Análisis experimental de hormigones Análisis experimental de hormigones expuestos al fuego

Abstract

Conventional thermogravimetric analysis requires small sample

volumes to perform the experiments and, in the case of concrete, it

is very diffi cult to take into account the effects of aggregates and

moisture migration during tests. In the present work, an experimental

methodology inspired in thermogravimetric methods was developed.

The methodology proposed permits to assess the behaviour of small

concrete samples exposed to a fast unidirectional heating, taking

into account the effects of aggregates and moisture. For validation

purposes, three types of normal strength concretes under two different

heat exposures have been analyzed. Cylindrical concrete samples

of 150 x 300 mm were cast. After curing cylindrical cores of 95

millimetres in diameter were extracted and shaped to 48 ± 2 mm

in height. The samples were exposed to a two different heat fl uxes

(35kW/m2 and 75kW/m2) for 30 or 60 minutes. Mass loss rate and

temperatures were measured every 1 second. Additionally, the heat

transfer process was also monitored using infrared thermography.

Experimental results shows that the methodology proposed is suitable

to evaluate different hydro-thermal processes that take place in

concrete exposed to fi re as the free water release, decomposition of

calcium silicate hydrated and the decomposition of Porlandite. Initial

moisture content of concrete plays a direct infl uence en mass loss rate

at high exposure condition. No signifi cant differences were observed

at the lower heat fl ux. At the same exposure conditions, samples with

lower moisture content shows lower mass loss rate.