M.J. Tan

Nanyang Technological University | ntu · School of Mechanical and Aerospace Engineering (MAE)

Profound reliance of the building and construction sector on cement exacerbates its immense carbon footprint, accounting for a substantial portion of worldwide emissions. In this paper, we investigate the possibilities of in-situ carbon capture and sequestration to eliminate spatial constraints from a chamber confined curing solution via CO2 and st...

The advent of 3D construction printing has ushered in a revolutionary era, demanding deeper insights into the understanding of cementitious fluid materials. Despite notable progress in additive manufacturing technologies, traditional rheological models (i.e., Bingham Plastic and Herschel-Bulkley) due to asymptotic behaviors of its plastic viscosity...

Extraterrestrial exploration, represented by Lunar base construction, has been promoted worldwide as a multi-disciplinary, cutting-edge and strategic issue. Herein we proposed a novel extraterrestrial construction material composed of Lunar/Martian regolith simulants and only 4 wt% of silicate adhesive. This silicate-regolith composite can be direc...

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...

The advantage of 3DCP technologies is the ability to fabricate free-form structures. However, printing openings in concrete structures are limited by the presence of overhanging sections. While various 3D printing and additive manufacturing technologies have established methods for handling overhangs with temporary supports, many existing technique...

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 spe...

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 re...

There has been a lot of interest in the sustainability aspects of 3D Printing, also known as Additive Manufacturing, due to its potential for resource conservation, localized production, and optimized and adaptive designs. However, quantifying these sustainability advantages has proven to be a challenging task. Several tools have been developed to...

As 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 constr...

Fiber orientation is process-related and has significant impacts on material performance. However, existing studies only consider the impact of individual factors on the fiber orientation, either boundary impacts or flow field impacts. This work aims to study fiber orientation by considering the combined impact of these two factors. Analytical mode...

Utilization of an Electromechanical impedance (EMI) technique with Piezoelectric (PZT) sensors has showed potential for Structural Health Monitoring (SHM). The changes in mechanical structure via flexural bending and cracking can be detected by monitoring the deviations in electrical impedance signals recorded with embedded PZT sensors. This paper...

Selective laser melting (SLM) is a promising additive manufacturing method that falls under the category of powder bed fusion (PBF) technology. It has many advantages such as material versatility, efficiency, and the ability to print complex parts without additional machining. However, its surface quality and fatigue properties have been found to b...

Recently, 3D printing technology has become more popular in the field of construction. For the extrusion-based 3D concrete printing (3DCP) process, the cementitious material needs to be strong and flowable enough to ensure buildability and pumpability. Nanostructured silica, a kind of additive, has been used to modify the 3DCP concrete to meet thes...

Concrete 3D printing is a sustainable solution for manufacturing efficient designs and creating less waste, and selecting the optimal materials to use can amplify the advantages of this technology. In this study, we explore printing lightweight concrete by replacing normal weight aggregate with lightweight aggregates such as cenospheres, perlite, a...

In Singapore, there is an increasing need for independence from manpower within the Building and Construction (B&C) Industry. Prefabricated Prefinished Volumetric Construction (PPVC) production is mainly driven by benefits in environmental pollution reduction, improved productivity, quality control, and customizability. However, overall cost saving...

The greenhouse gas (GHG) emissions into the atmosphere contributes to global climate change, drawing concerns from scientists and governments worldwide. With the introduction of the fourth industrial revolution, the digitalization in the construction method has also been enabled with the advancement of the 3D printing technology. This paper discuss...

In the growing additive manufacturing (AM) industry, there are growing demands for better as-built surface quality of parts fabricated by selective laser melting (SLM) process, especially for the aerospace, medical and tooling industrial sectors. The surface of SLM parts is relatively bad due to the inherent layer-by-layer processing method. Curren...

Energy consumed in building and construction accounts for 40% of the total end-use energy. To achieve the energy reduction in this area, conventional construction approaches need to be reshaped. To overcome existing challenges, this study explores the use of 3D cementitious material printing (3DCMP) and investigates the printability of these cement...

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 function...

3D concrete printing (3DCP) is gaining much attention due to the absence of formwork, allowing more freedom in the architectural design, and reducing construction costs significantly. The lack of formwork configuration in the 3DCP technique requires the printable concrete to possess self-supporting properties. Furthermore, the yield stress evolutio...

Three-dimensional (3D) printing for building and construction has gained much attention from both the industry and academics in the past few years. It promises to revolutionize the construction industry with the potential of freeform architecture, less material waste, reduced construction costs, and increased worker safety. Furthermore, the technol...

The effects of Fe doping and applied hydrostatic pressure on structural, mechanical and electronic properties of Zr8Cu8-xFex (x = 0, 1, 2, 3) are investigated via the first-principles calculations. The equation of state (EOS) is established for B2–CuZr crystalline structure. The values are in good agreement with previous experimental results. The p...

This paper studies the effects of recycled glass cullets as fine aggregates for the material in construction 3D printing. A reference material with natural river sand as fine aggregate was used as the control and recycled glass cullet of similar grading was used to replace the natural river sand at 25, 50,75 and 100% by mass. The effects of incorpo...

This study focused on the development of 3D printed building components incorporating MgO–SiO2 binders. The effects of parameters such as MgO/SiO2 and water/binder ratios and superplasticizer dosage were evaluated to produce 3D printable MgO–SiO2 binders. The assessment of rheological and mechanical properties, which led to an optimum mix that sati...

In this paper, a novel method for printing path design in the three-dimensional (3D) concrete printing process (3DCP) has been developed and applied to a large-scale construction process. Despite the large number of research works in digital concrete printing over the last decade, few studies have explored the method of automatic printing path desi...

The safety of structure printed by extrusion-based 3D concrete printing (3DCP) is significantly influenced by interlayer bonding, which is governed by fresh material properties and processes, including mixing, printing, and post-processing phases. Much literature focused on improving interlayer bond strength via material tailoring/bonding agent add...

A synchronized concrete and bonding agent deposition system is proposed to address the weak interlayer bond strength issue in extrusion-based 3D concrete printing (3DCP). In the proposed system, printable concrete and bonding agent are deposited concurrently via a rotatable nozzle with two outlets. Therefore, the interlayer bond strength is improve...

Friction stir processing is a solid-state welding technology capable of joining metal parts without the melting. The microstructure of the material evolved during the process vary from columnar grain along the thermal gradient in the melt pool to fine equiaxed grains. Evaluation on its mechanical properties in terms of micro-hardness was performed....

Sustainability is interpreted as the effective use of resources as well as the preservation of the environment. A sustainable building is giving back to the environment more than it takes and ensuring that the resources is being used in an effective way that would benefit the community. A combination of smart design, efficient technology and design...

When conducting corner printing with rotational rectangular nozzle, a greater amount of material is deposited inside the filament and hence tearing and skewing will occur on the surface of the printed filament. With the aim of maintaining the surface finish and mechanical properties of the printed filament, a 3D numerical model is developed to stud...

3D printing enables on-demand solutions for a wide spectrum of needs ranging from personal protection equipment to medical devices and isolation wards. This versatile technology is suited to address supply–demand imbalances caused by socio-economic trends and disruptions in supply chains.

The material flow mechanism affects the printing quality considerably in 3D cementitious material printing (3DCMP) area. A numerical model was developed to investigate the material flow mechanism during the extrusion and deposition process. To quantify the effects of flow mechanism on the filament printing quality, deformation of the printed filame...

The purpose of this study is to perform a comparative study of economic cost, environmental impacts, and productivity associated with manufacturing a prefabricated bathroom unit (PBU, L: 1620 mm; W: 1500 mm; H: 2800 mm) via extrusion-based 3D concrete printing (3DCP) and a precast approach, respectively. The scope of this study includes material co...

3D concrete printing technology greatly facilitates automation in construction which enhances efficiency, productivity and sustainability. This study develops a slag-based mixture as a cementless material for sustainable spray-based 3D printing. Effects of MgO and fly ash cenosphere (FAC) addition on setting, hydration and rheological properties of...

This study investigated the properties of alkali activated slag (AAS) binders formulated for extrusion-based 3D printing. The fresh properties of AAS mixes were tailored through the use of nanoclay (NC) and nucleation seeds. The printability criteria employed were the ease of extrusion (extrudability) and the stability of the layered structure (bui...

Purpose In recent years, additive manufacturing techniques have attracted much research attention because of their ability to fabricate customised parts with complex geometry. The range of composites suitable for laser-based powder bed fusion technique is limited, and has not been investigated yet. This paper aims to study the fabrication of AlSi 1...

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 la...

The employment of automation in construction has not yet reached its full potential. 3D concrete printing is one of the promising construction techniques which has drawn a lot of attention due to its unique benefit in terms of higher productivity, faster construction processes, geometrical freedom, and cost-efficiency. With the number of 3D printin...

This study investigates the influence of wire drawing practices, namely Full Die Drawing (FDD) and Half Die Drawing (HDD) on the fatigue performance of MP35NLT wires. The as-drawn wires were subjected to rotary beam fatigue tests with varying stress amplitudes, and the cyclic performance of the wires in the LCF and HCF regimes was determined. A rel...

he employment of automation in construction has not yet reached its full potential. 3D concrete printing is one of the promising construction techniques which has drawn a lot of attention due to its unique benefit in terms of higher productivity, faster construction processes, geometrical freedom, and cost-efficiency. With the number of 3D printing...

Wide gap transient liquid phase (TLP) bonding could be used for repairing large cracks or worn areas on aerospace components. Unfortunately, the residual borides in the joints after bonding might deteriorate their mechanical properties. Increasing bonding time or temperature could effectively reduce the fraction of borides and strengthen the joints...

This study focused on the suitability of geopolymer mixes for extrusion-based additive manufacturing applications. Geopolymer mixes including alkaline potassium silicate activator with different molar ratios were prepared and evaluated for their rheological responses (e.g. yield stress, viscosity and thixotropy) that influenced their extrudability...

The potential of digital manufacturing of concrete or 3D concrete printing (3DCP) is represented by various innovative projects and research around the world. Although several showcases of concrete printed structures are available worldwide, many challenges remain at the technical and processing level. A recurring issue associated with 3DCP is the...

The advent of digital concrete fabrication calls for advancing our understanding of the interaction of 3D printing with material rheology and print parameters, in addition to developing new measurement and control techniques. Thixotropy is the main challenge associated with printable material, which offers high yield strength and low viscosity. The...

In recent times, sintered brazing preform is used in the TLP bonding applications as it only undergoes partial melting during bonding, thus preserving its designed geometries. In this paper, the effects of bonding time on the transient liquid phase bonding joint of Inconel 718 using a new nickel-based sintered brazing preform was investigated. The...

35%Co-20%Cr-35%Ni-10%Mo alloy (MP35N) with a low titanium (LT) content is commonly used as the material for the manufacture of leads in medical applications such as Cardiac Rhythmic Management (CRM), neurostimulation and Deep Brain Stimulation (DBS). The material is drawn to thin wires, and this involves subjecting the material to extensive plastic...

3D printing, or additive manufacturing, is a technology which adopts layer-by-layer additive deposition process to build three-dimensional objects. Over the past decade, 3D printing has been attracting more and more attention in the building and construction industry. Compared with conventional concrete casting techniques, 3D printing contributes t...

Rheological studies are important for successful 3D concrete printing. The main challenge for successful 3D concrete printing is the complex characteristic the materials should possess. It should be flowable enough to be pumped and extruded through the hose, as well as gaining sufficient strength and stiffness for buildability after the layer by la...

3D concrete printing can be used to build many complex structures. However, due to its material properties in the fresh state, it is difficult to construct overhanging structures without supports. In order to unleash the true capability of 3D concrete printing, a support structure is required to support any overhanging fresh material, which is usua...

Transient liquid phase (TLP) bonding of Inconel 718 with BNi-2 filler metal has traditionally been carried out using thin filler metal (narrow gap) to achieve complete eutectic-free isothermal solidification layer joints. However, for the aerospace components with relatively large cracks or worn areas where a large amount of filler metal is needed,...

The disposal of post-consumer glass has been a major issue due to its inert properties that may cause environmental effects. While recycling of these glass is only feasible if the waste glass recovered is sorted into its different colour to prevent chemical incompatibility in the manufacturing process. 3D printing in building and construction have...

Plastic instability of Co-35Ni-20Cr-10Mo alloy was studied by inflicting the material to the different drawing process, namely Full Die Drawing (FDD) and Half Die Drawing (HDD). The wires were subjected to different plastic deformations, by varying the amount of cold work (CW) reduction, and the strain hardening exponent (γ) and strain rate sensiti...

Interest in innovative construction processes such as 3D concrete printing (i.e. digital construction), is growing rapidly both in academia and industry. Processing conventional geopolymer mixes, in which alkaline solutions are used for activation, could be troublesome in concrete printing due to the high viscosity of the alkaline solution. One-par...

Digital construction is gradually opening unlimited possibilities for building and concrete industry. The key secret for a robust print process lies in our understanding of the processing technology and material fresh properties, in addition to developing novel measurement and control techniques. This paper aims to gain a better understanding of ea...

This study investigates the effect of strain rate (SR) on the strain rate sensitivity (SRS), strain rate work hardening (SRWH) in Co–35Ni–20Cr–10Mo alloy (MP35N) wires, subjected to drawing practices namely full die drawing (FDD) and half die drawing (HDD). The experimental results illustrate that the strength, and SRWH, of the drawn wires, increas...

3D printing is getting significant attention in the construction industry. This technology, which has been talked for years, is now delivering tangible results, however it is not yet ready for mass production in mainstream construction. Thixotropy material, 3D printer together with 3-dimensional computer model are the key elements required for robu...

3D printing has been getting increasing attention from both industry and academy in recent years. Unlike traditional construction processes, 3D cementitious material printing requires more accurate control on the pumping flow rate, which is known to be affected by the material rheology. In this paper, the effect of fresh rheology on the flow rate o...

To demonstrate printability and fire performance of 3D printable fiber 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 fiber reinforced cementitious composite (3DPFRCC) for large-scale printing wa...

Friction stir welding of selective laser melting printed AlSi10Mg and AlSi10Mg -2% wt. nAl2O3 parts were conducted. This study investigated the weldability and mechanical properties of the welds by evaluating their chemical composition, porosity, weld microstructure evolution, micro-hardness and tensile strength. The selective laser melting fabrica...

Generally, transient liquid phase (TLP) bonding is conducted with an overdose of filler metal in a vacuum furnace that necessitates excessive post machining. Recently, a new form of filler metal, the sintered brazing preforms (SBP) has been introduced to achieve a neat TLP bonding joint, which undergoes partial melting and retains its original shap...

Digital construction has recently become the subject of very rapidly growing research activities all over the world. In this regard, our current research demonstrates the possibility of using high volume fly ash mortar, modified with micro silica, for 3D concrete printing application. To assess the effect of the micro silica on rheological performa...

In this study, a high-volume slag mortar was formulated according to rheology requirements of 3D concrete printing. In addition to the slag, 10-20% Portland cement (PC) and 5-10% hydrated lime were considered to enhance the early age mechanical properties and their respective flow properties were characterised using thixotropy based rheology protoc...

3D Printing or additive manufacturing has been gaining popularity in the concrete research community and the field. Compared with conventional vibrating concrete or self-consolidating concrete, 3D printing technique do not require formwork, which is labor intensive and costly in construction sites. With the advantages in depositing the materials fr...

This study investigates the influence of cold wire drawing practices namely full die drawing (FDD) and half die drawing (HDD) on the deformation homogeneity in Co-35Ni-20Cr-10Mo alloy (MP35N) wires which are used for manufacturing implantable medical products. The inhomogeneous factor was used to assess the level of inhomogeneity in the wires, and...

The added capabilities of Additive Manufacturing (AM) while processing metallic components have revolutionized the design and manufacturing flexibility of multitudes of aerospace components. However, AM being a stochastic process results in a degraded control of the surface topography of the printed structure and thus requires adequate finishing pr...

The effect of nano-attapulgite clay (NC) addition on the fresh, hardened and microstructural properties of high volume fly ash (HVFA) mixes designed for 3D printing was investigated in this study. Experimental results showed that the addition of 0.1–0.5% (i.e. by mass of binder) NC increased the static yield stress of HVFA mortars without significa...

This study presents the development of fly ash-based geopolymer mixtures for 3D concrete printing. The influence of up to 10% ground granulated blast-furnace slag (GGBS) and silica fume (SF) inclusion within geopolymer blends cured under ambient conditions was investigated in terms of fresh and hardened properties. Evolution of yield stress and thi...