Hydrothermal processing of xonotlite based compositions

Abstract

Compositions based on pure xonotlite and those containing magnesium oxide have been synthesised in an autoclave under autogenous steam pressure at temperatures of 200, 225 and 250uC for 20 h. Products were characterised by thermal analysis, X-ray diffraction and microstructural studies. Average compressive strengths for monoliths up to 28 MPa were achieved, depending on curing conditions, which provides potential applications for such compositions as binders within an intermediate temperature range up to y600uC. These products show good dimensional stability when produced from relevant raw materials and near net shape articles could be produced.

Raman spectroscopic study of the mineral xonotlite Ca6Si6O17(OH)2—A component of plaster boards

“…Starting with a mechano-chemically semicrystalline phase with Ca/Si = 1, these authors prepared a series of xonotlite samples hydrothermally, at temperatures between 200 and 250 8C [9]. Other techniques have been used to study xonotlite including XPS, environmental SEM and X-ray diffraction [9,10].…”

“…Similarly it may also be found in autoclaved concrete blocks, but it certainly is not seen upon hydration of cement under normal conditions. Some studies of the synthesised analogue of xonotlite and mixtures with MgO with application as binding materials [10]. Black et al systematically investigated the role of synthesis conditions upon the structure and morphology of xonotlite [9].…”

Current themes in cement research

“…There are also a number of approaches based on traditional, i,e. Portland cement, binders, but with a non-traditional pre-or post-treatment step, such as sol-gel synthesis 82 or hydrothermal treatment 83,84 .…”

“…Recently there have been studies looking at replacing calcium with magnesium without significant changes in either performance or morphology 83 , or looking at changes in morphology with steam temperature or duration of treatment 84 . Research into hydrothermal treatments of silicate based systems is still ripe for further development, with a wide range of applications available for this low energy material.…”

Preparation of ultra-light xonotlite thermal insulation material using carbide slag

“…At last, these samples became thermal insulation materials after drying. So far, investigations on synthesis of xonotlite using quicklime as the calcareous material have been reported in literatures [9][10][11] . As a result, the ecosystem was destroyed badly by mining a large quantity of limestone which was used to produce quicklime.…”