Carbonate aggregate in concrete exposed to high temperatures

The paper presents the experimental campaign on the problem of post-fire rehydration of carbonate aggregates, resulting in expansion and fall of the treated layer at high temperature.In the experimental campaign, three types of aggregates (2-8 and 8-16 mm grain size) are used for the production of concrete specimens: (1) the thermally stable representative of igneous rocks -basalt and two representatives of sedimentary carbonate rocks: (2) dolomite (with 1% calcium carbonate at 20 C and 25% of calcium carbonate after heating > 500C) and ( 3) limestone (with 98% calcium carbonate).The 150 mm cubic samples were heated in an electric furnace at 1 C/min to the set temperature (200 C, 600 C, 1000 C).After heating, the following measurements were compared: mass and density (directly after cooling), compressive strength (after 14 days), and crack development and height of the samples were monitored for 6 days, followed by heating (144 hours).As a result of heating to a temperature of 1000C, a sharp decrease in concrete mass and an increase in the cross-sectional height of the specimen are observed in concrete with carbonate aggregate.This results in a large reduction in bulk density and compressive strength and in the disintegration of samples containing carbonate aggregate in the days following heating.This peculiarity of carbonate aggregate has already been studied in the literature.Carbonate aggregates have a convincing property as an aggregate used daily in construction.However, these properties deteriorate significantly in the event of fire and more effort needs to be made to disseminate this knowledge.