DefinePK

Abstract

If a concrete structure is exposed to high temperature, inner structure of concrete degrades. Level of permeability of the surface layer is important for evaporation of water vapor from the whole bulk of the structure. If permeability of the surface layer is low, explosive spalling can occur and steel reinforcement can be uncovered. One of methods of measuring permeability of the surface layer of concrete is the Initial Surface Absorption Test (ISAT). The paper states results of experimental determination of permeability of the surface layer of concrete before and after thermal load. Tested concretes contained basalt aggregate and lightweight expanded clay aggregate. Results of the measurements showed that structure of surface layer in case of concrete with lightweight expanded clay aggregate is less porous than the structure of concrete with basalt aggregates. Damages caused by exposure to high temperature were recorded on both tested mixtures but concrete with lightweight expanded clay aggregate resists better.