Topic
Ettringite
About: Ettringite is a research topic. Over the lifetime, 2702 publications have been published within this topic receiving 67056 citations. The topic is also known as: woodfordite.
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01 Jan 1994
TL;DR: In this paper, chemical and microstructural aspects of delayed ettringite formation are reviewed, and it is shown that the rate and ultimate extent of expansion are influenced by factors of three types: chemistry, paste microstructure, which determines the stresses produced by its formation.
Abstract: Abstract Delayed ettringite formation (DEF) can damage concrete that has experienced a temperature above about 70°C. Claims that slow release of sulfate from the clinker can have a similar effect in concrete not thus heated are unsupported. Chemical and microstructural aspects of DEF are reviewed. Expansion results from formation of ettringite crystals of submicrometre size in the paste, the larger crystals readily observed in cracks and voids being recrystallisation products. The rate and ultimate extent of expansion are influenced by factors of three types: chemistry, which determines how much ettringite can be formed; paste microstructure, which determines the stresses produced by its formation; and concrete or mortar microstructure, which determines the response of the material to those stresses. Alkali present before the end of the heat treatment can increase expansion, but when present subsequently, it decreases expansion by inhibiting ettringite formation. Leaching therefore promotes expansion.
34 citations
TL;DR: In this article, three types of concrete were made from granite and quartz sand, coarse and fine flint, and coarse and finelimestone, and they were cast and cured at 95-100°C and subsequently stored at room temperature under water.
Abstract: Portland cement mortars were made from natural quartz and crushed limestone sands, and combinations of thetwo. Three types of concrete were made from granite and quartz sand, coarse and fine flint, and coarse and finelimestone. Mortar and concrete prisms were cast and cured at 95–100°C and subsequently stored at roomtemperature under water. The quartz sand mortars exhibited large expansions within the first year but thelimestone mortars remained stable even after 6 years. The ultimate expansion of those mortars with combinationsof limestone and quartz aggregate had intermediate values. The granite aggregate concretes expanded readily butthe limestone and the flint concretes started to expand only after very long induction periods. X ray diffraction,scanning electron microscopy with back-scattered electron imaging and X ray microanalysis were used to examinethe composition and microstructure of the hydration products. Differences in the features of ettringite bands thatdeveloped in the various heat-cured m...
34 citations
TL;DR: In this paper, the effect of elevated temperature curing on mortars and the phenomenon of delayed ettringite formation (DEF) was investigated, and it was shown that the ultimate levels of ettricite reached do not correspond to the magnitude of expansion observed.
Abstract: This paper reports some preliminary results from a study of the effect of elevated temperature curing on mortars and the phenomenon of delayed ettringite formation (DEF). Mortars made from cements with sulphate levels of 3%, 4%, and 5% and with 5% sulphate and added alkali were cured at 20 and 90° C and subsequently stored in water. Expansion measurements showed a pessimum effect with increasing S03 content. Mortars which expanded showed a corresponding decrease in strength. X-ray diffraction (XRD) studies indicated that no ettringite is present after heat treatment but re-forms over time within the material. However, the ultimate levels of ettringite reached do not correspond to the magnitude of expansion observed. X-ray microanalysis shows that immediately after the heat treatment the aluminate species and most of the sulphate species are incorporated within the C-S-H gel. The concentrations of these species decrease during expansion, such that at the end of expansion the amounts remaining correspond to the presence of AFm phase mixed with C-S-H.
34 citations
TL;DR: In this paper, a method for quantitative Xray diffraction analysis (QXDA) of three sulphate minerals frequently associated with building materials has been devised, including ettringite, thaumasite, and gypsum.
34 citations
TL;DR: In this article, the hydrogen NMR parameters T 1, T 2 and M oi of a white cement were monitored as a function of hydration time, from the nature and time evolution of the same 20 observables that eventually developed, a partial description of the dynamics of cement hydration was proposed.
34 citations