Transverse isotropic compression behavior of aligned steel fiber UHPC produced by electromagnetic field

Abstract

Aligned steel fiber ultra-high performance concrete (ASF-UHPC) demonstrates transverse isotropic mechanical properties. Specifically, when subjected to compressive stress perpendicular to the fiber orientation, surface cracks emerge proximate to the fiber tips, resulting in a significant enhancement of the material's compressive strength. Conversely, under compressive stress applied parallel to the fiber direction, fissures manifest along the fiber orientation, leading to a notable reduction in compressive strength. Consequently, the primary contributory factor underlying augmented compressive strength is the lateral restraint effectuated by the fibers. The optimization of fiber distribution for the aim of altering compressive strength is subject to the influence of the qualities of the UHPC matrix. Moreover, a comprehensive analysis extends to the examination of pertinent parameters, encompassing fiber volume fractions, fiber lengths, and fiber shapes. Investigation of these facets reveals an optimal range of fiber volume fraction, approximately 1.0% to 1.5%, which imparts maximal compressive strength in ASF-UHPC subjected to compressive stress perpendicular to the fiber orientation. When forces are applied parallel to the fiber direction, the incorporation of longer fibers or hooked-end fibers mitigates the reduction in compressive strength perpendicular to the applied stress. The consideration of the transverse mechanical attributes exhibited by aligned steel fibers, coupled with the optimization of fiber distribution characteristics, not only attenuates steel fiber consumption but also underscores a sustainable approach by curtailing CO2 emissions.