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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TL;DR: In this article, a computerized focusing Huber-Guinier diffractometer was used to obtain the pattern of aluminate hydration reactions in Portland cements using X-ray diffraction.
Abstract: The aluminate hydration reactions in Portland cements were followed by X-ray diffraction. Using a computerized focusing Huber-Guinier diffractometer, the patterns were obtained from the pastes directly, without preliminary drying or grinding. It is shown that the widely accepted theories on the hydration of C3A in the presence of calcium sulfate cannot be applied generally to commercial Portland cements. Only in cases of pastes nearly free of CO2 will the ettlingite formed in the course of the induction period transform to monosulfate. In cement pastes containing more than about 0.5% CO2 the conversion is prevented and monosulfate is replaced by hemicarbonate or monocarbonate. The quantity of CO2 sufficient to replace monosulfate by carbonated AFm phases depends on the ratio of SO3 to C3A and the amount of available Al2O3. The results clearly show that with cements or concretes containing monosulfate the risk of delayed ettringite formation as a result of carbonation reactions should be taken into account. The interlayer sulfate groups in the crystal structure of monosulfate can be replaced by carbonate. This exchange results in increasing sulfate concentration in the pore solution and thus leads to delayed ettringite formation.
94 citations
Abstract: Calcium sulfoaluminate (CSA) cements are currently receiving a lot of attention because their manufacture produces less CO2 than ordinary Portland cement (OPC). However, it is essential to understand all parameters which may affect the hydration processes. This work deals with the study of the effect of several parameters, such as superplasticizer (SP), gypsum contents (10, 20 and 30 wt.%) and w/c ratio (0.4 and 0.5), on the properties of CSA pastes during early hydration. This characterization has been performed through rheological studies, Rietveld quantitative phase analysis of measured X-ray diffraction patterns, thermal analysis and mercury porosimetry for pastes, and by compressive strength measurements for mortars. The effect of the used SP on the rheological properties has been established. Its addition makes little difference to the amount of ettringite formed but strongly decreases the large pore fraction in the pastes. Furthermore, the SP role on compressive strength is variable, as it increases the values for mortars containing 30 wt.% gypsum but decreases the strengths for mortars containing 10 wt.% gypsum.
93 citations
TL;DR: In this paper, the distribution curves for ettringite, gypsum, and portlandite phases were obtained by using layer by layer XRD analysis and interpreted in terms of material damage due to sulfate attack.
92 citations
TL;DR: In this paper, a method that accelerates the ettringite formation in concrete has been used to study the impact of cement properties on DEF, and the results showed that delayed ettricite formation is likely to lead to swelling and cracking in structures which have undergone eartly age heating to a temperature of over 65°c.
Abstract: Delayed ettringite formation in concrete is likely to lead to swelling and cracking in structures which have undergone eartly age heating to a temperature of over 65°c. Application of a method that accelerates this process has made it possible to study the impact of cement properties on DEF.
92 citations
TL;DR: In this paper, the formation of ettringite at lower temperatures in the Portland cement/calcium aluminate cement, and the effect of calcium sulfate variety on the setting time of the ternary system and the strength development of its mortars at 0, 5, 10 and 20°C were investigated.
92 citations