Mechanical behaviour of strain-hardening cement-based composites (shccunder low and high tensile strain rates)

In this research project the behaviour of strain-hardening, cement-based composites (SHCC subjected to low and high strain rates was studied. Uniaxial tension tests on dumbbellshaped SHCC specimens were performed at rates ranging from 0.00001s-1 to 50s-1. For the tests performed at strain rates of 0.01s-1 and below, SHCC yielded a moderate increase in tensile strength and simultaneous decrease in strain capacity with increasing strain rate. When tested for higher strain rates from 10 to 50s-1 a considerable increase in tensile strain and strain capacity was measured. Microscopic investigation of the fracture surfaces provided some insight into the specific mechanisms of SHCC failure under high rates of loading. In contrast to rapid quasi-static testing (=0.001s-1 where an average fibre pullout length of 0.3mm was observed, almost no fibre failure and an average pullout length of approximately 2.5mm were found in the high strain rate tests (25s-1. Furthermore, the fibres on the fracture surfaces produced in the high rate tests exhibited pronounced plastic deformations.