Combining 3D textiles and synthetic microfibers for a sustainable strain-hardening behavior in cementitious materials

Abstract

Concrete and traditional cement have a significant environmental impact. As they will continue to be used abundantly, solutions are necessary to ensure a more sustainable application. The use of metallic reinforcements in cementitious material leads to environmental and durability concerns as well, such as corrosion. A new way of reinforcing cementitious materials is combining 3D textiles with synthetic microfibers. This reinforcement combination, with naturally higher corrosion resistance, can lead to slender, lighter, and more durable structures. The 3D textiles guarantee the loadbearing capacity while the synthetic microfibers limit the crack widths to an acceptable range in which the cracks can be healed through the autogenous healing of the cementitious material. This limits the necessity for maintenance and repair works, increasing the service life of future civil works. Synthetic microfibers, 3D textiles and cementitious matrix synergistically interconnect, leading to a different mechanical performance which needs to be studied. In this paper, the effect of the addition of microfibers to 3D Textile Reinforced Cements (3D TRCs) is investigated, evaluating the influence of the fibers themselves, as well as their content and length. Two types of polypropylene (PP) microfibers with a length of 3 mm and 6 mm are selected. Using four-point bending tests linked with Digital Image Correlation (DIC) monitoring, the strain-hardening behavior, bending behavior and crack formation of 3D TRC specimens with and without added microfibers are investigated. Generally, using 3D textiles, a superior flexural response is already obtained compared to 2D textiles due to the anchorage mechanism of the transversal connections. However, a higher ultimate load and post-cracking stiffness are achieved upon using synthetic microfibers, showing the positive effect of the reinforcement combination. A higher fiber content and longer fiber length amplify this effect. Furthermore, the addition of microfibers generally results in the formation of more and narrower cracks.