Abstract
ABSTRACT In this paper, an experimental program was carried out to investigate the residual mechanical properties of high strength concrete and normal strength concrete, and how moisture content and temperature affect the spalling process. Three mixtures with water-cementitious material ratios, from 0.25 to 0.50, and with different saturation levels were heated in an electric furnace to elevated temperatures, from 200°C to 600°C. After heating, the specimens were cooled down to room temperature and then tested for compression and tensile strength. The results showed that high moisture content induces the spalling process and reduces considerably the mechanical properties of high strength concrete, mainly at temperatures above 400°C.
Highlights
In recent years, the construction industry has shown significant interest in the use of High Strength Concrete (HSC), whereas it offers significant economic and architectural advantages over the Normal Strength Concrete (NSC), among being suited for special construction requiring high durability [1]
The results showed the cover loss of concrete due to spalling and the exposition of aggregates to fire. [18] reported that a lower w/b at the beginning of mixing and/or a higher moisture content at the time when concrete is exposed to high temperature is prone to induce spalling of concrete as a result of the increased pore vapor pressure
The effects of moisture content on the residual properties of different concrete grades exposed to high temperatures were investigated
Summary
The construction industry has shown significant interest in the use of High Strength Concrete (HSC), whereas it offers significant economic and architectural advantages over the Normal Strength Concrete (NSC), among being suited for special construction requiring high durability [1] These advances result from improvements in the material internal microstructure given by several factors, such as: modifications in the mixture composition, water-reduction admixtures, the use of superplasticizers, optimization of grain size distribution, the use of particles with pozzolanic activity, fibers addition, etc. The material explosively brakes into pieces, often without advance notice [5] This phenomenon is strongly related to the initial pore saturation and moisture migration in concrete. A review of the literature indicates that explosive spalling is a result of a combination of two effects: the build-up of pore pressure by vaporization and moisture transport and thermal stresses and external loads in concrete [3, 7,8,9,10]
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