Heat effect on the shielding and strength properties of some local concretes

The effect of heat on strength and on gamma-ray and neutron shielding properties of four types of the local concretes (denoted as H-mix, F-mix, D-mix and S-mix) were investigated, the samples were exposed to temperatures between 20 and 800 degrees C. Small losses in attenuation coefficients for gamma-rays and neutrons were observed for the studied types of concretes at 100 degrees C, while there were no changes in strength for H-mix and F-mix compared to 10- 15% loss of strength (the ratio of decreased compressive strength after exposure to heat to the original one) in D-mix and S-mix. No significant loss in attenuation has been noticed between 100 and 400 degrees C while unexpected increases in strength in some samples have been observed. No changes between 400 and 500 degrees C in gamma-rays attenuation except for D-mix which suffers a high loss in gamma-rays attenuation. The neutron attenuation decreases for the studied types at these temperatures, while the strength increases except for D-mix. F-mix and D-mix lost their integrities (destroyed) between 500 and 550 degrees C and losses in attenuation and increase in strength for the other two types. S-mix concrete lost 50% of its strength at 550 degrees C, while H-mix concrete lost 50% of its strength at 650 degrees C. It can be concluded that the H-mix which contains hematite aggregates have the best attenuation coefficients for both gamma-rays and neutrons and the best resistant for high temperatures effects. (C) 2007 Elsevier Ltd. All fights reserved.