Yu Chen

Delft University of Technology | TU · Department of Materials, Mechanics, Management & Design (3Md)

In 3D concrete printing (3DCP), it is necessary to meet contradicting rheological requirements: high fluidity during pumping and extrusion, and high stability and viscosity at rest to build the layered structure. In this paper, the impact of the hydroxypropyl methylcellulose (HPMC)-based viscosity-modifying admixture (VMA) on the 3D printability an...

This study aims to investigate the influences of different grades of calcined clay on 3D printability, compressive strength (7 days), and hydration of limestone and calcined clay-based cementitious materials. Calcined clays that contained various amounts of metakaolin were achieved by blending low-grade calcined clay (LGCC) and high- grade calcined...

For a single batch material, time intervals and nozzle standoff distances between two subsequent layers are two critical printing parameters that influence the mechanical performance of the printed concrete. This paper presents an experimental and numerical study to investigate the impacts of these printing parameters on the interlayer bond strengt...

This paper aims to investigate the influences of high Portland cement substitutions (>60 wt%) by low-grade calcined clay (CC) and limestone (LF) on 3D concrete printability, stiffness evolution and early-age hydration. Results show that, with the same dosage of admixtures (superplasticizer and viscosity modifier), increasing LF and CC content reduc...

For many 3D printed cementitious materials, air voids may play a dominant role in the interlayer bond strength. However, to date, far too little attention has been paid to reveal the air void characteristics in 3D printed cementitious materials. Therefore, to fill this gap, this study attempts to provide an example of systematically characterizing...

This study investigated the evolution process of high-volume slag cement (HVSC) paste from a chemo-mechanical standpoint. HVSC specimens with a 70 w.t. % slag replacement rate were studied at various ages. Evolution of phase assemblage, microstructure development, and micromechanical properties were analyzed using TGA/XRD/MIP/SEM-EDS and nano-/micr...

Herein, different kinds of methods for buildability quantification of 3D concrete printing are reviewed, including experimental approaches, analytical modelling, and numerical simulations. A brief introduction on printing process is first given. This discusses the material properties in different stages. Material printability, which encompasses pum...

Limestone-calcined clay-cement (LC3), as one of the most promising sustainable cements, has been under development over the past decade. However, many uncertainties remain regarding its rheological behaviors, such as the metakaolin content of calcined clay. This study aims to investigate the effect of increasing the content of fine-grained metakaol...

This paper proposes the use of desalination brine as a setting and hydration activator in set-on-demand 3D concrete printing. A series of tests were conducted to investigate the effect of adding different concentrations of desalination brine on stiffness evolution and early-age hydration of Portland cement mortars (PC mixtures) and limestone-calcin...

Early‐age stress (EAS) is an important index for evaluating the early‐age cracking risk of concrete. This paper encompasses a thermo‐chemo‐mechanical (TCM) model and active ensemble learning (AEL) for predicting the EAS evolution. The TCM model provides the data for the AEL model. First, based on Fourier's law, Arrhenius’ equation, and rate‐type cr...

In this paper, both synthetic slag and commercial slag covering the common composition range were employed to estimate the correlation between slag chemistry and reactivity through hydraulicity and dissolution tests. It was found that slag reactivity was favorably affected by increasing Al2O3 and MgO contents, while the adverse effect of decreasing...

A good bond between the layers of 3D printed cementitious materials is a prerequisite for having high structural rigidity for the printed elements. However, the influence of printing process on an interlayer bond is still not well understood. This study investigates the influence of curing methods (i.e., air curing, plastic film covering, wet towel...

This paper aims to provide a systematical review of the available printing strategies, sustainable cementitious materials and characterization methods for extrusion-based 3D concrete printing (3DCP). The printing strategies, consisting of printing setup, process, and material requirements, were summarized initially. In the material aspect, the high...

Remarkable attention from both academia and industry has been attracted to extrusion-based 3D concrete printing (3DCP) during the last decade. Many companies in the Netherlands, e.g., Royal BAM Group, CyBe, Twente Additive Manufacturing, and Bruil, are attempting to implement this technology in practice. 3DCP is the focused digital concrete manufac...

This paper explores the sustainability aspects of binders used in concrete 3D concrete printing. Firstly, a prospective approach to conduct sustainability assessment based on the life cycle of 3D printed structures is presented, which also highlights the importance of considering the functional requirements of the mixes used for 3D printing. The po...

This paper presents an experimental investigation on the short-term creep recovery of cement paste at micro-metre length scale. Micro-cantilever beams were fabricated and tested with 8 different loading series using the nanoindenter. It is found that cement pastes show high recovery ratios (>80%) even subjected to very high stress levels. Relativel...

In this work, the lattice model is applied to study the printing process and quantify the buildability (i.e., the maximum height that can be printed) for 3D concrete printing (3DCP). The model simulates structural failure by incorporating an element birth technique, time‐dependent stiffness and strength, printing velocity, non‐uniform gravitational...

This study proposes an experimental method for studying the short-term creep behaviour of cement paste at micro-scale. The micro-bending tests on miniaturized cantilever beams were used to characterize the viscoelastic properties of cement paste. The effects of w/b ratio, the type of binder and the stress level on the microscopic creep behaviour we...

Recently, our group attempted to develop the ternary blended (Portland cement, calcined clay and limestone) cementitious material for 3D concrete printing (3DCP). Due to the elimination of formwork during the layer-by-layer casting process, the printed material should have favorable elastic properties and green strength at the fresh state. A small...

The goal of this study is to investigate the effects of different grades of calcined clay on the extrudability and early-age strength development under ambient conditions. Four mix designs were proposed. Three of them contained high, medium, and low grades of calcined clay, respectively, and one was the reference without calcined clay. In terms of...

To investigate the effects of viscosity-modifying admixture (VMA) on the extrudability of limestone and calcined clay-based cementitious materials, three mix designs with different dosages of VMA were proposed in this study. The ram extrusion was utilized as an extrusion model for exploring the fresh properties of printable materials. Two methods w...

In conventional concrete, replacing high-volume (more than 45%) of ordinary Portland cement (OPC) by supplementary cementitious materials (SCMs) is not a novel CO2 reduction method, whereas rarely in 3D printable concrete. This study attempts to explore the feasibility of using SCMs in 3D printable concrete. Initially, the existing binder mixes, re...

Concrete is by volume the most widely used building material all over the world. The concrete industry emits large quantities of greenhouse gases. Therefore, developing low CO2 concrete becomes an urgent issue for those countries with significant concrete production and consumption. In recent years, 3D concrete printing (3DCP) which is a new concre...

Concrete is by volume the most widely used building material all over the world. The concrete industry emits large quantities of greenhouse gases. Therefore, developing low CO2 concrete becomes an urgent issue for those countries with significant concrete production and consumption. In recent years, 3D concrete printing (3DCP) which is a new concre...