Use of ammonium nitrate solution to simulate and accelerate the leaching of cement pastes due to deionized water

Abstract

Studies in the laboratory on the durability of concrete are not easy to perform, particularly in the case of a linkage between a chemical attack and a mechanical property variation. As a result, these studies require significant experimentation times because on the one hand the kinetics ofchemical degradation are very slow, and on the other hand the sample size has to be adapted to the aggregate size. One of the possibilities for solving these problems consists of developing accelerated tests allowing one to reproduce the real degradation undergone by the concrete during its history. This paper deals with the use of strongly concentrated ammonium nitrate solutions as an accelerated method for the degradation of cement-based materials by deionized water. The direct application of this work is to the durability of concrete containers used to store radioactive wastes.

Performance of carbon nanofiber-cement composites subjected to accelerated decalcification

“…Decalcification of cement paste by NH 4 NO 3 has been shown to be similar to decalcification by water [9][10][11]. Both leaching processes yield the dissolution of calcium hydroxide (CH) followed by the decalcification of the C-S-H phases [9], but the NH 4 NO 3 solution provides an accelerated decalcification (by approximately two orders of magnitude [10]) due to the increased equilibrium calcium solubility of the NH 4 NO 3 solution over that of pure water [11].…”

Estudio del proceso de descalcificación en morteros degradados en NH₄NO₃ empleando técnicas ultrasónicas

“…If we consider an ultrasonic inspection in a uniformly degraded degradada, mediante un experimento de transmisión ultrasónica (como el representado en la Figura 11a), podemos asumir idealmente una zona externa degradada (D) con un espesor X D y una zona interna no degradada (U) con un espesor X U . En esta situación teórica, encontraríamos que el perfil de velocidades ultrasónicas sería una función en escalón que depende del espesor X B del haz ultrasónico (B), de los espesores y de las velocidades ultrasónicas en la zona degradada (V D ) y no degradada (V U ), de tal modo que la velocidad máxima V M y la velocidad mínima V m pueden expresarse por las ecuaciones [3] y [4]:…”

“…When making the ultrasonic experiment, the ideal ultrasonic velocity profile will be a step function which depends on: the thickness X B of the ultrasonic beam (B), the thickness and ultrasonic velocity in the degraded (V D ) and non-degraded zone (V U ). According to this the maximum V M and minimum V m ultrasonic velocity can be expressed by equations [3] and [4]:…”

“…En las últimas décadas la caracterización de los procesos de descalcificación se ha abordado mediante ensayos acelerados (3)(4)(5)(6), al ser procesos muy lentos, y así poder proporcionar estimaciones de la vida útil de estos materiales. Gran parte del esfuerzo se ha puesto en desarrollar modelos de vida útil con los resultados…”

“…In the last decades, characterization of decalcification processes has been tackled by accelerated ageing tests (3)(4)(5)(6) as calcium leaching is a relatively slow process. Accelerating degradation can give us an useful estimation of the expected life-time of cement-based materials provided that the process does not introduce factors influencing obtenidos (7)(8)(9).…”