R.N. Edmonds

Bio: R.N. Edmonds is an academic researcher. The author has contributed to research in topics: Monocalcium aluminate. The author has an hindex of 1, co-authored 1 publications receiving 55 citations.

The hydration of monocalcium aluminate at different temperatures

Abstract: The chemistry of hydration of monocalcium aluminate, CA, has been studied at several temperatures using conduction calorimetry, X-ray diffraction and other techniques. At 4 °C, hydration to the decahydrate CAH 10 occurs about 15 hours after mixing; this hydration time increases with increasing temperature up to 30 °C, and C 2 AH 8 appears as a hydration product. At 40 °C rapid hydration to C 2 AH 8 is followed over a period of weeks by the ‘conversion’ reaction producing C 3 AH 6 . The reaction of CA to form crystalline hydrates was monitored by X-ray diffraction analysis; the results indicate that hydration also produces significant amounts of noncrystalline material. The enthalpies of the reactions involved in hydration and ‘conversion’ were measured by conduction calorimetry.

Castable refractory concretes

Abstract: Castable refractories containing calcium aluminate cement (CAC) are used ubiquitously in a range of furnace lining applications in the iron and steel, cement, glass, ceramic, and petrochemical industries. This review outlines their development from conventional high cement materials, through low cement and ultra-low cement castables to the present materials which may be entirely free of CAC. Castables are defined in terms of both CaO content and installation procedure. Production routes, compositions, and microstructural evolution on hydration, setting, dehydration, and firing are described for pure CACs and castable refractories. The development of the low cement systems is discussed in terms of particle packing, dispersion, and rheology highlighting the influence of colloidal matrix additions of silica and alumina. Recent developments including cement free, self-flowing, shotcreting, and basic castables are described and the potential for carbon-containing systems evaluated.

2 – Calcium aluminate cements

Abstract: In terms of the length of time it has been produced, the volume produced and the breadth of applications, calcium aluminate cements are by far the most important class of non-Portland cements. Calcium aluminate cements are a relatively large family with a range of compositions which varies much more widely than Portland cement. Today the two major markets for calcium aluminate cement are in castable refractories and in dry mix mortars for special construction applications, which together account for around 80% of consumption. The use in technical concretes, for example, sewer linings, rapid repair, etc. is rather small. Calcium aluminate cements are known for their rapid strength gain, especially at low temperatures, superior durability across several categories and high temperature resistance. Their ability to consume water rapidly during hydration makes them a preferred component in building chemistry applications as this contributes to construction expediency. CACs are highly versatile materials that can be used as the full binding material, or as is more common, a component of a blended system where the contribution is based on the final desired properties.

Stability in the system CaO–Al2O3–H2O

Abstract: The solubility of AH 3 , CAH 10 , C 2 AH 7.5 , and C 3 AH 6 was determined experimentally at 7 to 40 °C and up to 570 days. During the reaction of CA, at 20 °C and above initially C 2 AH 7.5 formed which was unstable in the long-term. The solubility products calculated indicate that the solubilities of CAH 10 , C 2 AH 7.5 and C 4 AH 19 increase with temperature while the solubility of C 3 AH 6 decreases. Thus at temperatures above 20 °C, C 3 AH 6 is stable, while at lower temperature also CAH 10 and C 4 AH 19 are stable, depending on the C/A ratio. At early hydration times, CAH 10 can be stable initially at 30 °C and above, as the formation of amorphous AH 3 stabilises CAH 10 with respect to C 3 AH 6 + 2AH 3 . With time, as the solubility AH 3 decreases due to the formation of microcrystalline AH 3 , CAH 10 becomes unstable at 20 °C and above.

Chemical Synthesis and Characterization of Calcium Aluminate Powders

Abstract: The Pechini process was used to produce high-purity, monocalcium aluminate (CaAl 2 O 4 ) powders at temperatures as low as 900 o C. Absorption spectrometry and BET measurements revealed particles with sizes ranging from submicrometer to 100 μm, with specific surface areas as high as 10 m 2 /g. Auger electron spectrometry (AES) was used to study the progressive elimination of surface carbon from the organic burnout as a function of temperature. The growth kinetics of calcium aluminate crystallites from a polymeric precursor were studied during calcination as a function of temperature, using transmission electron microscopy (TEM)

Hydration of Calcium Aluminate Cements: A Solid‐State 27 Al NMR Study

Abstract: This paper presents the results of a study of the hydration of calcium monoaluminate (CA) and Lafarge Secar 71 (CA + CA2) using 27Al MAS and 1H-27 Al CPMAS NMR spectroscopy. CPMAS, high H0 magnetic field strengths (11.7 T), and high MAS spinning speeds (13–14 kHz) provide significant new information about the Al structural environments present during hydration and about the mechanisms of hydration. Important results include the following: (1) Hydrated Al(4) and Al(6) environments are present during the incubation period. This observation is consistent with previously published hydration models. (2) The overall conversion of Al(4) in unhydrated phases to Al(6) in hydrated phases and the crystalline phases detected by XRD are similar to the results of previous studies. (3) There are previously undetected hydrated reaction intermediates present during the main reaction stage. At temperatures above 25°C this phase contains Al(4), and at 4°C it contains Al(4) and possibly Al(5). The incubation period observed for this reaction may be related to the nucleation of this phase.