Strain of heated concrete during two thermal cycles. Part 1: strain over two cycles, during first heating and at subsequent constant temperature

This paper presents the strain behaviour of three nuclear reactor type plain unsealed (50–60 N/mm2) concretes exposed under 0% and 20% compressive loads to a 14-day two-thermal-cycle test (test temperatures ranging from 100°C to 600°C). A generic approach is taken for wider application and for the in-depth understanding of the behaviour of heated concrete in general. Concrete during the two thermal cycles experiences both expansive and contractive strains. The former includes ‘thermal expansion’, cracking expansion and chemically induced expansion. The latter includes drying shrinkage, load-induced thermal strain (LITS) during virgin heating, ‘delayed’ LITS at constant temperature and time-dependent creep. The overall strains during heating, at constant temperature and during cooling reflect both contractive and expansive influences. LITS is absent during cooling and a second heat cycle. A summary of the influences of material and environmental factors upon the thermal strain and LITS of concrete is given...

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