Pozzolanic activity of metakaolins by the French standard of the modified Chapelle test: A direct methology

Abstract

This research was focused on the use of the modified Chapelle test as a direct laboratory methodology to access the pozzolanic activity of both experimental and commercial metakaolins. At the same time, this test was used in the evaluation of experimental metakaolins. This chemical test, performed during 16 hours at 90 °C, allows the quantification of portlandite fixed by the metakaolin sample. The calcium hydroxide that was not consumed is quantified by acid titration (HCl), and the test result is expressed in mg of fixed calcium hydroxide by g of metakaolin. According to this test, the pozzolanic activity of a metakaolin should not be less than 700 mg Ca(OH) 2 / g metakaolin. The modified Chapelle pozzolanic activity of six commercial metakaolins was evaluated between 920 and 1560 mg Ca(OH) 2 / g metakaolin. From the seven experimental metakaolins produced between 750 ºC and 940 ºC, a material with modified Chapelle pozzolanic activity value of 1240 mg Ca(OH) 2 / g metakaolin was obtained, which is similar to some tested commercial metakaolins produced at industrial scale. The metakaolin produced at 800 ºC was ground, resulting in a particle size reduction of ≈ 4x less and a consequent increase of 21 % in the pozzolanic activity.

Pozzolanic activity of kaolins containing aluminum hydroxide

“…Thus, 10 wt% of AH 3 was added to K and Kc to obtain powders labelled as K 10 and Kc 10 respectively. The pozzolanic activity of K, Kc, K 10 and Kc 10 was assessed by the modified Chapelle test according to NF P 18–513 Standard 18 which is based on the definition of pozzolanic material as the one capable of binding to portlandite (Ca(OH) 2 ) in aqueous solution. For this text, 2 g of CaO were mixed with 1 g of each material (K, Kc, K 10 and Kc 10 ) respectively in 250 mL of distilled CO 2 -free water to form solutions of hydrated lime or portlandite.…”

“…From the filtrate, the remaining unreacted portlandite was extracted with saccharose and titrated by a 0.1 N hydrochloric acid solution according to equation (Eq. 1) 18 , 19 , each value considered being the average of three test results made under the same conditions. On the other hand, the precipitated products of reactions with K, Kc, K 10 and Kc 10 , denoted as K′, Kc′, K 10 ′ and Kc 10 ′ respectively, were analyzed by XRD to identify constitutive phases.…”

“…On the other hand, the precipitated products of reactions with K, Kc, K 10 and Kc 10 , denoted as K′, Kc′, K 10 ′ and Kc 10 ′ respectively, were analyzed by XRD to identify constitutive phases. A blank experiment was carried out similarly without the materials under study for comparison 18 . …”

Applying Chemometrics to Evaluate Tungsten Mining Residues Potential As Partial Cement Replacement

“…The present work aimed to study the pozzolanic reactivity by the total amount of Ca(OH) 2 consumed in Chapelle test [12] by tungsten mining residues from Panasqueira mine after being subjected to electroremediation with NADES. The thermal treatment was also coupled with the electrodialytic process (ED) to enhance residues pozzolanicity.…”

Metakaolin test for the chemically bound water

“…Методики определения индекса активности известны и хорошо описаны в литературе [16][17][18][19], а сведения о методах определения химически связанной воды в метакаолине немногочисленны.…”