In the dry storage of spent nuclear fuels

concrete cask serves both as a shielding and a structural containment.The concrete in the storage facility is expected to endure the decay heat of the spent nuclear fuel during its service life.Thus

effects of the sustaining high temperature on concrete material need be evaluated for safety of the dry storage facility.In this paper

we report an experimental program aimed at investigating possible high temperature effects on properties of concrete

with emphasis on the mechanical stability

porosity

and crack-resisting ability of concrete mixes prepared using various amounts of Portland cement

fly ash

and blast furnace slag.The experimental results obtained from concrete specimens exposed to a temperature of 94oC for 90 days indicate that:(1) compressive strength of the concrete remains practically unchanged;(2) the ultrasonic pulse velocity

and dynamic modulus of elasticity of the concrete decrease in early stage of the high-temperature exposure

and gradually become stable with continuing exposure;(3) shrinkage of concrete mixes exhibits an increase in early stage of the exposure and does not decrease further with time;(4) concrete mixes containing pozzolanic materials

including fly ash and blast furnace slag

show better temperature-resisting characteristics than those using only Portland cement.