Abstract
The paper presents a part of an experimental campaign consisting of quasi-static and impact tensile experiments on three different types of strain-hardening cement-based composites (SHCC) as well as on their constitutive cementitious matrices [1]. The investigation on different SHCC types was intended for analysing the effect of matrix composition and fibre type on the strain rate sensitivity of the composites and for enabling the formulation of material design recommendations for impact resistant SHCC. The dynamic tests were carried out by means of a Modified Hopkinson Bar (MHB) installed in the DynaMat Laboratory in Lugano, Switzerland, which enabled the characterization of the dynamic material behaviour under direct tensile loading in terms of force-displacement relationships.
Highlights
The vast majority of the civil constructions are made of reinforced concrete (RC)
The first-crack stress of M1-PVA is in average the highest among the three tested types of strain-hardening cement-based composites (SHCC). This is a result of the strong chemical bond between the PVA fibres and the cementitious matrix, which involves the fibres in hindering the propagation of micro-cracks already before steady-state cracking as indicated by the first stress drop in the stressstrain curve
The hydrophobicity of the high-density polyethylene (HDPE) fibres leads to a weak frictional bond with the normal-strength cementitious matrix M1 meaning that the fibres are activated mainly after crack formation
Summary
The vast majority of the civil constructions are made of reinforced concrete (RC). Due to the low tensile strength and pronounced brittleness of concrete, RC structures feature a relatively low resistance against various types of dynamic loading, such as caused by earthquake, impact or blast. The performance of existing RC structures under dynamic loading can be enhanced by applying strengthening layers Their function is to increase load bearing capacity, stability and to ensure a strong confinement of the concrete core. With regard to dynamic loading, the structural elements should permit considerable inelastic deformations and ensure energy dissipation without losing load bearing capacity In this sense strain-hardening cement-based composites (SHCC) represent a promising solution [4]. The composites exhibit a strain-hardening tensile behaviour associated with a pronounced multiple cracking before failure localization Owing to their sufficiently high tensile and compressive strength, high ductility and remarkable crack control, SHCC can enhance the load bearing capacity, damage tolerance and durability of structures, both if used in strengthening layers [5,6,7,8] or as main. The detailed report was published in [1]
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