Abstract
The results of compressive fatigue investigations on four high-strength concretes and their corresponding mortars are presented. The influences of coarse aggregates generally, the substitution of basalt coarse aggregate by granite, the addition of silica fume and the variation of the water to cement (w/c) ratio are investigated systematically. The numbers of cycles to failure, the developments of strain, stiffness, dissipated energy and acoustic emission hits are focused on in the analyses. The results clearly show that coarse aggregates can influence the fatigue behaviour of concretes in a negative way at higher stress levels and in a positive way at lower stress levels compared to mortars. The granite coarse aggregate decreases the adverse effect at higher stress levels due to its lower modulus of elasticity compared to that of the basalt aggregate. Silica fume improves the fatigue behaviour of concrete and mortar strongly. The increase of the w/c ratio and, thus, the increase in porosity reduces the fatigue resistance of concrete and mortar significantly, due to the weakening of the mortar matrix and of the interfacial transition zone. The results demonstrate the interaction of the coarse aggregates and the mortar matrix with their specific properties, which leads to a certain fatigue behaviour. The acoustic emission gives additional valuable strain-independent information of the damage processes occurring, possibly also on micro- and nanoscales.
Highlights
Concrete compositions with ever-higher compressive strengths enable the realisation of more filigree concrete structures
It is well-known that high-strength concrete has a denser binder matrix with increased compressive strength and improved interfacial transition zones (ITZ) compared to normal-strength concrete
High-strength concrete shows a longer second phase of the strain development compared to normal-strength concrete [1, 4, 9–11]
Summary
Concrete compositions with ever-higher compressive strengths enable the realisation of more filigree concrete structures These structures are exposed to fatigue-relevant loads to a higher extent because of their lower ratio of deadweight to non-static loads. [1–3]), using damage indicators such as strain, stiffness or dissipated energy It is well-known that high-strength concrete has a denser binder matrix with increased compressive strength and improved interfacial transition zones (ITZ) compared to normal-strength concrete. This leads to an increased modulus of elasticity. Some investigators found that high-strength concrete has a lower fatigue resistance compared to normal-strength concrete High-strength concrete shows a longer second phase of the strain development compared to normal-strength concrete [1, 4, 9–11]
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