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Aggregate Type Influence on Microstructural Behavior of Concrete Exposed to Elevated Temperature

100%

Belkadi A. A. , Kessal O. , Bensalem S. , Aggoun S. , Amouri C. , Khouadjia M. L. K.

Civil and Environmental Engineering Reports

2022

tom Vol. 32, no. 1

19--42

Exposure of concrete to high temperatures affects its mechanical properties by reducing the compressive strength, bending… etc. Factors reducing these properties have been focused on by several studies over the years, producing conflicting results. This article interested an important factor, that is the type of aggregates. For this, an experimental study on the behavior of concrete based on different types of aggregates: calcareous, siliceous and silico-calcareous subjected to high temperatures. In addition, the particle size distribution of the aggregates was chosen to be almost identical so that the latter does not affect the behavior of the concrete. Aggregates and concrete samples were subjected to a heating/cooling cycle of 300, 600 and 800°C at a speed of 1°C/ min. The mechanical and physical properties of concrete before and after exposure to high temperatures were studied. In addition, a microstructural study using a scanning electron microscope and a mercury porosimeter was performed. Thus, a comparative study between various researches on the mechanical properties of concrete exposed to high temperatures containing different types of aggregates was carried out. The compressive strength test results showed that the concrete based on siliceous aggregates (C-S) has better mechanical performance up to 300°C. However, above 300°C, the compressive strength decreases faster compared to calcareous-based concrete (C-C). According to the mercury porosimeter test, at 600°C, C-SC and C-S concretes have the highest number of pores compared to C-C concretes. The microstructure of concrete at high temperatures was influenced mainly by the aggregate’s types and the paste-aggregate transition zone. This study reinforces the importance of standardizing test procedures related to the properties of concrete in a fire situation so that all the results obtained are reproducible and applicable in other research.

Wielkość promienia kapilar o złożonej morfologii w aspekcie metody oznaczania

80%

Leżański J.

tom R. 45, nr 10-11

570-573

Przedstawiono wyniki badań nad opracowaniem metodyki oznaczania wielkości promienia kapilar w porowatych materiałach formowanych z proszków, odznaczających się złożoną morfologią i zróżnicowaną wielkością. Przedstawiono metodykę i przeprowadzono oznaczanie wielkości promienia kapilar za pomocą porozymetru rtęciowego oraz na podstawie pomiarów wielkości powierzchni właściwej porowatych kształtek. Stwierdzono dużą przydatność metodyki oznaczania promienia kapilar na podstawie powierzchni właściwej porowatego materiału.

The paper presents results of investigation of the method for determination of the size of capillary-radius in powder formed porous materials of composite morphology and diversified size. The method and results of determination of the size of capillaries by means of mercury-porosimeter and measurement of the size of the specific surface of the porous moulders are presented. The method of determination of the capillary-radius, on the ground of specific surface of the porous material, has been stated to be of great serviceableness.