Relation between ultrasound measurements and phase evolution in accelerated cementitious matrices

Abstract

This paper focuses on the characterization of setting and hardening of accelerated cementitious matrices by ultrasound propagation velocity, correlating these processes with chemical parameters and the phase evolution obtained by in situ XRD. Evolution of temperature and determination of setting times complemented this analysis. The technique employed provided a continuous monitoring of the setting and hardening of the hydrating matrix and was susceptible to changes in accelerator reactivity and phase composition. Results showed that ettringite formed by accelerator reaction improves the solid-phase interconnectivity and increases initial ultrasound velocity. P-wave propagation during the acceleration period is directly proportional to alite and C3A degrees of hydration. The influence of AFm phases to increase ultrasound velocity is stronger than ettringite and C-S-H. Based on an extensive statistical analysis, multivariate linear regressions were established between ultrasound velocity and the main chemical properties influencing its evolution, leading to a better comprehension of how these parameters are related.Peer ReviewedPostprint (author's final draft

Effects of Vehicle-Induced Vibrations on the Tensile Performance of Early-Age PVA-ECC

“…This would probably make the water-cement ratio around the interface of the fibers/matrix larger than that of other parts of the matrix, and this then would cause bond reduction for the interface of the fibers/matrix. Furthermore, a large number of ettringite (AFt) precipitates will have formed in the matrix at this stage [23], sufficient free water will make it more conducive to hydroscopic expansion of the AFt at the interface of the fiber/matrix [24], resulting in a larger porosity at the fiber/matrix interface, which would cause further bond reduction for the fibers/matrix interface.…”

Effects of Vehicle-Induced Vibrations on the Tensile Performance of Early Age PVA-ECC

“…This would probably make the water-cement ratio around the interface of the interface of the fibers/matrix larger than that of other parts of the matrix, and then causes bond reduction for the interface of the fibers/matrix. Furthermore, a large number of ettringite (AFt) precipitates will have formed in the matrix at this stage [23], sufficient free water will make it more conducive to the hydroscopic expansion of the AFt at the interface of the fiber/matrix [24], resulting in a larger porosity at the fiber/matrix interface, which would cause further bond reduction for the fibers/matrix interface.…”

Estudio de las reacciones de hidratación temprana en el hormigón proyectado

“…Existen algunos estudios centrados en las reacciones que ocurren durante la hidratación de sistemas acelerados [1][2][3][4][5]. En todos los casos la presencia del acelerador modifica las condiciones de hidratación, dependiendo los productos de hidratación que se forman del tipo y de la cantidad de acelerador que se utilice.…”

“…Precisamente por la diferente naturaleza de los productos de hidratación, los aceleradores también determinan el desarrollo del fraguado. En el caso de aceleradores sin álcalis basados en sulfato de aluminio, según Paglia y col. [1], la cristalización de ettringita prismática entre los granos de clinker da lugar a una masa compacta, acelerando así el fraguado; por el contrario, en sistemas acelerados con aditivos ricos en álcalis KAl(OH) 4 , el rápido fraguado se atribuye a la precipitación de placas de portlandita e hidratos amorfos (KCASSH). La concentración de aluminio y sulfato del acelerador, así como la cantidad y el tipo de regulador de fraguado en el cemento, controlan la reactividad de los aceleradores en los diferentes sistemas [2].…”

“…Estudio de las reacciones de hidratación temprana en el hormigón proyectado I. Galan (1) , A. Stauffacher (2) , F. Mittermayr (2) , M. Thumann (3) , W. Kusterle (3) , P. Juilland (4) , C. Stenger (4) y B. Lindlar (…”