Markus Königsberger

• PhD
• PostDoc Position at Université Libre de Bruxelles

State-of-the-art workflows within Architecture, Engineering, and Construction (AEC) are still caught in sequential planning processes. Digital design tools in this domain often lack proper communication between different stages of design and relevant domain knowledge. Furthermore, decisions made in the early stages of design, where sketching is use...

This research examines the evolution of visco-elastic strains of sodium hydroxide-activated blast furnace slag mortar (with two different molarities of the activator solution) since the earliest age. Two distinct load durations, a short loading lasting five minutes is repeated hourly and a long loading lasting several weeks is applied on the aging...

Lignin, a main component of plants, is produced in large quantities as a by-product of the pulp and papermaking industry. The abundance of this organic polymer makes it an excellent candidate for developing renewable materials such as lignin-based biocomposites. The mechanical properties of lignin, as well as the dependence on the extraction proces...

The mechanical properties of natural fibers, as used to produce sustainable biocomposites, vary significantly-both among different plant species and also within a single species. All plants, however, share a common microstructural fingerprint. They are built up by only a handful of constituents, most importantly cellulose. Through continuum microme...

The stiffness of cementitious materials decreases with increasing temperature. Herein, macroscopic samples of mature cement pastes are subjected at 20, 30, and 45 °C, respectively, to three-minutes-long creep compression experiments. The test evaluation is based on the linear theory of viscoelasticity and Boltzmann’s superposition principle. This y...

The growing use of blends of low- and high-calcium solid precursors in combination with different alkaline activators requires simple, efficient, and accurate experimental means to characterize their behavior, particularly during the liquid-to-solid transition (setting) at early material ages. This research investigates slag-fly ash systems mixed a...

Replacing ordinary Portland cement-based materials with alkali-activated industrial wastes is often limited because of significant volume changes occurring in these materials at early age. This experimental study aims to quantify the extent of the volume changes and explore the underlying mechanisms of pastes composed of slag and fly ash (ratio 50:...

Fire tests on masonry are one of the most expensive experiments in developing new vertically perforated clay block geometries. Numerical simulations might be a reasonable substitute for such experiments, leading to a significant cost reduction in the development phase. However, the prediction of such tests with numerical modelling concepts is chall...

Given the popularity of fired clay bricks in increasingly taller buildings, as well as the large variety of raw materials, additives, tempers, and production technology, microstructure-based modeling of the brick strength is essential. This paper aims at linking the microstructural features of bricks, i.e. the volume, shape, and size of mineral pha...

Global warming and global scarcity of resources drive the need for optimization of industrial buildings. Theconstruction industry is one of the most resource-intensive economic sectors and at the same time belongsto most of the man-made raw material storage. To contribute to a resource-efficient future in theconstruction sector, a multi-objective o...

Quantification of elastic stiffness and thermal conductivity of fired clay bricks is still often limited to empirical rules and laboratory testing, which becomes progressively more challenging given the large variety of raw materials used to optimize the properties of modern brick products. Applying a continuum micromechanics multiscale approach, w...

The mechanical interactions of C-(N-)A-S-H (Calcium-sodium-aluminum-silicate-hydrate) gel with slag and fly ash inclusions in alkali-activated materials (AAM) are quantified through image-supported grid nanoindentation. Nonuniform distributions of indent-specific indentation properties reveal that the elasticity-related domain is up to 130 times th...

This paper presents the results of a European benchmark on multiscale creep modeling for cementitious materials, performed in the framework of the COST Action TU1404 “Towards the next generation of standards for service life of cement-based materials and structures”. Three micromechanical models from three research groups have been adopted for mode...

Modeling of the complex interlinked chemical reactions involved in the hydration process of slag-blended cement is rather challenging, in particular since accurate prediction of the hydration kinetics of clinker and slag hydration, respectively, is still out of reach. To overcome this challenge, we propose a hybrid modeling approach based on calori...

State-of-the-art micromechanical models for cement and concrete typically introduce two types of hydrate gel built up by single nanometer-sized solid calcium-silicate-hydrate (C-S-H) blocks and a constant gel porosity in between, in order to upscale nanoindentation-derived elastic properties of ”low density C-S-H gel” and ”high-density C-S-H gel” u...

Polymer-modified mortars and concretes are more creep active than conventional cement-based materials. The present contribution studies the effects of the polymer particles at microscopic observation scales and quantifies their viscoelastic properties during cement hydration. To this end, two different polymer-modified cement pastes were characteri...

Recycled concrete, i.e., concrete which contains aggregates that are obtained from crushing waste concrete, typically exhibits a smaller strength than conventional concretes. We herein decipher the origin and quantify the extent of the strength reduction by means of multiscale micromechanics-based modeling. Therefore, the microstructure of recycled...

Adding polymers to cementitious materials improves their workability and impermeability, but also increases their creep activity. In the present paper, the creep behavior of polymer-modified cement pastes is analyzed based on macroscopic creep tests and a multiscale model. The continuum micromechanics model allows for “downscaling” the results of m...

This paper presents the results of the numerical benchmark campaign on modelling of hydration and microstructure development of cementitious materials. This numerical benchmark was performed in the scope of COST Action TU1404 “Towards the next generation of standards for service life of cement-based materials and structures”. Seven modelling groups...

This paper presents the results of the numerical benchmark campaign on modelling of hydration and microstructure development of cementitious materials. This numerical benchmark was performed in the scope of COST Action TU1404 “Towards the next generation of standards for service life of cement-based materials and structures”. Seven modelling groups...

Ever since the early days of Féret (1892) and Abrams (1919), concrete research has targeted at relating concrete composition to uniaxial compressive strength. While these activities were mainly characterized by empirical fitting functions, we here take a more fundamental approach based on continuum micromechanics. The loading applied at the concret...

Introduction of infinitely many solid phases in continuum micromechanical representations of hierarchical porous media, in combination with rigorous consideration of free strains and stresses (which arise in the material microstructures as plastic or viscous strains, or as pore pressures) turned out as the major key to providing reliable (“nano-mic...

Creep of cementitious materials results from the viscoelastic behavior of the reaction products of cement and water, called hydrates. In the present paper, a single isochoric creep function characterizing well-saturated portland cement hydrates is identified through downscaling of 500 different nonaging creep functions derived from three-minute-lon...

NMR relaxometry (Muller et al., 2012, 2013) quantifies the mass fractions of differently bound water in cement paste, as functions of hydration degree and water-to-cement ratio. We here reduce these findings to a single explanation: the density of C-S-H gel is solely governed by the specific precipitation space, across three “hydration regimes”: In...

3min long creep tests are repeated hourly for cement paste, mortar and concrete exhibiting different water-to-cement ratios. Based on the results on the cement paste scale, the hydrate creep properties are identified by micromechanics modeling. Finally, the mortar and concrete creep behaviour is modeled by starting on the cement paste scale. This a...

C-S-H gel densifies progressively during hydration. Consideering that the available precipitation space may be the key parameter driving gel densification, we here use NMR relaxometry data in combination with basic stoichiometric relations of hydration chemistry, in order to develop a model for the evolution of C-S-H gel density as well as the phas...

A multiscale approach is presented which allows for upscaling the stiffness of the nanometer-sized solid C-S-H particles, which stems from statistical physics approaches, to the macroscopic stiffness of cement paste. Pore pressure-induced stiffening effects are qunatified.

Crack initiation in concrete, represents the elastic limit of the material, typically starting in the 15 microns thick interfacial transition zones (ITZs) around aggregates. Recently, two possible modes for crack initiation have been identified from inspection of post-failure concrete fragments: clean separation of aggregates from ITZs and ITZ crac...

Two failure modes in the ITZ around concrete aggregates are studied and compared by means of a micromechanical approach: a) tensile traction-induced separation of ITZ from aggregates, (b) tensile stress-induced failure of ITZs.

Cracking in concrete typically starts in the immediate vicinity around the aggregates, i.e., in the region of the so-called interfacial transition zones (ITZs), but the process is still not fully understood. Notably, crushing of concrete in compression results in fragments with interesting aggregate surface textures. Part of the aggregate surfaces...

At the macroscopic scale, concrete appears as a composite made of a cement paste matrix with embedded aggregates. The latter are covered by interfacial transition zones (ITZs) of reduced stiffness and strength. Cracking in the ITZs is probably the key to the nonlinear stress–strain behavior in the prepeak regime. For a deeper understanding of this...

Concrete aggregates are covered by 15-microns-thick interfacial transition zones (ITZs) exhibiting larger porosity, but smaller stiffness and strength than the adjacent bulk cement paste. This renders the immediate vicinities of the aggregates' surfaces as the weakest links within the microstructure of concrete. Onset of cracking, representing the...