Alina Kliszczewicz

INFLUENCE OF RECYCLED AGGREGATES ON MECHANICAL PROPERTIES OF HS/HPC

Abstract Recently, aggregates derived from demolished concrete structures were of relatively low strength, and applications were of secondary importance. Since a short time, the necessity of demolition of structures with strong concrete, like building frames or bridge beams, has appeared and created the source of recycled aggregate of quite new generation. Besides of obvious environmental aims recycling of concrete has gained new economical aspects. Concrete in responsible structures, with strength of 40–70 MPa for instance, was originally mixed from aggregate of good quality, e.g. granite or basalt, and with large amount of cement. The aggregate obtained from crushing of such structures retained some binding abilities as may be activated by means of silica fume or fly ash admixtures. Generally, such aggregates are different from natural and, consequently, concrete made with use of them has specific properties. The results of research on mechanical properties of structural recycled high performance concrete (RHPC) are presented.

Differences in instantaneous deformability of HS/HPC according to the kind of coarse aggregate

In the analysis of concrete structures the knowledge of real values of modulus of elasticity is of great importance, particularly at displacements or losses of prestressing consideration. For two-dimensional problems the Poissons ratio is important too. Recommendations from the Standards can inform us roughly about these values but usually in the range of classes of ordinary concrete only. In general, greater the strength of concrete greater the differences in modules of elasticity for similar classes of concrete are. In the first row material factors have to be taken into consideration. To explain the range of variations the results of tests for high-strength/high-performance concrete manufactured with different components, particularly various kinds of coarse aggregates are presented. These results are compared with some other tests and with basic recommendations.