"High-strength concrete (HSC) columns were found to be more prone to explosive spalling due
to their low permeability and high brittleness. Adding polypropylene fibers to the mix could be a solution since the
fibers melt during the early stages of heating and create channels in the concrete. Hence, the water vapor finds
an escape without causing spalling. Coating of concrete members with special mortars, e.g. perlite and vermiculite
rendering, could be another solution since the coating works as an insulation, which prevents heat from penetrating
to the heart of concrete. Previous researchers pointed out that the data on the effect of fire on the behavior
of HSC loaded columns is scarce. In addition, the authors did not cite any literature on the effect of cooling
regime on the fire behavior of HSC loaded columns. This paper presents an experimental program on the behavior
of HSC columns with or without polypropylene fibers and/or those coated with perlite or vermiculite mortar
under fire. The research includes testing seventeen reinforced HSC columns heated to 750°C for one hour under
three loading levels (30%, 40% and 50% of the control specimen’s ultimate load). To study the effect of cooling
regime, the columns were left to cool in air or quenched by water. The results indicated that a preload level, not
more than 40% of the columns’ ultimate load, leaving the column to gradually cool in air, inclusion of polypropylene
fibers and coating with perlite mortar greatly improved the residual capacity after fire. The column with the
above specification had a capacity almost identical to the control column, which was not heated." |
