| Abstract: |
High strength concrete is a relatively’ new material that meetsspecial performance and uniformity requirements. So, an extendedcomprehensive knowledge of the fundamental properties of high strengthconcrete is necessary. The mechanical properties and fracture behaviorare among those fundamental properties. The principle of the fracturemechanics theory have important practical implication in the selectionand design of high strength concrete.In this work, an experimental program was designed to investigatethe mechanical properties of concrete mixes having different concretestrengths. The compressive strength of concrete mixes were, 32.5, 52.5,62, 87 and 98 MPa, which give the two levels of normal and highcompressive strength. The behavior of indirect tensile strength, flexuralstrength and modulus of elasticity under compression were analysid inthis study. The relations between these properties in high strengthconcrete are compared to those in normal strength concrete.For each concrete compressive strength the fracture behavior ofedge-notched beam was determined in three-point loading conditions.The beam length to depth ratio Lld was constant and equals to 4. Foursizes, d = 80, 120, 150 and 240 mm were considered. The crack length todepth ratio, aid, were equal 0.1, 0.2, 0.3 and 0.4. The fracture parameterswere determined using linear elastic fracture machine and size effectlow. The critical stress intensity factor determined from LEFM wasmodified to take into consideration the effect of beam size, crack length,and maximum aggregate size of coarse aggregate. The proposed fracturemodel was used to correlate the effect of specimen size and notch depth
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