Tensile and flexural properties of 3D-printed jackets-reinforced mortar

Recently, 3D printing technology has been rapidly developing in the construction sector around the world. However, the insufficient tensile and flexural strengths of the printed material is a crucial problem due to the difficulty of applying steel reinforcement. As a printable material, fibres can be added to the mixture to improve the post-cracking behaviour and toughness of reinforced mortar. Therefore, the present study proposes a 3D-printed fibre-reinforced mortar frame with basalt and carbon fibres to develop a fibre-jacket-reinforced specimen. Specimens with different numbers of reinforcing layers (two, four and six layers) and four different printing paths were fabricated to investigate the strengthening effect on both flexural and tensile capacities. Results from both tests show that a properly designed printing path can significantly improve the tensile and flexural strengths of 3D-printed mortar due to the fibre alignment effect. The strength of fibre-jacket-reinforced specimens is enhanced to a different extent compared with the strength of cast specimens without fibre (with maximum flexural strengths of up to 167% and splitting tensile strengths of up to 128% compared with the respective strengths of the control groups). Meanwhile, both strengths of the fibre-jacket-reinforced specimens with six reinforcement layers almost reach the same strengths of a fully printed fibre-reinforced specimen, but the amount of fibre is reduced by half. In addition, an electromechanical impedance (EMI) technique is applied to monitor the damage during the loading process and an analytical model is developed to predict the enhanced bending capacities of the proposed fibre-jacket-reinforced specimens. (c) 2021 Elsevier Ltd. All rights reserved.