Analysis of the thermomechanical behavior of different concretes with vermiculite and submitted to elevated temperatures

Abstract

At high temperatures, concrete may exhibit adverse mechanical behavior that compromises the safety of structures. Thus, it is necessary to study and develop concrete that can obtain greater performance in situations of exposure to high temperatures. In this regard, the present study investigates the replacement of 25% of sand by expanded vermiculite in different types of concrete and its performance when subjected to room temperature and punctual temperatures, of little content in literature, such as 200°C, 400°C and 800°C. This study also innovates by proposing the evaluation of prototypes exposed to high temperatures exclusively according to the perspectives of Brazilian technical standards, without resorting to international guidelines. Thus, the consistencies of the mixtures were determined and analyzed, as well as physical and mechanical tests that were carried out with the produced concrete. Among the results found are: vermiculite reduces the workability of the concrete mixture; vermiculite is not recommended for high-performance concrete, as it can significantly reduce its mechanical properties; in general terms, concrete that has a design strength of 50 MPa benefits from replacing the fines aggregate with vermiculite. From 400°C of exposure, all of the concrete samples showed cracks. The spalling phenomenon was also noticed in some specimens. The developed concrete samples cannot be characterized as lightweight concrete according to Brazilian standards, but o can be recommended as structural concrete given that their apparent specific mass is greater than 2000 kg/m³.

Keywords:
concrete; light concrete; expanded vermiculite; vermiculite; thermomechanical properties; high temperature.