Nicolas Ducoulombier

XtreeE · R&D

The rapid development of 3D concrete printing now offers mechanical efficiency and freedom to push the limits of construction design. The digital manufacturing process holds potential for reducing carbon footprints through design optimization. Printable concrete, which is a mix of cement (based on ordinary Portland cement), aggregates, and admixtur...

High packing density is one of the key factors for obtaining ultra-high-performance cementitious materials in the hardened state. Packing density also plays a role in the fresh state, influencing various properties of dense suspensions, including rheological properties and stability, which are highly important in 3d printing applications. The maxim...

Significant developments in 3D concrete have been made over the past few decades. Yet, unreinforced printed components generally do not comply with existing construction standards or regulations and are therefore not used as load-bearing components. There is still a gap between research and use, and despite several proposals, standard commercial so...

The control of mortar rheology is of paramount importance in 3D printing concrete by extrusion. This is particularly sensitive for two-component (2K) processes that use an accelerator to switch the printed mortar very quickly from a liquid behavior to a sufficiently solid behavior to be able to be printed (i.e. structuration). After some main key p...

The control of mortar rheology is of paramount importance in the design of systems and structures in 3D printing concrete by extrusion. This is particularly sensitive for two-component (2K) processes that use an accelerator to switch the printed mortar very quickly from a liquid behavior to a sufficiently solid behavior to be able to be printed. It...

This article investigates the application of a multi-robotic platform to the fabrication of complex “free-form” timber structures. A concept of “smart factory”, with a 13-DOF robotic cell combining robotic mobility with fixed workstations, is proposed. A computational workflow was implemented to allow for fast iterations during the early design sta...

We focus in this paper on the embodied and operational contribution to climate change of a concrete-printing robotic cell. We first propose, in the case of extrusion-based additive manufacturing, a simple functional unit that relates a volume-based material impact and a time-based process impact through the printing head velocity and the filament c...

The issue of reinforcement for 3D concrete printing has received considerable attention, as constructions have to comply with reliability principles and building standards. Here a specific process called Flow-Based Pultrusion for additive manufacturing (FBP), inspired by pultruded composite manufacturing and built on existing extrusion-based 3D pri...

In the absence of a formwork, printable materials are expected to quickly increase their consistency in order to resist the self-weight of the structure being printed. Resolving this rheological requirement with the printing process is the key to successful printing. It is therefore necessary, from a material design, from a process design and from...

Important developments in additive manufacturing with concrete have been achieved in the past decades. Yet, printed components usually do not comply with building standards or basic reliability principles, and are not commonly used as load-bearing components. A gap between research and practice exists and despite several attempts, off-the-shelf com...

This paper introduces a novel rheological technique allowing for the assessment of printable materials yield stress at nozzle exit in the case of extrusion-based 3D printing. This technique is derived from the analysis of the specific gravity-induced non-Newtonian flow that takes place at nozzle exit, which is at the origin of the formation of mate...

The vast majority of applications of extrusion-based concrete additive manufacturing deal with unreinforced mortar. The lack of reinforcement is a serious limitation for the industrial development of 3d printed concrete, because of the brittleness and lack of tensile strength of unreinforced mortar. In this paper, a new reinforcement method inspire...

This work focuses on the reinforcement strategies for large scale additive manufacturing of cementitious materials. This new process allows an important geometrical complexity for constructive elements, generally consuming a lot of material and human resources. In addition, it makes it theoretically possible to industrialize the manufacture of sing...

3d printing of cementitious material by pressing layers during the extrusion is a strategy that requires a rather low initial yield stress so the material can deform without cracking. It allows to perfectly control the height of the layer and gives freedom in the orientation of the printing head and of the layer allowing for a wider range of printa...

Successful and efficient fabrication using robotic extrusion of cementitious materials mainly relies on the mastering of the printable material fresh state behavior. This paper tackles this aspect by introducing a novel rheological apparatus dedicated to the yield stress measurement at nozzle exit in extrusion-based manufacturing. It is based on th...

This paper proposes a specific extrusion method for 3D printing of mortar called free deposition by the authors. It consists in letting a fine mortar flow through a moving nozzle above a support, here EPS foam. The aim is to obtain a regular lace, thus to avoid instability phenomena like coiling, and ensure a regular diameter, without stretching th...

For the last decades, new reparation or fabrication processes have been studied to replace traditional rebar by roving of different mineral or organic fibres to avoid corrosion issues. Such materials refer to the family of cementitious composite. Their tensile strength would directly depend on the proportion of reinforcement and strongly on the int...

For the tens past years, important development has been achieved on the adaptation of additive manufacturing to the construction industry using concrete. They mostly concerns control rheology at fresh state, setting time, and technology advances. Nevertheless, the reinforcement of 3D printed part remains an open question. Different reinforcement pr...

The aim of this paper is to discuss the dialectic form-finding of a complex timber structure based on an innovative structural system: shell-nexorade hybrids. Nexorades, also known as reciprocal frames are elegant structures that suffer from a relatively poor structural behavior due to in-plane shear and bending of the members. Introducing plates a...

This paper presents the design and fabrication of an innovative structure, spanning 6.5m with a structural thickness of 12cm. The structural system derives from nexorades, also called reciprocal frames by some authors, obtained by a novel form-finding method based upon translation of the edges. It also allows for the covering with planar facets if...

In this paper phenomenological observations of the creep rupture under maintained combined traction and torsion loading are first presented. They show the importance of the matrix's behavior in the long-term durability of the material. Understanding and foreseeing creep rupture of unidirectional fiber reinforced polymers (UD FRP) involves comprehen...