Incorporating reinforcement into the practice of digital concrete construction, often called 3D-concrete-printing, is a prerequisite for wide-ranging, structural applications of this new technology. Strain-Hardening Cement-based Composites (SHCC) offer one possible solution to this challenge. In this work, printable SHCC were developed and tested. The composites could be extruded through a nozzle of a 3D-printer so that continuous filaments could be deposited, one upon the other, to build lab-scaled wall specimens without noticeable deformation of the bottom layers. The specimens extracted from the printed walls exhibited multiple fine cracks and pronounced strain-hardening characteristics under uniaxial tensile loading, even for fiber volume fractions as low as 1.0%. In fact, the strain-hardening characteristics of printed specimens were superior to those of mold-cast SHCC specimens.

Tensile fracture of fiber reinforced cement-based composites (FRCC) with rebar was investigated via a mesoscale analysis using discretized short fibers. Herein, the effects of fiber volume fraction, steel reinforcement ratio, FRCC–rebar bond characteristics, and fiber distribution on tensile fracture behavior were investigated. In some cases, localized crack was observed in the post-yield range of rebar. The localization mechanism was numerically explained and then inhibited by focusing on the bridging forces of the fibers and rebar. The effectiveness of steel reinforcement in enhancing the strain capacity of strain-hardening cement-based composites was confirmed. This paper is based on an original paper (Ogura et al. 2016) written in Japanese.

This paper presents flexural analysis of PET (PolyEthylene Terephthalate) fiber reinforced concrete using 3-D meso-scale analysis to verify reinforcement mechanisms in PET fiber. In this proposed model, fibers with a specific length and diameter are distributed as discrete entities within a specimen. In this work, it has been clarified that the proposed model can adequately simulate load- displacement relations obtained from flexural tests of PET fiber reinforced concrete. This paper also presents numerically investigations in order to assess the effects of fiber length and strength on flexural toughness.