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“…The effect on the calculated amorphous content of R 900® is to increase it substantially from ∼5.6% to approximately 14%. Previous publications where the old amorphous content of SRM676 was used (Whitfield and Mitchell, 2003; Winburn et al , 2000) consequently Figure 4.Phase fractions ( wt %) against time for data collected in transmission.Figure 5.Portlandite phase fractions ( wt %) against time for data collected in both transmission and reflection. The corresponding textural index values are also shown on a second Y axis. underestimate the amorphous content.…”
Section: Methodsmentioning
confidence: 96%
“…Rietveld analysis also affords the opportunity to quantify the presence of amorphous materials, both within unhydrated and hydrated cements (Suherman et al , 2002; Whitfield and Mitchell, 2003). This is achieved by the addition of a known amount of a crystalline internal standard material.…”
Section: Introductionmentioning
confidence: 99%
“…The use of Rietveld refinement for quantitative phase analysis was first described in detail in 1987 ͑Rietveld, 1967; Hill and Howard, 1987͒. Its routine application to the quantification of complex mixtures, such as ordinary Portland cement, is a much more recent development, largely due to the introduction of innovations, such as convolution-based peak synthesis and fundamental parameters into Rietveld software ͑Cheary and Coelho, 1992͒. The reduction in the number of parameters required to describe the peaks of each phase makes such an analysis fairly routine with rapid acceptance within the commercial cement community for quality control ͑Scarlett et al., 2001͒. Rietveld analysis also affords the opportunity to quantify the presence of amorphous materials, both within unhydrated and hydrated cements ͑Suherman et al., 2002;Whitfield and Mitchell, 2003͒. This is achieved by the addition of a known amount of a crystalline internal standard material.…”
A study examining the feasibility, and possible necessity, of using transmission data from capillary mounted samples for quantitative analysis of hydrated cement systems was conducted. In order to obtain true quantitative results, the amorphous contents were determined by the addition of an internal standard. The amorphous content of the starting tricalcium silicate was found to be approximately 21–22 wt %, in close agreement with previously published results. The study revealed that the spherical harmonics preferential orientation correction may not be reliable with unmicronized hydrated cement materials in reflection geometry, as chemically unreasonable progressions in Portlandite content with time were observed. The data obtained from capillary measurements, however, exhibited little or no preferential orientation, and appeared to produce the progression of phase contents expected from the reaction. The use of capillaries would appear to be justified in some circumstances to obtain reliable quantitative results from hydrated cementitious materials. In this particular system, a significant fraction of calcium carbonate was present as aragonite, as well as the more usual calcite.
“…The effect on the calculated amorphous content of R 900® is to increase it substantially from ∼5.6% to approximately 14%. Previous publications where the old amorphous content of SRM676 was used (Whitfield and Mitchell, 2003; Winburn et al , 2000) consequently Figure 4.Phase fractions ( wt %) against time for data collected in transmission.Figure 5.Portlandite phase fractions ( wt %) against time for data collected in both transmission and reflection. The corresponding textural index values are also shown on a second Y axis. underestimate the amorphous content.…”
Section: Methodsmentioning
confidence: 96%
“…Rietveld analysis also affords the opportunity to quantify the presence of amorphous materials, both within unhydrated and hydrated cements (Suherman et al , 2002; Whitfield and Mitchell, 2003). This is achieved by the addition of a known amount of a crystalline internal standard material.…”
Section: Introductionmentioning
confidence: 99%
“…The use of Rietveld refinement for quantitative phase analysis was first described in detail in 1987 ͑Rietveld, 1967; Hill and Howard, 1987͒. Its routine application to the quantification of complex mixtures, such as ordinary Portland cement, is a much more recent development, largely due to the introduction of innovations, such as convolution-based peak synthesis and fundamental parameters into Rietveld software ͑Cheary and Coelho, 1992͒. The reduction in the number of parameters required to describe the peaks of each phase makes such an analysis fairly routine with rapid acceptance within the commercial cement community for quality control ͑Scarlett et al., 2001͒. Rietveld analysis also affords the opportunity to quantify the presence of amorphous materials, both within unhydrated and hydrated cements ͑Suherman et al., 2002;Whitfield and Mitchell, 2003͒. This is achieved by the addition of a known amount of a crystalline internal standard material.…”
A study examining the feasibility, and possible necessity, of using transmission data from capillary mounted samples for quantitative analysis of hydrated cement systems was conducted. In order to obtain true quantitative results, the amorphous contents were determined by the addition of an internal standard. The amorphous content of the starting tricalcium silicate was found to be approximately 21–22 wt %, in close agreement with previously published results. The study revealed that the spherical harmonics preferential orientation correction may not be reliable with unmicronized hydrated cement materials in reflection geometry, as chemically unreasonable progressions in Portlandite content with time were observed. The data obtained from capillary measurements, however, exhibited little or no preferential orientation, and appeared to produce the progression of phase contents expected from the reaction. The use of capillaries would appear to be justified in some circumstances to obtain reliable quantitative results from hydrated cementitious materials. In this particular system, a significant fraction of calcium carbonate was present as aragonite, as well as the more usual calcite.
“…The sample holders were filled using the front-loading procedure. The data obtained from XRD were interpreted using Bruker-DIFFRAC.EVA software and a Rietveld analysis [30,31] in order to quantify the amorphous and crystalline percentage. The fly ash surface area was determined using Brunauer Emmett Teller method by N 2 absorption [32,33].…”
This study reports the effect of heat curing at 120 °C on the geopolymeric reaction and strength evolution in brown coal fly ash based geopolymer mortar and concrete. Moreover, an examination of this temperature profile of large size geopolymer concrete specimens is also reported. The specimen temperature and size were observed to influence the conversion from the glassy (amorphous) phases to the crystalline phases and the microstructure development of the geopolymer. The temperature profile could be divided into three principal stages which correlated well with the proposed reaction mechanism for class F fly ash geopolymers. The geopolymerisation progressed more rapidly for the mortar specimens than the concrete specimens with 12 to 14 h providing an optimum curing time for the 50 mm mortar cubes and 24 h being the optimum time for the 100 mm concrete cubes. The 50 mm and 100 mm concrete specimens’ compressive strengths in excess of 30 MPa could be obtained at 7 days. The structural integrity was not achieved at the center of 200 mm and 300 mm concrete specimens following 24 h curing at 120 °C. Hence, the optimal curing time required to achieve the best compressive strength for brown coal geopolymer was identified as being dependent on the specimen size.
“…Le Saoût et al (2007) also noted that it is imperative to take into consideration the influence of refinement parameters on the quantification of amorphous contents. More research concerning the amorphous level of cements and clinkers was carried out by Whitfield and Mitchell (2003). They employed the internal standard method and calculated an amorphous content in the cement used of 18 to 25 wt %.…”
A suitable external standard method which was first described by O’Connor and Raven (1988) (“Application of the Rietveld refinement procedure in assaying powdered mixtures,” Powder Diffr. 3, 2–6) was used to determine the quantitative phase composition of a commonly used Ordinary Portland Cement (OPC). The method was also applied in order to determine amorphous contents in OPC. Also investigated were the impact of atomic displacement parameters and the microstrain on the calculated amorphous content. The investigations yielded evidence that said parameters do indeed exert an influence on the calculated amorphous content. On the basis of the data produced we can conclude that the method used is entirely to be recommended for the examination of OPC. No significant amorphous content could be proven in the OPC used.
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