Inst. Bauingenieurwesen

230 Items

Recent Submissions
Analyzing the early structural build-up of accelerated cement pastes

Dorn, Tobias ; Hirsch, Tamino ; Stephan, Dietmar (2021-03-10)

Extrusion-based additive manufacturing imposes high requirements on the material stability right after the extrusion. Therefore, a thorough understanding of the chemical reactions that determine the early reduction in processability is necessary. Accelerators are especially considered here, which have a major influence on the early reaction. This study contributes to these issues by analyzing t...

3D printable lightweight cementitious composites with incorporated waste glass aggregates and expanded microspheres – Rheological, thermal and mechanical properties

Cuevas, Karla ; Chougan, Mehdi ; Martin, Falk ; Ghaffar, Seyed Hamidreza ; Stephan, Dietmar ; Sikora, Pawel (2021-05-15)

One of the fields in the construction industry where 3D printing of cementitious composites can play a significant role is associated with manufacturing of lightweight structures. Thanks to 3D printing, structural self-weight can be reduced by topology optimization of printed elements. Moreover, further decrements of self-weight and improvement of thermal insulating properties can be achieved b...

Dosing Free Nitrous Acid as an Alternative Sulphide Control Technology for Pressure Sewers in Germany

Despot, Daneish ; Reinhold, Luisa ; Augustyniak, Adrian ; Barjenbruch, Matthias (2021-04-08)

Sulphide build-up in pressure sewers has been identified as the main cause for the occurrence of odour and corrosion in sewer systems. Despite the efforts to optimize commonly used control technologies such as nitrate and iron salts to reduce sulphide emission, continuous addition of these chemicals is still required. A biocidal agent such as free nitrous acid can be added intermittently, less ...

The performance of ultra-lightweight foamed concrete incorporating nanosilica

Elrahman, Mohamed Abd ; Sikora, Pawel ; Chung, Sang-Yeop ; Stephan, Dietmar (2021-04-29)

This paper aims to investigate the feasibility of the incorporation of nanosilica (NS) in ultra-lightweight foamed concrete (ULFC), with an oven-dry density of 350 kg/m3, in regard to its fresh and hardened characteristics. The performance of various dosages of NS, up to 10 wt.-%, were examined. In addition, fly ash and silica fume were used as cement replacing materials, to compare their influ...

High‐resolution integrated transport model for studying surface water–groundwater interaction

Broecker, Tabea ; Gollo, Vahid Sobhi ; Fox, Aryeh ; Lewandowski, Jörg ; Nützmann, Gunnar ; Arnon, Shai ; Hinkelmann, Reinhard (2020-12-28)

Transport processes that lead to exchange of mass between surface water and groundwater play a significant role for the ecological functioning of aquatic systems, for hydrological processes and for biogeochemical transformations. In this study, we present a novel integral modeling approach for flow and transport at the sediment–water interface. The model allows us to simultaneously simulate tur...

High-resolution integral modelling approach for flow and transport in groundwater-surface water interaction space

Broecker, Katrin Tabea Christina (2021)

While former research studies mainly considered groundwater and surface water separately, the importance of their interactions is nowadays widely acknowledged. Especially the hyporheic zone, which is the zone where stream and shallow groundwater exchange, is addressed in many investigations. This zone is recognized for retention, transformation and attenuation of solutes and enables to improve ...

Ignition delay and chemical–kinetic modeling of undiluted mixtures in a high‐pressure shock tube: Nonideal effects and comparative uncertainty analysis

Zander, Lisa ; Vinkeloe, Johann ; Djordjevic, Neda (2021-01-21)

High‐pressure shock tube ignition delay data are essential for fuel characterization and for the validation and optimization of chemical–kinetic models. Therefore, it is crucial that realistic measurement conditions are considered in modeling. Furthermore, an accurate uncertainty quantification for experimental data is the basis for evaluation of the predictive reliability of chemical–kinetic m...

Supporting the Last Planner System with 4D BIM

Ortenburger, Selin ; Hartmann, Timo (2021-04)

Both Building Information Modeling (BIM) and Lean Construction are able to optimize the scheduling efficiency of a project by using a BIM 4D model or the Last Planner® System (LPS) which is a scheduling tool for Lean Construction. So far both methods have mainly been implemented separately, even though both share many similar aspects. This paper reports on a retrospective study of a recent proj...

The effects of nano- and micro-sized additives on 3D printable cementitious and alkali-activated composites: a review

Sikora, Pawel ; Chougan, Mehdi ; Cuevas, Karla ; Liebscher, Marco ; Mechtcherine, Viktor ; Ghaffar, Seyed Hamidreza ; Liard, Maxime ; Lootens, Didier ; Krivenko, Pavel ; Sanytsky, Myroslav ; Stephan, Dietmar (2021-02-27)

Additive manufacturing (AM), also referred as 3D printing, is a technology that enables building automated three-dimensional objects in a layer-by-layer manner. AM of cement-based and alkali-activated composites has gathered attention over the last decade and is one of the most rapidly developing civil engineering fields. Development of proper mixture compositions which are suitable in fresh an...

Investigating the release of ZnO nanoparticles from cement mortars on microbiological models

Augustyniak, Adrian ; Jablonska, Joanna ; Cendrowski, Krzysztof ; Głowacka, Anna ; Stephan, Dietmar ; Mijowska, Ewa ; Sikora, Pawel (2021-02-05)

Incorporating zinc oxide nanoparticles (ZnO NPs) into cement mortars may provide additional functions, e.g., self-cleaning and antibacterial or electroconductive ability. However, these NPs are also known for their potential toxicity. During the life cycle of a cement mortar, various abrasive forces cause the release of admixtures to the natural environment. The effect of the released NPs on mo...

Mapping the use of planning support in a strategy-making session

Champlin, Carissa ; Hartmann, Timo ; Dewulf, Geert P. M. R. (2018)

This paper introduces an alternative means of evaluating the performance of planning support systems. These systems that were originally developed to support the professional tasks of planners have been assessed primarily based on their task-technology-user fit. During the tasks of early planning phases, planning actors attempt to adapt planning issues out of their ‘wicked’ state and into clear...

Wissensintegrierende Modellierung der Geometrie von Bauwerken mit Intervallen und Constraints für Parameter

Kirchner, Jakob Vinzenz (2021)

Digitale Bauwerksmodelle stehen im Zentrum der modellbasierten Arbeitsweise in den Prozessen der Planung und Bewirtschaftung von Bauwerken. Sie bestehen dabei aus Daten, die semantische, geometrische und andere Aspekte des repräsentierten Bauwerks abbilden und algorithmisch nutzbar machen. Aktuelle Softwareprodukte ermöglichen zwar das Erstellen von Bauwerksmodellen, erfordern aber bei nachträg...

Thermal performance of building envelopes with structural layers of the same density: Lightweight aggregate concrete versus foamed concrete

Strzałkowski, Jarosław ; Sikora, Pawel ; Chung, Sang-Yeop ; Abd Elrahman, Mohamed (2021-03-15)

This study presents a comparative analysis of the effects of lightweight aggregate concrete (LWAC) and foamed concrete (FC), with dry densities of 500, 750 and 1000 kg/m3, on the thermal performance of a typical multi-family (residential) building. Typical two-layer walls consisting of an essential layer (LWAC or FC), with an insulating layer of foamed polystyrene were evaluated. To ensure fixe...

Emerging Leadership Roles in Collaborative Engineering Sessions

Bagenholm, David ; Hartmann, Timo (2021-03)

Purpose: To deal with the rising complexity of civil engineering projects, practice starts relying increasingly on collaborative design meetings. Leadership behaviour in such meeting is not yet well understood despite the importance of such understanding to manage collaborative design meetings well. The purpose of this study is to explore emerging leadership behaviour in design meetings through...

Phase and dimensional stability of volcanic ash-based phosphate inorganic polymers at elevated temperatures

Djobo, Jean Noël Yankwa ; Elimbi, Antoine ; Stephan, Dietmar (2020-04-06)

Phosphate geopolymers are part of chemically bonded phosphate cements obtained from an aluminosilicate and phosphate solution. Their structure consisting of phosphate bonds makes them suitable for use as refractory material. This study deals with the influence of phosphoric acid concentration (6, 8 and 10 mol/L) on the stability of volcanic ash-based phosphate geopolymers exposed to 100, 600 an...

Evaluation of the effects of bismuth oxide (Bi2O3) micro and nanoparticles on the mechanical, microstructural and γ-ray/neutron shielding properties of Portland cement pastes

Sikora, Pawel ; El-Khayatt, Ahmed M. ; Saudi, H.A. ; Chung, Sang-Yeop ; Stephan, Dietmar ; Elrahman, Mohamed Abd (2021-03-06)

This study presents a comparison of the effects of micro-Bi2O3 and nano-Bi2O3 powders on the mechanical, microstructural and gamma / neutron shielding properties of Portland cement pastes. Cement pastes with various ratios of cement (up to 30 wt-%) replaced with Bi2O3 micro and nanoparticles were prepared. Consistency, compressive strength, water accessible porosity and mercury intrusion porosi...

Investigation of additive incorporation on rheological, microstructural and mechanical properties of 3D printable alkali-activated materials

Chougan, Mehdi ; Ghaffar, Seyed Hamidreza ; Sikora, Pawel ; Chung, Sang-Yeop ; Rucinska, Teresa ; Stephan, Dietmar ; Albar, Abdulrahman ; Swash, Mohammad Rafiq (2021-02-10)

This study investigates the addition of Poly-vinyl Alcohol (PVA) fibres and attapulgite nanoclay to alkali-activated materials (AAMs) with the aim of enhancing the mechanical performance and optimizing the printability and buildability of AAMs. The fresh properties of six mix formulations, including flowability, slump values, rheology, shape retention, and extrusion window, were evaluated. The ...

The effects of nanosilica on the fresh and hardened properties of 3D printable mortars

Sikora, Pawel ; Chung, Sang-Yeop ; Liard, Maxime ; Lootens, Didier ; Dorn, Tobias ; Kamm, Paul H. ; Stephan, Dietmar ; Elrahman, Mohamed Abd (2021-02-19)

This study presents the experimental results of an investigation on the effects of nanosilica (NS) on the material characteristics of printable mortars used for additive manufacturing. Printable cement mortars based on Ordinary Portland Cement, limestone filler and silica sand were modified with different dosages of nanosilica (from 2% to 6% by weight of binder) and its influence on their hydra...

Comparison of lightweight aggregate and foamed concrete with the same density level using image-based characterizations

Chung, Sang-Yeop ; Elrahman, Mohamed Abd ; Kim, Ji-Su ; Han, Tong-Seok ; Stephan, Dietmar ; Sikora, Pawel (2019-03-30)

Lightweight concrete is a special type of concrete with low density and advanced insulation, mainly produced using lightweight aggregates or a cellular matrix. Concrete material made of lightweight aggregates is called lightweight aggregate concrete, while material made from a cellular matrix is generally called foamed concrete because of the pores introduced by a foaming agent. Both lightweigh...

The effects of seawater on the hydration, microstructure and strength development of Portland cement pastes incorporating colloidal silica

Sikora, Pawel ; Cendrowski, Krzysztof ; Elrahman, Mohamed Abd ; Chung, Sang-Yeop ; Mijowska, Ewa ; Stephan, Dietmar (2019-03-04)

This contribution investigates the effects of seawater and colloidal silica (NS) in the amounts of 1, 3 and 5 wt%, respectively, on the hydration, strength development and microstructural properties of Portland cement pastes. The data reveal that seawater has an accelerating effect on cement hydration and thus a significant contribution to early strength development was observed. The beneficial...