Three-dimensional printed concrete (3DPC) is increasingly recognized in the construction industry for its high design flexibility and the elimination of conventional formwork. However, weak interlayer adhesion remains a significant challenge. The potential of recycled polyethylene terephthalate (PET) fibers for reinforcing 3DPC is being explored, driven by their environmental sustainability and economic advantages. However, there is an inadequate interfacial adhesion between these recycled fibers and the 3DPC matrix. This study investigated the use of dopamine modification to address this issue and enhance the interlayer adhesion of fiber-reinforced 3DPC. Recycled PET fibers were surface-modified using dopamine treatment, forming a polydopamine (PDA) film that improved surface roughness and hydrophilicity. Both unmodified and modified fibers were incorporated into 3DPC at various volume fractions (0.1%, 0.3%, 0.5%). The effects on interlayer adhesion strength, compressive strength, and flexural strength were systematically evaluated and compared. The results showed that the inclusion of 0.3 vol% dopamine-modified fibers resulted in a 22.5% increase in interlayer adhesion strength compared to the control group, and a 14.8% improvement over unmodified fibers at the same content. Additionally, the compressive strength and flexural strength of 3DPC with 0.3 vol% MPET fibers increased by 22.5% and 27.6%, respectively, compared to the control group. Microstructural analysis using SEM and XRD revealed that the dopamine modification significantly improved the interfacial adhesion between fibers and the concrete matrix, explaining the superior performance of modified fibers. This study demonstrates that recycled PET fibers modified with dopamine can effectively enhance the interlayer adhesion of 3DPC. The findings affirm that surface modification techniques can significantly elevate the utility of recycled PET fibers in 3DPC, contributing to the sustainable advancement of construction materials.
3D printed concrete has emerged as one of the most hotly researched 3D printing technologies due to its advantages of shaping without molds and intelligent construction. Given its low heat of hydration and low carbon emissions slag-based cement is becoming more widely used for 3D printing concrete. However, in the formwork-free shaping process, freshly printed slag-based concrete is immediately exposed to air and loses moisture much earlier than traditional cast-in-formwork concrete. As a result, there is a greater risk of drying shrinkage and cracking and poor volumetric stability of the printed part. This study investigated applicability of photopolymerization technology in improving the volumetric stability of 3D printed concrete by using UV-curable polyurethane-acrylate (PUA) resin as in-situ sprayed coating on the surface of freshly printed slag-based cement samples. The results show that, in comparison with the uncoated 3D printed cement samples, the volumetric shrinkage of the coated 3D printed cement samples significantly reduced by 44 % after 28 days of environmental curing. For samples of the same age, the compressive strength of the coated test block was increased by 27 % from 20.03 MPa to 25.49 MPa, and the interlayer bond strength was increased by 41 % from 1.46 MPa to 2.06 MPa. The sprayed UV-curable polyurethane-acrylate resin can cure rapidly on the specimen surface within seconds under the irradiation of UV light to form an in-situ protective coating, which is tightly bonded to the surface of the cement, effectively reducing water dissipation and promoting hydration, allowing more even and condense microstructures to form during hydration from the outer surface to the inner part of the printed sample, resulted in a higher strength.
危险品化学品经营许可证（带存储）