Residual mechanical properties of hollow concrete blocks with different aggregate types after exposure to high temperatures

Abstract

The exposure of concrete to high temperatures negatively affects its mechanical properties, and the factors that reduce these properties have been the subject of several studies over the years. Nevertheless, there are few studies on concrete for manufacturing blocks for structural masonry of very dry and vibro-pressed consistency. This paper shows the results of an experimental study on the mechanical strength and residual deformability modulus of hollow concrete blocks when exposed to temperatures from 100 to 800 °C. Three types of coarse aggregates—basalt, gneiss, and calcareous—were used, also varying the resistance of the inspected blocks − 12 MPa, 24 MPa, and 48 MPa. The differences in thermal and mechanical properties between concrete produced from a fluid mixture formed and consolidated in a mold, and concrete made of blocks for load-bearing masonry of very dry consistency and vibro-pressed are highlighted. The results also confirmed the low-level influence of compressive strength on the evolution of residual mechanical strength and the strong influence of the type of aggregate on this behavior. It was also found that the evaluation of residual thermal and mechanical properties of a wet-shaped concrete mixture to represent the behavior of dry and vibrated concrete, used in the manufacture of blocks for load-bearing masonry, can lead to unrepresentative results. There is no precedent for a study conducted with these parameters for this purpose that has applied such international recommendations.