This thesis presents the results of the experimental study carried out for considering the
effects of the type, size and amount of coarse aggregate on the behavior of normal and high
strength concretes, and on relationship among the fracture energy and typical mechanical strength
of concrete. The experimental concrete mixtures were made with basalt and granite coarse
aggregates having maximum size particle 9.5 mm e 19 mm and volumetrically fraction in the
mixture ranging from 0.65 to 0.75. The water to cementation materiais ratio ranged from 0.35 to
0.50. The high strength concrete mixtures contained a fixed amount of 10 percent of silica fume
in relation to the weight Portland cement used and a proper addition of superplasticizing agent.
Sixteen (16) concrete batching, and one hundred and ninety two tests were carried out to measure
the mechanical resistance of concrete (compressive strength, flexure strength, spittling tensile
strength, modulus of elasticity) and fracture energy. The fracture properties measured in
agreement of the RILEM test methods. The concrete compressive strength ranged from 40 to 60
MPa, and from 70 to 110 MPa, for moderate and high strength concretes, respectively, depending
on the type of coarse aggregate utilized. The results showed that the concrete resistance
(compressive, flexure, spittling tensile) and fracture energy, at given water to binder ratio, depend
on type, particle dimension and content of coarse aggregate. The characteristic length of
Hülerborg^ fictitions cracks model increases with the variation in the particle dimension of
coarse aggregate.
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