Viktor Mechtcherine

Bio: Viktor Mechtcherine is an academic researcher from Dresden University of Technology. The author has contributed to research in topics: Ultimate tensile strength & Materials science. The author has an hindex of 48, co-authored 278 publications receiving 7070 citations. Previous affiliations of Viktor Mechtcherine include Karlsruhe Institute of Technology & RWTH Aachen University.

Vision of 3D printing with concrete — Technical, economic and environmental potentials

Abstract: A vision is presented on 3D printing with concrete, considering technical, economic and environmental aspects. Although several showcases of 3D printed concrete structures are available worldwide, many challenges remain at the technical and processing level. Currently available high-performance cement-based materials cannot be directly 3D printed, because of inadequate rheological and stiffening properties. Active rheology control (ARC) and active stiffening control (ASC) will provide new ways of extending the material palette for 3D printing applications. From an economic point of view, digitally manufactured concrete (DFC) will induce changes in the stakeholders as well as in the cost structure. Although it is currently too ambitious to quantitatively present the cost structure, DFC presents many potential opportunities to increase cost-effectiveness of construction processes. The environmental impact of 3D printing with concrete has to be seen in relation to the shape complexity of the structure. Implementing structural optimization as well as functional hybridization as design strategies allows the use of material only where is structurally or functionally needed. This design optimization increases shape complexity, but also reduces material use in DFC. As a result, it is expected that for structures with the same functionality, DFC will environmentally perform better over the entire service life in comparison with conventionally produced concrete structures.

Dispersion of carbon nanotubes and its influence on the mechanical properties of the cement matrix

Abstract: An appropriate dispersion of carbon nanotubes (CNTs) is a prerequisite for their use in improving the mechanical properties of cement-based composites In this study two types of carbon nanotubes (CNTs) having different morphologies were investigated To obtain a uniform distribution of CNTs in the cement matrix, the effect of sonication on the deagglomeration of CNTs in combination with anionic and nonionic surfactants in varying concentrations was quantitatively investigated when preparing aqueous dispersions of CNTs for the subsequent use in cement paste The relationships between the quality of CNT-dispersion on the one hand and the sonication time and surfactant concentration on the other were determined using UV–vis spectroscopy After dispersion, nitrogen-doped CNTs were found mostly as individual, broken CNTs In contrast, after the treatment of the mixture of single-, double-, and multi-walled CNTs, a net-like distribution was observed where destruction of the CNTs due to sonication could not be distinguished Modification of the cement pastes with dispersions of CNTs led to a pronounced increase, up to 40%, in compressive strength and, in some cases, to a moderate increase in tensile strength under high strain-rate loading However, no significant improvement in strength was observed for quasi-static loading Microscopic examination revealed that the bridging of the C–S–H phases differed depending on the type of CNT This explained, at least partly, the observed effects of CNT-addition on the mechanical properties of hardened cement pastes

Relation between the molecular structure and the efficiency of superabsorbent polymers (SAP) as concrete admixture to mitigate autogenous shrinkage

Abstract: Superabsorbent polymers (SAP) were studied as admixtures for mitigating the autogenous shrinkage of a high-strength concrete. The presence of Ca 2+ ions in the alkaline solution modified the kinetics of the liquid uptake and release when compared to that in other saline solutions and distilled water. SAP with high density of anionic functional groups took up the cement pore solution quickly, but greatly released it subsequently. The cross-linking density had no pronounced influence on the behaviour of such SAP. SAP with lower density of anionic groups did not release the liquid over the time of experiment. All SAP counteracted autogenous shrinkage during the acceleration period of cement hydration. For the materials which released the absorbed pore solution no effect on autogenous shrinkage was found beyond the initial period. SAP materials which did not release the absorbed solution in the experiments with liquids continued the mitigation of autogenous shrinkage during the deceleration period. The internal curing had no negative effect on the compressive strength of the mortar.

Effects of layer-interface properties on mechanical performance of concrete elements produced by extrusion-based 3D-printing

Abstract: Interfaces between layers in 3D-printed elements produced by extrusion-based material deposition were investigated on both macro- and micro-scales. On the macro-scale, compression and flexural tests were performed on two 3D-printable cement-based compositions (3PCs), namely Mixtures C1 (with Portland cement as sole binder) and C2 (containing pozzolanic additives) at testing ages of 1 day and 28 days. The influences of binder composition and time interval between layers on layer-interface strength were critically analyzed. The investigated time intervals were 2 min, 10 min and 1 day. The investigations revealed that Mixture C2 exhibited lower degrees of anisotropy and heterogeneity as well as superior mechanical performance in comparison to Mixture 1. In particular, Mixture C2 showed a less pronounced (below 25%) decrease in interface bond strength as observed in flexural tests for all time intervals under investigation. In contrast, the decrease in flexural strength measured for C1 specimens amounted to over 90% due to the higher porosity at the interfaces of the printed concrete layers. Microscopic observations supported the findings of the macroscopic investigations. SEM images also delivered additional information on morphology of interfacial defects as well as “self-healing”.

Extrusion-based additive manufacturing with cement-based materials – Production steps, processes, and their underlying physics: A review

Abstract: This article offers a comprehensive overview of the underlying physics relevant to an understanding of materials processing during the various production steps in extrusion-based 3D concrete printing (3DCP). Understanding the physics governing the processes is an important step towards the purposeful design and optimization of 3DCP systems as well as their efficient and robust process control. For some processes, analytical formulas based on the relevant physics have already enabled reasonable predictions with respect to material flow behavior and buildability, especially in the case of relatively simple geometries. The existing research in the field was systematically compiled by the authors in the framework of the activities of the RILEM Technical Committee 276 “Digital fabrication with cement-based materials”. However, further research is needed to develop reliable tools for the quantitative analysis of the entire process chain. To achieve this, experimental efforts for the characterization of material properties need to go hand in hand with comprehensive numerical simulation.

American Society for Testing and Materials

Abstract: The American Society for Testing and Materials (ASTM) is an independent organization devoted to the development of standards.

Properties Of Concrete

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Wood-Derived Materials for Green Electronics, Biological Devices, and Energy Applications.

Abstract: With the arising of global climate change and resource shortage, in recent years, increased attention has been paid to environmentally friendly materials. Trees are sustainable and renewable materials, which give us shelter and oxygen and remove carbon dioxide from the atmosphere. Trees are a primary resource that human society depends upon every day, for example, homes, heating, furniture, and aircraft. Wood from trees gives us paper, cardboard, and medical supplies, thus impacting our homes, school, work, and play. All of the above-mentioned applications have been well developed over the past thousands of years. However, trees and wood have much more to offer us as advanced materials, impacting emerging high-tech fields, such as bioengineering, flexible electronics, and clean energy. Wood naturally has a hierarchical structure, composed of well-oriented microfibers and tracheids for water, ion, and oxygen transportation during metabolism. At higher magnification, the walls of fiber cells have an interes...

A review on basalt fibre and its composites

Abstract: In recent years, both industrial and academic world are focussing their attention toward the development of sustainable composites, reinforced with natural fibres. In particular, among the natural fibres (i.e. animal, vegetable or mineral) that can be used as reinforcement, the basalt ones represent the most interesting for their properties. The aim of this review is to illustrate the results of research on this topical subject. In the introduction, mechanical, thermal and chemical properties of basalt fibre have been reviewed. Moreover, its main manufacturing technologies have been described. Then, the effect of using this mineral fibre as reinforcement of different matrices as polymer (both thermoplastic and thermoset), metal and concrete has been presented. Furthermore, an overview on the application of this fibre in biodegradable matrix composites and in hybrid composites has been provided. Finally, the studies on the industrial applications of basalt fibre reinforced composites have been reviewed.