The growing interest in sustainable and high-performance asphalt materials has increased the need for alternative modifier including recycled polymeric wastes. Although SBS is widely used in asphalt modification, its limitations relate to cost, compatibility, and storage stability have encouraged the development of hybrid modification strategies. In this study, recycled EPDM and polyurethane were combined to evaluate their collective influence on the rheological and performance-related properties of asphalt binder. First, normal and devulcanized EPDM-modified binders were compared to determine the more effective EPDM type. Then, pure bitumen, 6
This study presents an integrated design-to-construction framework for a large-scale spatial hyperbolic paraboloid concrete bridge constructed using 3D printing. The central challenge is to reconcile freeform geometry with structural rationality and manufacturability. To address this challenge, a process-aware digital workflow is developed in which printability constraints, including interlayer offset and overhang limits, were incorporated in the early stages of form generation. The bridge was organized as a discretized-continuous system composed of seven spatial units characterized by non-uniform hollow U-shaped shell sections and a steel–concrete hybrid structural system. Through sequential segmentation, non-planar slicing, adaptive toolpath planning, robotic printing, cavity grouting, and staged on-site assembly, this design was ultimately realized as a full-scale bridge. The completed structure consisted of 73 prefabricated components, including 31 shell modules and 42 deck panels. The total concrete volume of the bridge was 129 m3, of which 56 m3 was produced by 3D printing. Using a single-robot configuration, the printing phase was completed within 15 days, with an average productivity of 3.7 m3/d. Compared with the conventional formwork-based method, the proposed workflow reduced the fabrication-to-delivery duration by approximately 58
Buildability failure in extrusion‑based concrete 3D printing (C3DP) arises from insufficient early‑age structural build‑up in lower layers to sustain subsequent layers. While rheological tests provide insight into material behavior, they do not capture the progressive deformation that develops during printing. This study introduces a practical, non‑intrusive monitoring and supervisory decision support framework that uses layer‑thickness deformation trends to predict and mitigate plastic buildability collapse. While earlier studies showed that geometric deformation provides insight into structural build-up, this study extends deformation analysis to collapse prediction. A geometric metric, Maximum Layer Thickness Deformation (MLTD), and its temporal evolution are extracted from 2D images to quantify the deformation during printing. Results show that collapse‑prone elements exhibit rapidly increasing deformation rates, whereas stable elements maintain consistently low deformation rates. A magnitude and persistence-based collapse-prediction algorithm with a limiting boundary on the slope of the last two MLTDs enables collapse prediction several layers in advance. The deformation‑rate indicator shows qualitative agreement with squeeze‑flow stress–strain trends, indirectly reflecting early‑age structural build-up. A supervisory decision-support strategy based on deformation-rate is proposed to guide iterative corrective actions for collapse mitigation, replacing heuristic operator decisions with data‑driven decisions. A dimensionless speed ratio is introduced as a pre-print collapse indicator and a coordinated control parameter. The robustness of the proposed framework is demonstrated using 42 experimental prints involving variations in printing speed, retention time, geometry, lighting conditions, and print scale. Overall, the proposed framework establishes a practical, real‑time buildability failure prediction and supervisory decision-support that enhances reliability in C3DP.
The high-value utilization of waste polyethylene (PE) provides an effective strategy for mitigating plastic pollution while improving asphalt pavement performance. To address the poor interfacial compatibility between basalt fiber (BF) and asphalt, the aggregation tendency of carbon nanotubes (CNTs), and the limited catalytic efficiency and capability of monometallic and bimetallic catalysts to regulate the structures of CNTs, this study used a Ni–Mg–Al ternary composite catalyst to grow CNTs in situ on the BF surface using waste PE as the carbon source. The resulting CNTs–BF hybrids were incorporated into asphalt to evaluate their reinforcing effects. The influence of pyrolysis temperature on the morphology and microstructure of CNTs was systematically investigated. The results showed that well-defined bamboo-like CNTs with comparatively high graphitic ordering were formed at 800 °C after a holding time of 3 h, and TEM observations suggested the possible coexistence of tip-growth and base-growth modes. At a CNTs–BF content of 3 wt
This study evaluates a one-part blended fly ash (FA)—ground granulated blast furnace slag (GGBS) geopolymer plaster coating activated by solid sodium metasilicate, with emphasis on the influence of water-to-binder (W/B) ratio on fire resistance and thermomechanical performance. This study investigates the influence of water-to-binder ratio on the microstructural evolution, thermo-mechanical compatibility, and fire performance of a one-part geopolymer plaster coating using an integrated combination of synchrotron X-ray tomography, micro-XRF, and neutron diffraction. W/B ratios ranging from 0.26 to 0.34 were evaluated to optimise thermo-mechanical behaviour. The geopolymer with a W/B ratio of 0.34 exhibited the best overall performance, achieving a compressive strength of 40.45 MPa, adhesion strength of 2.832 MPa, and residual strength of 19.35 MPa after exposure to 800 °C, while maintaining low water absorption (13.98
