Kinetic and thermodynamic study in pozzolanic chemical systems as an alternative for chapelle test
Marco César Prado Soares, Beatriz Ferreira Mendes, Egont Alexandre Schenkel, Murilo Ferreira Santos, Eric Fujiwara, Carlos Kenichi Suzuki
ARTIGO
Inglês
Agradecimentos: The authors would like to thank Brazilian Nanotechnology National Laboratory LNNano) for the use of the facilities, CNPq, CAPES, and FAPESP Grants 2015/02185-3 and 2017/20445-8 for financial support
Important properties in cementitious materials, such as concrete, are related to the presence of additives that influence the rigidity and the physical and chemical resistances. For the evaluation of the additive effectiveness, known as pozzolanic activity, a simple procedure, the Chapelle test, is...
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Important properties in cementitious materials, such as concrete, are related to the presence of additives that influence the rigidity and the physical and chemical resistances. For the evaluation of the additive effectiveness, known as pozzolanic activity, a simple procedure, the Chapelle test, is commonly used, and it essentially consists in a reaction between the additive with calcium oxide in aqueous medium. However, such procedure presents limitations in terms of processing time and lack of information regarding the reactions kinetics. In this sense, a simple method based on the kinetic and thermodynamic principles of chemical reactions is proposed, which can be performed using conventional electronic pH sensors. The study provides an alternative methodology with many advantages over the traditional procedure, such as energy and time-savings, more robustness and more confidence. In this paper, three types of silica nanoparticles that can be used as low-cost additives were characterized in relation to their morphology and crystallinity by XRD and SEM, the particles average diameters were obtained and the particles were used for studying the chemical process that takes place during the Chapelle test. Results and the semi-empirical analysis provided strong evidence that the process is an acid-base 1:1 reaction and it was verified that the mean reaction times varied from 64 to 195 min. It is a remarkable result, since the proposed analysis can be performed with simple, fast and low-cost instrumentation and needs only a worksheet software, whereas the Chapelle test takes 16 hours and provides no dynamic information. Besides the limitation that the methodology is not able to quantify and to elucidate the effects of the specific surface area of the particles, which needs a complete BET study, the research provides a significant contribution for the understanding of the pozzolanic process, of great importance in both concrete and ceramic research.
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CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQ
COORDENAÇÃO DE APERFEIÇOAMENTO DE PESSOAL DE NÍVEL SUPERIOR - CAPES
FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPESP
2015/02185-3; 2017/20445-8
Aberto
Kinetic and thermodynamic study in pozzolanic chemical systems as an alternative for chapelle test
Marco César Prado Soares, Beatriz Ferreira Mendes, Egont Alexandre Schenkel, Murilo Ferreira Santos, Eric Fujiwara, Carlos Kenichi Suzuki
Kinetic and thermodynamic study in pozzolanic chemical systems as an alternative for chapelle test
Marco César Prado Soares, Beatriz Ferreira Mendes, Egont Alexandre Schenkel, Murilo Ferreira Santos, Eric Fujiwara, Carlos Kenichi Suzuki
Fontes
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Materials research Vol. 21, no. 4 (June, 2018), n. art. e20180131 |