Über das Potenzial von calciniertem Ton in zementgebundenen Systemen

Weise, Kira

doi:10.1007/978-3-658-28791-7

Cited by 7 publications

(3 citation statements)

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“…For the drying procedure with acetone, 3 g ± 0.05 g of the R 3 sample was gently hand-milled and washed three times with 5 mL of acetone (>99.5%) while continuing milling according to Röser and Weise [ 15 , 22 , 23 ]. For the reference sample (R 3 emulsion without SCM), seven aliquots of 5 mL of acetone were needed to dry the samples.…”

Section: Methodsmentioning

confidence: 99%

A Mass Balance Approach for Thermogravimetric Analysis in Pozzolanic Reactivity R3 Test and Effect of Drying Methods

2021

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The reactivity of supplementary cementitious materials (SCMs) is a key issue in the sustainability of cement-based materials. In this study, the effect of drying with isopropanol and acetone as well as the interpretation of thermogravimetric data on the results of an R3 test for evaluation of the SCM pozzolanic reaction were investigated. R3 samples consisting of calcium hydroxide, potassium hydroxide, potassium sulphate, water, and SCM were prepared. Besides silica fume, three different types of calcined clays were investigated as SCMs. These were a relatively pure metakaolin, a quartz-rich metakaolin, and a mixed calcined clay, where the amount of other types of clays was two times higher than the kaolinite content. Thermogravimetric analysis (TGA) was carried out on seven-day-old samples dried with isopropanol and acetone to stop the reaction processes. Additional calorimetric measurement of the R3 samples was carried out for evaluation of the reaction kinetics. Results show that drying with isopropanol is more suitable for analysis of R3 samples compared to acetone. The use of acetone results in increased carbonation and TGA mass losses until 40 (isothermal drying for 30 min) and 105 °C (ramp heating), indicating that parts of the acetone remain in the sample, causing problems in the interpretation of TGA data. A mass balance approach was proposed to calculate calcium hydroxide consumption from TGA data, while also considering the amount of carbonates in the sample and TGA data corrections of original SCMs. With this approach, an improvement of the linear correlation of TGA results and heat release from calorimetric measurement was achieved.

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Section: Methodsmentioning

confidence: 99%

A Mass Balance Approach for Thermogravimetric Analysis in Pozzolanic Reactivity R3 Test and Effect of Drying Methods

2021

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“…Clays benefit from a vast global availability [ 10 ], require relatively low temperatures for calcination (~750 °C) [ 7 , 11 , 12 ], and emit less CO 2 [ 13 , 14 ]. The main challenge concerning the use of local calcined clays as SCMs is to control the variation of their composition and its impact on the reactivity [ 7 , 9 , 11 , 12 , 15 , 16 , 17 , 18 ].…”

Section: Introductionmentioning

confidence: 99%

“…Metakaolin is obtained from the dehydroxylation of kaolinite, which occurs during a thermal activation between 400 °C and 800 °C [ 11 , 16 ]. The release of OH − ions results in an amorphous structure, called metakaolin, that is required for a pozzolanic reaction in cementitious systems [ 15 ]. The pozzolanic reaction of MK leads to the additional formation of hydrate phases along with the consumption of CH, resulting in an increase in the material strength [ 19 ].…”

Section: Introductionmentioning

confidence: 99%

Enhanced Metakaolin Reactivity in Blended Cement with Additional Calcium Hydroxide

et al. 2022

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This study aims to increase the pozzolanic reactivity of metakaolin (MK) in Portland cement (PC) blends by adding additional calcium hydroxide (CH_add) to the initial mixture. Cement paste samples were prepared with PC, MK and water with a water-to-binder ratio of 0.6. Cement replacement ratios were chosen from 5 to 40 wt.% MK. For higher replacement ratios, i.e., 20, 30 and 40 wt.% MK, CH_add was included in the mixture. CH_add-to-MK ratios of 0.1, 0.25 and 0.5 were investigated. Thermogravimetric analysis (TGA) was carried out to study the pozzolanic reactivity after 1, 7, 28 and 56 days of hydration. A modified mass balance approach was used to normalize thermogravimetric data and to calculate the calcium hydroxide (CH) consumption of samples with CH_add. Results showed that, without CH_add, a replacement ratio of 30 wt.% or higher results in the complete consumption of CH after 28 days at the latest. In these samples, the pozzolanic reaction of MK turned out to be restricted by the amount of CH available from the cement hydration. The increased amount of CH in the samples with CH_add resulted in an enhanced pozzolanic reaction of MK as confirmed by CH consumption measurements from TGA.

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Mechanische Aktivierung von Lehm

et al. 2023

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Lehm weist bekanntermaßen bauphysikalische Vorteile wie die Feuchtesorption bzw. Feuchteregulierung, Schalldämmung und das Wärmespeichervermögen auf. Verglichen mit anderen Baustoffen erweisen sich Festigkeiten wie die Druck‐ und Biegezugfestigkeit als niedrig bzw. nachteilig. Zur Optimierung von Lehm als Baustoff, vornehmlich zur Herstellung für Lehmbauplatten, wurde die mechanische Aktivierung mit einer Scheibenschwingmühle durchgeführt, um den Einfluss auf die Druck‐ und Biegezugfestigkeit zu untersuchen. Der verwendete Lehm wurde vorab gesiebt, die Fraktionen < 250 μm gemahlen und in unterschiedlichen Zusammensetzungen zu Prüfkörpern verpresst. Für Proben bestehend aus einer Mischung aus der gemahlenen Fraktion und größeren nicht gemahlenen Fraktionen konnte eine maximale Steigerung der Druckfestigkeit von 74 %, bei einer Mahldauer von 60 Minuten und 20 M.% Zugabe von Wasser festgestellt werden. Auch bei rheologischen Vortests (SAOS), bei welchen die Kohäsionsentwicklung der Probe, in Form einer Paste, über die Zeit gemessen wurde, wurde ein Maximum der Reaktionsfähigkeit bei 60 Minuten lang gemahlenen Proben erfasst. Eine Steigerung der Biegefestigkeit wurde nicht nachgewiesen.

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Über das Potenzial von calciniertem Ton in zementgebundenen Systemen

Cited by 7 publications

References 0 publications

A Mass Balance Approach for Thermogravimetric Analysis in Pozzolanic Reactivity R3 Test and Effect of Drying Methods

A Mass Balance Approach for Thermogravimetric Analysis in Pozzolanic Reactivity R3 Test and Effect of Drying Methods

Enhanced Metakaolin Reactivity in Blended Cement with Additional Calcium Hydroxide

Mechanische Aktivierung von Lehm

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