Setting and Thermal Reactions of Phosphate Investments

Neiman, Robert; Sarma, Atul C.

doi:10.1177/00220345800590090401

Cited by 69 publications

(16 citation statements)

References 3 publications

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“…4); again, no crystalline reflections were identified that could be associated with a dehydrated KMgPO 4 phase. As discussed above, it is postulated that KMgPO 4 is non-crystalline between 200 °C -700 °C [25][26][27] , as a result of dehydration of struvite-K. Diffuse scattering associated with the glassy slag fraction is reported between 24 , however the diffuse scattering in the 200 °C diffraction pattern was evident over a wider range (between ), suggesting that more than one amorphous phase could be present. The quartz identified at 200 °C is believed to be contamination from the cleaning media (sand) used during grinding.…”

Section: Omentioning

confidence: 98%

Evolution of phase assemblage of blended magnesium potassium phosphate cement binders at 200° and 1000°C

Gardner

Lejeune

Corkhill

et al. 2015

Advances in Applied Ceramics

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The fire performance of magnesium potassium phosphate cement (MKPC) binders blended with fly ash (FA) and ground granulated blast furnace slag (GBFS) was investigated up to 1000 °C using XRD, TGA, and SEM techniques. The FA/MKPC and GBFS/MKPC binders dehydrate above 200 °C to form amorphous KMgPO 4 , concurrent with volumetric and mass changes. Above 1000 °C, additional crystalline phases were formed and microstructural changes occurred, although no cracking or spalling of the samples was observed. These results indicate that FA/MKPC and GBFS/MKPC binders are expected to have satisfactory fire performance under the fire scenario conditions relevant to the operation of a UK or other geological disposal facility.

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Section: Omentioning

confidence: 98%

Evolution of phase assemblage of blended magnesium potassium phosphate cement binders at 200° and 1000°C

Gardner

Lejeune

Corkhill

et al. 2015

Advances in Applied Ceramics

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“…The inclusion of FA in MKPC enhances the workability of the binder via the "ball-bearing effect" of the spherical particles [6,[9][10][11]. Several studies [6,12,13] based on FA/MKPC blended binders have suggested that FA simply acts as a diluent or inert filler, that modifies the aesthetics of MKPC to be compatible to traditional Portland cement, which has been deemed important for rapid-repair applications [9]. Conversely, others hypothesise that FA replacement promotes high mechanical strength in FA/MKPC binders, as a consequence of the formation of a secondary amorphous phase containing silicon-phosphate bonds [12,14].…”

Section: Introductionmentioning

confidence: 99%

Characterisation of magnesium potassium phosphate cements blended with fly ash and ground granulated blast furnace slag

Gardner

Bernal

Walling

et al. 2015

Cement and Concrete Research

272

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Magnesium potassium phosphate cements (MKPCs), blended with 50 wt.% fly ash (FA) or ground granulated blast furnace slag (GBFS) to reduce heat evolution, water demand and cost, were assessed using compressive strength, X-ray diffraction (XRD), scanning electron microscopy (SEM) and nuclear magnetic resonance (NMR) spectroscopy on 25 Mg, 27 Al, 29 Si, 31 P and 39 K nuclei. We present the first definitive evidence that dissolution of the glassy aluminosilicate phases of both FA and GBFS occurred under the pH conditions of MKPC. In addition to the main binder phase, struvite-K, an amorphous orthophosphate phase was detected in FA/MKPC and GBFS/MKPC systems. It was postulated that an aluminium phosphate phase was formed, however, no significant Al-O-P interactions were identified. High-field NMR analysis of the GBFS/MKPC system indicated the potential formation of a potassium-aluminosilicate phase. This study demonstrates the need for further research on these binders, as both FA and GBFS are generally regarded as inert fillers within MKPC.

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“…To date, research and development is still ongoing for new investment materials which would bring casting quality and accuracy to new heights. For phosphate-bonded investments, numerous investigations have been carried out to examine the following in an unrelenting search for improvements and betterments: effects of mixing methods and mixing conditions on the setting expansion and compressive strength of casting investments 11,12) , effects of the properties/characteristics of casting investments on cast smoothness and dimensional accuracy 11) , reaction of investment with cobalt-chromium alloys at high casting temperatures 13) , factors which affect the setting and thermal expansions of casting investments 14,15) , effects of investment's potential expansion, hot strength, and deformation at elevated temperatures on casting accuracy 16,17) , and factors which influence the gas permeability and castability of casting investments 18,19) . One of the recent innovations in investment casting was the rapid-heating phosphate-bonded investment 20) .…”

Section: Introductionmentioning

confidence: 99%

Porosity of dental phosphate-bonded investments after setting and heating processes

2012

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Porosities of set and burnout compacts of phosphate-bonded investments were determined. A gas pycnometer was used to measure the volumes, and hence the densities, of fine powders and porous compacts. Porosities of set and burnout compacts were then obtained from these data for as-received powders and dry set compacts by a numerical simulation method, subsequently leading on to the estimated compositions of conventional and rapid-heating investments used in this study. Excess water content in the hardening investment compact was evaluated as a function of setting time elapsed from the start of mixing. Porosities were about 24-32% for set compacts and 43% for burnout compacts, which well agreed with the numerically computed results. It was concluded that the functional composition of investment powder needed to achieve the optimal porosity as well as process parameters such as water-powder (W/P) ratio and keeping time of mixed investment casting slurry before heat treatment could be determined using the numerical simulation method developed in this study.

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Setting and Thermal Reactions of Phosphate Investments

Cited by 69 publications

References 3 publications

Evolution of phase assemblage of blended magnesium potassium phosphate cement binders at 200° and 1000°C

Evolution of phase assemblage of blended magnesium potassium phosphate cement binders at 200° and 1000°C

Characterisation of magnesium potassium phosphate cements blended with fly ash and ground granulated blast furnace slag

Porosity of dental phosphate-bonded investments after setting and heating processes

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