Gideon van Zijl

Gideon van Zijl
Stellenbosch University | SUN · Department of Civil Engineering

PhD (Civil Engineering, TU Delft)

About

256
Publications
74,473
Reads
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3,125
Citations
Citations since 2016
126 Research Items
2473 Citations
20162017201820192020202120220100200300400500600
20162017201820192020202120220100200300400500600
20162017201820192020202120220100200300400500600
20162017201820192020202120220100200300400500600
Additional affiliations
January 2010 - December 2015
Stellenbosch University
Position
  • HOD
April 2001 - present
Stellenbosch University
Position
  • Professor of Structural Engineering
Description
  • Head: Division for Structural Engineering and Civil Engineering Informatics
October 1999 - March 2009
Delft University of Technology
Position
  • Research Associate
Description
  • 100% 1999-10 to 2001-04 30% 2001-04 to 2009-03
Education
January 2016 - December 2016
Stellenbosch University
Field of study
  • Structural Engineering
October 1995 - September 1999
Delft University of Technology
Field of study
  • Civil Engineering

Publications

Publications (256)
Article
Full-text available
In this paper the effects of the addition of a paraffin phase change material on the strength and printability of 3D printed concrete are studied. Phase change materials are latent heat storing materials, which garner and release large amounts of energy as they change phase. The addition of phase change materials to concrete produces a composite ma...
Conference Paper
Full-text available
The advancement in modern-day construction has paved the way for the development of a new technology named 3D concrete printing. This technology offers the following merits over conventional cast concrete: improved quality with much less construction cost and wastes, production of high load carrying capacity, and high resistance to environmental ha...
Article
This article focuses on the specifics in characterizing the properties of additively manufactured, cement-based materials in their hardening and hardened states. Such characterization is required for the material development, structural design, and quality control of both printable material and 3D-printed elements. The related challenges are associ...
Article
Full-text available
Practicing engineers typically follow linear methods for seismic design and assessment, confining their approach to the requirements of SANS 10160-4 (SANS 2017). This generally leads to a conservative design, leaving little space to apply additional tools for design refinement. Soil-structure interaction has beneficial effects for most building str...
Article
Full-text available
In this paper a more sustainable 3D printable concrete is developed by the replacement of natural aggregate in a concrete mix with recycled brick aggregate (RBA). An existing 3D printable concrete mix is used as reference and adjusted by replacing 64% of its natural aggregate with RBA. The potential for sustainability in the building sector by auto...
Article
Elements fabricated by extrusion-based 3D concrete printing (3DCP) display anisotropic mechanical properties when subject to loading conditions orientated in principle cartesian axis directions. Various studies show that the mechanical characteristics of 3DCP components are lower than their mould-cast counterparts, reportedly due to the existence o...
Article
The hardened-state mechanical characteristics of 3D printable concrete (3DPC) mixtures exhibit a strong dependence on the employed extrusion-based process, material, and design parameters and are predominantly anisotropic by nature. It has been shown that at the heart of the observed mechanical anisotropy lies the microstructural morphology of the...
Chapter
Rebar penetration is the most common vertical reinforcement strategy for unreinforced 3D printed concrete (U3DPC) structures to improve the axial, flexural and shear capacities, and interlayer bond behaviour. Despite the reasonable simplicity of the application either by a manual or automated system, the method may disturb the fresh material during...
Chapter
Additive technologies in construction, such as 3D printing of concrete, have brought about renewed enthusiasm in the construction sector, mainly due to the principal advantages it presents including reduced cost, time, waste, formwork free manufacturing and free-form parametric design possibilities. Although holistically impressive, the aesthetic a...
Article
Full-text available
The durability of reinforced concrete structures is dependent on the ability of the concrete cover to combat the ingress of chlorides and carbon dioxide in marine and urban environments. In recent years, interest in additive manufacturing), specifically referring to extrusion based three-dimensional concrete printing (3DCP), has been growing in the...
Article
This study investigates the susceptibility of precursor foam in 3D printable foamed concrete (3DP-FC), particularly in aspects of rheology. The relatively higher yield stress, film liquid withdrawal from unsaturated cement grains and the pumping process raises a concern of considerable foam degradation. Foam stability under the static and dynamic e...
Article
Extrusion-based 3D concrete printing (3DCP) prompts a new age of reinforced concrete structures by virtue of the exponential advancements in process, control, material, and fresh-state analysis technologies. Notwithstanding these advancements, latency exists in the numerical analysis of complex geometric forms produced by 3DCP technology. In this r...
Article
This paper investigates the application of nanotechnology in three-dimensional (3D) concrete printing (3DCP), in particular for enhancing thixotropic material behavior, improving buildability or the vertical building rate, and the amelioration of typical 3DCP anisotropic mechanical properties. Two 3D-printable cementitious materials are investigate...
Article
This paper investigates the thermal performance of two candidate 3D printed cement-based façade construction materials, i.e. lightweight foam concrete and high-performance concrete, distinguished by density (1400 versus 2100 kg/m³) and thermal conductivity (0.37 versus 1.1 W/mK). Strategies toward the thermal improvement of 3D concrete printed faça...
Article
Extrusion-based 3DCP is experiencing exponential advancement in process, control, material, and fresh-state analysis technologies, strategically poising 3DCP to become an industrial manufacturing process for infrastructure development. To elucidate the mechanical characterisation and numerical simulation of 3DCP elements synergy among experimental...
Article
In the fresh state, conventional lightweight foam concrete (LWFC) has low yield stress which challenges shape retention and buildability in digital construction. Several literatures attempt to address the rheological performance of 3D printable lightweight foam concrete (3DP-LWFC) in essence. This research presents a comprehensive rheological chara...
Article
Full-text available
Both industry and academia are rapidly developing processes, materials, and projects to explore the potential of extrusion-layering additive manufacturing of cementitious materials, generally known as 3D concrete printing (3DCP). Because the lack of supportive formwork makes objects prone to failure during printing, a key aspect remains the so-call...
Preprint
In the fresh state, conventional lightweight foam concrete (LWFC) has low yield stress which challenges shape retention and buildability in digital construction. Several literatures attempt to address the rheological performance of 3D printable lightweight foam concrete (3DP-LWFC) in essence. This research presents a comprehensive rheological chara...
Article
Full-text available
South Africa has a housing shortage estimated in excess of 2 million units. This backlog is being addressed predominantly with the construction of 40 m2 low-income, single-storey, detached, state-subsidised houses built with conventional concrete masonry units, regulated by the Application of the National Building Regulations, SANS 10400. However,...
Thesis
Full-text available
The imaginative concept of digital construction (DC), through the 3D concrete printing (3DCP) technique, is emerging, driven by the ceaseless efforts of academia and the dynamic collaboration with pioneering start-up companies. The endeavours towards automation in construction are accelerated by the great demand for construction time- and cost-savi...
Article
The most commonly cited obstacles to the uptake of alternative masonry units on a meaningful scale, despite significant research investment, are a lack of standards and understanding of their structural behaviour. This paper contributes to the body of knowledge on finite element analysis of alternative masonry structures, towards improved understan...
Article
Concrete structures additively manufactured by extrusion-based 3D concrete printing are reportedly orthotropic in mechanical behavior and exhibit relative weakness in interfacial regions. Microstructure, including porosity content, 3D porosity distribution and pore morphology presents a physical basis for these phenomena. Here, a first and comprehe...
Conference Paper
In the last decade, the study of three-dimensional concrete printing (3DCP) has become extremely popular, with a number of researchers studying the behaviour of 3DCP at ambient conditions. The interest in 3DCP has been aroused by its ability to facilitate the realization of geometrically complex objects at reduced construction time, and potentially...
Article
The structural integrity of contemporary structures is dependent on the interaction between a brittle concrete matrix and ductile reinforcement. Therefore, reinforcement integration is considered a fundamental subsystem of extrusion-based concrete printing. However, if concrete printing is set to ameliorate the shortcomings of conventional concrete...
Article
Full-text available
This article reviews the literature related to the performance of fiber reinforced concrete (FRC) in the context of the durability of concrete infrastructures. The durability of a concrete infrastructure is defined by its ability to sustain reliable levels of serviceability and structural integrity in environmental exposure which may be harsh witho...
Article
Lack-of-fusion (LOF) in digital concrete fabrication is one of the paramount technical issues that must be elucidated before mass industry implementation of this emerging technology. This review paper initially accentuates the ramifications of poor interlayer bonding, which include impaired mechanical and thermo-mechanical performance in the harden...
Article
The shape retention capability of an extruded filament is of cardinal importance for quality 3D printed concrete elements. Not only is it a prerequisite for surface aesthetics, but it also contributes towards buildability. Optimisation of filament layer height allows for construction time and cost saving possibilities. This research develops the th...
Conference Paper
A successful 3D concrete print (3DCP) is controlled by a sound buildability and good pumpability. Since both factors rely on the behavior of concrete in the fresh state, rheological assessment is crucial prior to 3DCP. In a previous study done by Roussel [1], a correlation of numerical simulation of ASTM mini-slump cone flow and rheometer results w...
Conference Paper
3D concrete printing exhibits the potential to proliferate the industrialization of the concrete construction sector, which is notoriously conservative and indolent towards change. This emerging technology is propitious given its advancements in geometric design freedom, reductions in construction time, waste and material usage through formwork-fre...
Conference Paper
This research examines the differential interlayer capacity of 3D concrete printed (3DCP) specimens via mechanical characterization procedures, comprising of direct tension test (DTT), Iosipescu shear test (IST), and orthogonal compression tests. The experimental findings are subsequently correlated to cohesive parameters that represent the adhesiv...
Conference Paper
This research investigates 3D printed concrete behaviour at elevated temperatures. Preliminary studies indicate that delamination of filament layers occurs at elevated temperatures, as opposed to thermo-hygral spalling, which typically occurs in conventionally cast high-performance concrete samples. Brittle structural failure may therefore occur du...
Article
While interest in 3D printing of concrete (3DCP) and structures has been growing, a major obstacle for implementation of 3DP construction method is the need for steel reinforcement and the challenges this presents to the 3DP process. Engineered Cementitious Composites (ECC), also known as Strain-hardening Cement-based Composites (SHCC), hold promis...
Article
3D printing of concrete (3DPC) is an automated layer-wise construction technique that does not require temporary support, such as formwork, during the construction process. It facilitates the realization of geometrically complex objects at reduced construction time, and potentially cost, compared to conventional construction techniques. However, wi...
Article
This research presents the development and application of a constructability design model, which determines the print speed and filament layer height combination that yields the fastest vertical building rate, whilst ensuring for the successful construction of an object. A 3D concrete printed structural wall element is used to validate the model. H...
Chapter
Lightweight foam concrete (LWFC) has relatively high workability, or low static and dynamic shear resistance in the fresh state. It is also sensitive to applied pressure. These limitations present challenges for 3D printing of LWFC, through its pumping and extrusion, and bearing pressure of subsequent layers. The associated risks of 3D printing LWF...
Chapter
3D printing of concrete (3DPC) is a developing automation technology that can promote further industrialisation in the construction industry. 3DPC has complex rheological requirements, namely low material viscosity for ease of pumping but high viscosity for constructability. Greater emphasis is therefore placed on the rheology of cement-based compo...
Thesis
Full-text available
Three industrial revolutions have occurred in the last 250 years that resulted in increased productivity for most economic sectors. This generally improved the standard of living for all individuals. Recent research has however found that the productivity of the USA’s construction sector regressed at 0.6 % per year over the last 55 years. This indi...
Article
Full-text available
Digital Construction presents opportunity for the rejuvenation of the construction industry as an industry of choice. In a research and education environment, this is visible in the technologically-minded graduates that are drawn to 3D concrete printing research. The particular setting in South Africa, with unemployment rate over 29% in a period of...
Conference Paper
Full-text available
The use of concrete as construction and building material has enormously increased in the last decades. Innovations in the concrete industry are asking for answers in terms of reusing construction demolishing waste, energy saving concepts and cost-effective solutions for CO2 reductions. Therefore, the concrete industry has committed itself towards...
Article
Full-text available
Growing interest in additive manufacturing in the construction industry has promoted research in 3D printing of concrete. A gantry-type 3D printer for concrete was designed and manufactured at the Department of Civil Engineering, Stellenbosch University. Characteristics of 3D printable concrete are investigated and reported. In the fresh state, thi...
Conference Paper
Full-text available
3D printing of concrete (3DPC) is a lineage technology of additive manufacturing (AM) that has transitioned from early industrial applications in the aerospace, medical and automobile sectors to recent explorations in academia and the construction industry. Recent interest in 3DPC can be ascribed to its compar- ative advantage regarding cost, mater...
Article
Contrary to the extensive literature available on the axial pull-out behavior of individual steel fibers embedded in a cement-based matrix, including different fiber orientations, limited research has been performed which characterizes the transverse pull-out response. The Ohno-beam shear test method, which to the authors' knowledge has not yet bee...
Conference Paper
Lightweight foam concrete (LWFC) has relatively high workability, or low static and dynamic shear resistance in the fresh state. It is also sensitive to applied pressure. These limitations present challenges for 3D printing of LWFC, through its pumping and extrusion, and bearing pressure of subsequent layers. The associated risks of 3D printing LWF...
Conference Paper
3D printing of concrete (3DPC) is a developing automation technology that can promote further industrialisation in the construction industry. 3DPC has complex rheological requirements, namely low material viscosity for ease of pumping but high viscosity for constructability. Greater emphasis is therefore placed on the rheology of cement-based compo...
Article
Alkali Silica Reaction (ASR) is a long term chemical reaction causes swelling and damage to the concrete material in the form of cracking and material deterioration. In this research a chemo-thermo-mechanical ASR finite element numerical code is developed to model and analyse this phenomenon in concrete dams. It considers the effects of variables s...
Article
This paper presents a novel rheological thixotropy model that specifically appertains to the characterisation of materials that are suitable for 3D printing of concrete (3DPC). The model accounts for both physical and chemical influences on a material's microstructure, denoted by R_thix (re-flocculation) and A_thix (structuration) respectively. Rhe...
Article
Concrete structures are 3D printed in the plastic state, therefore emphasis should be placed on the rheological characterisation of these materials to ensure that they are appropriate for 3D printing as well as for quality control. In this research, an analytical model based on the novel rheological characterisation of a material is presented as a...
Conference Paper
Lightweight foam concrete (LWFC) is becoming an interesting structural material. In its fresh state, LWFC is highly flowable. Modification of the rheology is required to include 3D construction printing as a production process for this class of materials. Nanoparticles have been shown to improve thixotropy of cement-based materials, characterized b...
Conference Paper
In South Africa there are many low-rise, unreinforced, load-bearing masonry (ULM) buildings in seismic zones due to shortcomings in South Africa s design codes. These buildings pose a great risk to their occupants in the case of seismic activity. A possible solution is to retrofit these buildings with a strain-hardening cement-based composite (SHCC...
Conference Paper
Full-text available
Academia and industry lack unified test methods to quantify the buildability of 3D printable concrete (3DPC). This study proposes benchmark structures to assess the buildability of a 3DPC. The benchmark structures quantify the capacity of a cement-based material to maintain sufficient stability and shape-retention under a reasonable wall gradient a...
Article
Durability of reinforced concrete (RC) is influenced by cracks, providing paths for ingress of corrosion agents and early corrosion initiation. The corrosion propagation stage has in recent years been the focus of investigation, however, mainly focused on a single crack and reinforcement bar. This study focuses on chloride‐induced corrosion in thre...
Conference Paper
Full-text available
The development of high-performance concrete (HPC) suitable for 3D printing is restricted by the fresh state of concrete i.e. a narrow workability concrete range that will yield appropriate printability and buildability. Thus, the main focus is to first obtain sufficient concrete rheology, followed by enhanced mechanical characteristics in the hard...
Article
Evaluation of the seismic performance of infill frame structural systems using equivalent strut models and pushover analysis has gained popularity due to the simplicity of the evaluation process. Various strut macromodels have been developed for both static and dynamic evaluation of the behavior of the infill frames when subjected to seismic loadin...
Article
Retrofitting of unreinforced load bearing masonry (ULM) in seismic regions has received significant attention, motivated by the substantial stock of ULM buildings and their vulnerability in seismic action. Sprayed application of a thin overlay of strain-hardening cement-based composite (SHCC) has been developed, and showed to significantly improve...
Article
Structural performance of both new and existing building structures under seismic actions can be assessed with a wide range of nonlinear static procedures and time history dynamic analysis available in literature. Most of these procedures, such as time history dynamic analysis, are complex as they require sophisticated finite element modelling. Rei...
Conference Paper
Full-text available
A research program on 3D printing of cement-based construction materials (3DPC) has been launched at Stellenbosch University. A versatile gantry type laboratory printer is designed and constructed, to enable fundamental research towards material and structural characterisation, development and design. A static yield shear stress evolution model for...
Conference Paper
The Kleinplaas dam, located on the Jonkershoek River near Stellenbosch in the Western Cape province of South Africa has been affected by Alkali Silica Reaction (ASR) for some years after its construction in 1982. Several important factors govern the ASR reaction kinetics, of which the moisture content of and temperature gradient in the concrete are...
Conference Paper
The rise of energy compliance has led to various countries adopting building rating systems as well as design codes that focus on energy efficiency. Although these codes and rating systems specify which targets should be met, little to no guidance is given on how to achieve these targets. Studies have shown that the building envelope accounts for t...
Article
Strengthening of unreinforced masonry walls is realised by a bonded overlay of strain-hardening cement-based composite. In-plane shearing resistance is considered here, although out-of-plane resistance is also increased by the overlay. The strain-hardening cement-based composite mix is adjusted for sprayed application with low run-off and waste. Ch...
Conference Paper
A 3D concrete printer has been designed and built by the authors to enable research on a range of concrete and fibre concrete materials. A range of cement-based materials are developed in order to determine the appropriate rheology for 3D printing of concrete (3DPC). Particular attention is paid to thixotropic behaviour. The viscosity of stiff, dou...
Conference Paper
Full-text available
Ingress Potential Indices (IPI) based on crack width distributions have recently been proposed for water permeation and chloride diffusion into cracked SHCC. Reasonable correlation between chloride content and the IPICl index has been reported, based on chloride profiles determined for multiply cracked R/SHCC beams. In these beams, significant conc...