It is rare to see concrete structures damaged by some impact load in practice and there is few structures of which impact load is considered as a main external force in the design. In this report, feature of impact phenomenon of concrete structures, material properties such as compression stress and stress-strain relationship under high strain rate and structural response and design method against impact load were described.
A new method for the recycle of sludge generated at ready-mixed concrete plant has been reported at present. This method is able to apply sludge water by adding a retarder for mixing water, without the amendment of mix proportion of concrete due to the use of sludge water, within 3% of sludge content by cement weight Since ready mixed concrete made by this method was applied for a building construction, the property of sludge water added retarder and the quality of concrete used in the construction are described in this paper.
Concrete waste has been recycled mainly for roadbeds and backfill, but high quality products must be indispensable for increasing its recycling application. From this point of view, production techniques on high quality recycled aggregate from concrete waste generated during dismantling of nuclear power plants have been developed. Small scale testing on the mechanical grinding method and the heating and grinding method have evaluated performance on recycled aggregates, recycled concrete using the recycled aggregates, and real scale wall model. The result shows that recycled aggregate achieved such high quality as ordinary aggregate.