbonation rate of concrete, both when concrete is designed in terms of equal water/Cement ratio or strength, though with the latter to a lesser extent. This increase in carbonation has also been confirmed for in-service concrete. The net effect of FA content on the carbonation of concrete is dependent upon the combination of mix design, curing and exposure related parameters. FA in concrete is also shown to increase the corrosion of reinforCement, which can only be overcome by increasing the cover to reinforCement, concrete strength, or a combination of the two, beyond those specified...
L.m. Formosa - One of the best experts on this subject based on the ideXlab platform.
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the microstructure and surface morphology of radiopaque tricalcium silicate Cement exposed to different curing conditions
Dental Materials, 2012Co-Authors: L.m. Formosa, Bertram Mallia, T. Bull, Josette CamilleriAbstract:Abstract Objective Tricalcium silicate is the major constituent phase in mineral trioxide aggregate (MTA). It is thus postulated that pure tricalcium silicate can replace the Portland Cement Component of MTA. The aim of this research was to evaluate the microstructure and surface characteristics of radiopaque tricalcium silicate Cement exposed to different curing conditions namely at 100% humidity or immersed in either water or a simulated body fluid at 37 °C. Methods The materials under study included tricalcium silicate and Portland Cements with and without the addition of bismuth oxide radiopacifier. Material characterization was performed on hydrated Cements using a combination of scanning electron microscopy (SEM) with X-ray energy dispersive (EDX) analyses and X-ray diffraction (XRD) analyses. Surface morphology was further investigated using optical profilometry. Testing was performed on Cements cured at 100% humidity or immersed in either water or Hank's balanced salt solution (HBSS) for 1 and 28 days at 37 °C. In addition leachate analysis was performed by X-ray fluorescence of the storage solution. The pH of the storage solution was assessed. Results All the Cements produced calcium silicate hydrate and calcium hydroxide on hydration. Tricalcium silicate showed a higher reaction rate than Portland Cement and addition of bismuth oxide seemed to also increase the rate of reaction with more calcium silicate hydrate and calcium hydroxide being produced as demonstrated by SEM and XRD analysis and also by surface deposits viewed by the optical profilometer. Cement immersion in HBSS resulted in the deposition of calcium phosphate during the early stages following immersion and extensive calcification after 28 days. The pH of all storage solutions was alkaline. The immersion in distilled water resulted in a higher pH of the solution than when the Cements were immersed in HBSS. Leachate analysis demonstrated high calcium levels in all Cements tested with higher levels in tricalcium silicate and bismuth replaced Cements. Significance Tricalcium silicate Cement is more bioactive than Portland Cement as demonstrated by various characterization techniques. The bioactivity was monitored by measuring the production of calcium hydroxide and the formation of calcium phosphate when in contact with simulated body fluids.
Michael L. Koenigstein - One of the best experts on this subject based on the ideXlab platform.
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Use of Vitreous-Ceramic Coatings on Reinforcing Steel 349 Use of Vitreous-Ceramic Coatings on Reinforcing Steel for Pavements
2014Co-Authors: Charles A. Weiss, Sean W. Morefield, Philip G. Malone, Michael L. KoenigsteinAbstract:An innovative vitreous-ceramic coating for reinforcing steel that incorporates reactive calcium silicates from portland Cement in an alkali-resistant glass has been shown both to increase the bond between the concrete to the reinforcing steel and to protect the steel from corrosion. The new enamel coating eliminates the weak layer that is associated with the interface between the steel and surrounding concrete. The vitreous coating is applied to the steel using the same proc-ess involved in porcelain enameling. In applying the enamel, the rod is coated with a porcelain slip containing portland Cement and heated to approximately 1,562 °F (850 °C) for 5 to 10 minutes to allow the molten glass to fuse to the surface of the iron and the portland-Cement Component to become bonded to and embedded in the glass. The result is a tough, abrasion-resistant, hermetically-tight coating that develops the adhering properties of a portland-Cement paste when contacted by fresh concrete. Bleed water from the fresh concrete that normally produces a weak interfacial transition zone is taken up by the hydration of the surface layer of reactive calcium silicate. After only 7 days of curing, the chemical bond that forms is typically three to four times greater than that observe