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The phytochemical investigation of the methanol extract of the seeds of Magydaris pastinacea afforded two undescribed benzofuran glycosides, furomagydarins A-B (1, 2), together with three known coumarins. The structures of the new isolates were elucidated after extensive 1D and 2D NMR experiments as well as HR MS. Compound 1 was able to inhibit the COX-2 expression in RAW264.7 macrophages exposed to lipopolysaccharide, a pro-inflammatory stimulus. RT-qPCR and luciferase reporter assays suggested that compound 1 reduces COX-2 expression at the transcriptional level. Further studies highlighted the capability of compound 1 to suppress the LPS-induced p38MAPK, JNK, and C/EBPβ phosphorylation, leading to COX-2 down-regulation in RAW264.7 macrophages.

Among reinforcement methods for 3D concrete printing (3DCP) structures, steel cable reinforcement and reinforced concrete confined by 3DCP formwork (RC-3DPF) methods offer high design freedom and automation. However, the former lacks reinforcement in directions perpendicular to the printing direction, and the latter cannot satisfy constructional requirements. This paper proposed a hybrid approach: the steel rebar reinforced concrete column confined by the steel cable reinforced 3DCP permanent formwork (RC-SC-3DPF). Axial compression tests and theoretical analysis were conducted to study axial performances. Test results showed steel cables and fibres added to 3DCP formwork benefit RC-SC-3DPF structural performances. With a steel cable confinement ratio above 0.534%, RC-SC-3DPF outperforms the traditional case. Steel fibre, compared to PVA fibre, demonstrates greater potential for RC-SC-3DPF due to improved axial load resistance and reduced ductility loss. A theoretical model, based on experimental results, existing standards, and M&T model, was developed to effectively evaluate RC-SC-3DPF structural behaviour.

This study explores the innovative use of 3D robotic spray for applying self-sensing cementitious coating, emphasising its potential for multifunctional smart concrete applications. The effects of spray parameters on the performance of self-sensing cementitious composites were investigated by systematically examining the impact of nozzle travel speed, air injection pressure, nozzle standoff distance, and spray direction on the self-sensing coating. In-depth analyses were conducted on mechanical strength, coating adhesion properties, and sensing performance. Micro-CT was performed to investigate the coating's inherent porosity. This study evaluated the sensing performance of the coatings by analysing their piezoresistive behaviour under cyclic compression and bending. Furthermore, it demonstrated the coating's capacity for real-time structural health monitoring by evaluating its performance under compressive and bending stresses until failure. This research underscores the significant impact of spray parameters on optimising the sensing capabilities of the self-sensing spray coating, highlighting its potential for advanced real-time structural health monitoring.

Cementitious materials incorporating recycled crumb rubber have become a common sustainable resolution in diverse building environments to achieve various functions in terms of lightweight, ductility, as well as energy absorption. This study explored the 3D printed rubberised cementitious composites (3DPRC) in two aspects: examining the effects of crumb rubber pretreatment conditions on compressive properties; conducting experimental and numerical analysis on the acoustic dissipation characteristics of 3DPRC. Fine crumb rubber granules (3-5 mm) replaced 10%, 20%, and 30% of river sand in the composites. Uniaxial compression tests indicated that the compressive strength of 3DPRC decreased with the increase of crumb rubber content and introduced anisotropic behaviour. Impedance tube tests were conducted to evaluate the sound absorption and insulation capabilities of 3DPRC. An optimal Noise Reduction Coefficient (NRC) of 0.35 was achieved with 30% crumb rubber. The sound insulation properties depend strongly on the mass density and porosity of the 3DPRC. Additionally, it is proved that the volume of built-in air gap has positive effects on both sound absorption and insulation properties. The results from Finite Element Method (FEM) numerical simulations correlated well with experimental data, proving the efficiency of the simulation and validating the experimental results.

ABSTRACTAs global CO2 concentrations rise, there is a pressing need for sustainable alternatives in the construction sector as many countries are striving to attain net carbon neutrality. Integrating carbon capture and sequestration (CCS) technologies directly into 3D concrete printing offer a promising solution to reduce the carbon footprint in the construction sector. This paper investigates a novel printing technique involving the purging of pressurised CO2 gas was demonstrated and the various process parameters were evaluated for its effectiveness in promoting carbon sequestration. Results show that the carbon-sequestrated sample has a 15% increase in carbon uptake as compared to the control sample. The method can be complementary to existing sequestration technologies, facilitating large-scale carbon sequestration without chamber size limitations. Nevertheless, further research and development are necessary to optimise the various printing parameters and achieve a more balanced and efficient integration of carbon capture and sequestration technologies with 3DCP.

The varying physical property in a functionally graded material can be tailored to its specific requirements while using material resources effectively. 3D concrete printing can produce robust and lightweight functionally graded material for the construction industry. In this study, an approach was developed to create an objective tailored functionally graded concrete material by examining the filament material property correlations with the printing parameters. It was found that the physical property of the printed material is closely correlated to the flow rate and travel speed of the printer. Results obtained from the experiment show that the optimised structure achieved an approximately 50% improvement in the strength-to-weight ratio. This preliminary examination of the 2D optimised concrete structure opens the realm of possibility for future work in 3D optimised functionally graded concrete.

3D Concrete Printing (3DCP) has been gaining popularity in the past few years. Due to the nature of line-by-line printing and the slump of the material deposition in each extruded line, 3D printed structures exhibit obvious lines or marks at the layer interface, which affects surface finish quality and potentially affect bonding strength between layers. This makes it necessary to control the extrudate formation in 3DCP. However, it is difficult to directly analyse the extrudate formation process because the extrudate shape depends on many parameters. In this paper, a machine learning technique is applied to correlate the formation of the extrudate to the printing parameters using an Artificial Neural Network model. The training data for the model development was obtained from extrudates printed in 3DCP experiments. The performance of the trained model was experimentally validated and the predicted extrudate geometry resulting from the developed model showed good agreement to the actual extrudate geometry. Subsequently, the developed model was used to find proper nozzle shapes to produce designated extrudate geometries. Significant improvement on the printing quality was demonstrated using nozzle shapes generated from the model on 3D printed objects consisting a vertical wall, an inclined wall and a curved part.

To demonstrate printability and fire performance of 3D printable fibre reinforced cementitious materials at elevated temperatures, large-scaling printing and fire performance testing are required for engineering applications. In this work, a mixture design of 3D printable fibre reinforced cementitious composite (3DPFRCC) for large-scale printing was developed. A structure with dimensions of 78 × 60 × 90 cm (L × W × H) was printed by a gantry printer in 150 min, which demonstrates that the developed 3DPFRCC mixture possesses good buildability. The rheological property, setting-time, and mechanical properties under normal and elevated temperatures of the developed 3DPFRCC were then characterised. Final results indicate that the developed 3DPFRCC is suitable for engineering applications due to its good printability and mechanical properties under normal and elevated temperatures.

An advancing technology that combines the concrete extrusion with a motion control to create structures with complex geometrical shapes without the need for formwork is known as 3D concrete printing. Since this technique prints layer by layer, the time taken to reach the same position in the subsequent layer is important as it will create an anisotropic property that has a weaker tensile strength at the bond interface of the two printed filaments. Through rheological measurement, which reveals the material deformation and flow behaviour, it is possible to examine the material structural build-up due to time-gap effect by measuring at different time delay. This paper focuses on investigating the time-gap effect on the printed filament with rheological and observation at macroscopic-scale to understand the material behaviour of the initial and subsequent printed layer during its fresh phase. Rheological experiment findings reveal that the tensile strength of the printed specimen is correlated to the material modulus at the initial layer.

Three-dimensional (3D) printing (also known as additive manufacturing) is an advanced manufacturing process that can produce complex shape geometries automatically from a 3D computer-aided design model without any tooling, dies and fixtures. This automated manufacturing process has been applied to many diverse fields of industries today due to significant advantages of creating functional prototypes in reasonable build time with less human intervention and minimum material wastage. However, a more recent application of this technology towards the built environment seems to improve our traditional building strategies while reducing the need for human resources, high capital investments and additional formworks. Research interest in employing 3D printing for building and construction has increased exponentially in the past few years. This paper reviews the latest research trends in the discipline by analysing publications from 1997 to 2016. Some recent developments for 3D concrete printing at the Singapore Centre for 3D Printing are also discussed here. Finally, this paper gives a brief description of future work that can be done to improve both the capability and printing quality of the current systems.