Kinetic and Thermodynamic Study in Pozzolanic Chemical Systems as an Alternative for Chapelle Test

AUTOR(ES)

Soares, Marco César Prado, Mendes, Beatriz Ferreira, Schenkel, Egont Alexandre, Santos, Murilo Ferreira, Fujiwara, Eric, Suzuki, Carlos Kenichi

FONTE

Mat. Res.

DATA DE PUBLICAÇÃO

25/06/2018

RESUMO

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.

Documentos Relacionados

• Porphyrin test as an alternative to benzidine test for detecting cytochromes in catalase-negative gram-positive cocci.
• An assessment of Sickledex as an alternative to the sickling test.
• Glucagon test for insulinoma: a chemical study in 25 cases
• Thermodynamic and kinetic properties of short RNA helices: the oligomer sequence AnGCUn
• Enzyme-linked immunosorbent assay-based inhibition test for neutralizing antibodies to polioviruses as an alternative to the neutralization test in tissue culture.