FG Baustoffe und Bauchemie

47 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...

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...

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...

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...

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...

The effects of calcium–silicate–hydrate (C–S–H) seeds on reference microorganisms

Augustyniak, Adrian ; Sikora, Pawel ; Jablonska, Joanna ; Cendrowski, Krzysztof ; John, Elisabeth ; Stephan, Dietmar ; Mijowska, Ewa (2020-03-21)

Building materials are constantly improved with various additives and admixtures in order to achieve goals ranging from obtaining increased durability or antimicrobial activity up to reducing the carbon footprint left by the cement production. Since nanomaterials were proposed for cement products, many studies explored the possibilities for their incorporation. One of the novel trends in studyi...

Testing of Eluates from Waterproof Building Materials for Potential Environmental Effects Due to the Behavior of Enchytraeus albidus

von Wolff, Marya Anne ; Pflugmacher, Stephan ; Stephan, Dietmar (2021-01-08)

In order to determine the potential environmental impact of construction products, it is necessary to evaluate their influence on organisms exposed to them or their eluates under environmental conditions. The behavior of the white worm Enchytraeus albidus is a useful tool for assessing the potential environmental impact of construction products in contact with water and soil. This study investi...

Effect of different expanded aggregates on durability-related characteristics of lightweight aggregate concrete

Chung, Sang-Yeop ; Sikora, Pawel ; Kim, Dong Joo ; El Madawy, Mohamed E. ; Abd Elrahman, Mohamed (2021-01-23)

Lightweight aggregate concrete (LWAC) has relatively larger porosity than conventional concrete, mainly due to the incorporation of porous lightweight aggregates. The types of used lightweight aggregates are critical in determining the physical properties of LWAC, and it is therefore important to examine their effects on the durable characteristics of the material. To perform comparative analys...

The effects of seawater and nanosilica on the performance of blended cements and composites

Sikora, Pawel ; Lootens, Didier ; Liard, Maxime ; Stephan, Dietmar (2020-03-09)

This study investigates the effects of seawater and nanosilica (3% by weight of cement), on the fresh and hardened properties of cement pastes and mortars produced with two types of low heat cements: Portland pozzolana cement (CEM II) and blast furnace cement (CEM III). The heat of hydration, initial and final setting times, rheological properties, strength development, sorptivity and water acc...

Comparison of the pore size distributions of concretes with different air-entraining admixture dosages using 2D and 3D imaging approaches

Chung, Sang-Yeop ; Sikora, Pawel ; Rucinska, Teresa ; Stephan, Dietmar ; Elrahman, Mohamed Abd (2020-02-06)

This study aims to more accurately investigate the pore size distribution of air voids in cement-based materials. For this purpose, micro-computed tomography (micro-CT) images were used to describe the inner structure of target materials, without damaging them. Together with the data obtained and the imaging techniques used, the pore structures of the specimens were visualized in 3D, with the p...

Evaluating the effects of nanosilica on the material properties of lightweight and ultra-lightweight concrete using image-based approaches

Sikora, Pawel ; Rucinska, Teresa ; Stephan, Dietmar ; Chung, Sang-Yeop ; Elrahman, Mohamed Abd (2020-07-30)

This work is aimed at characterizing the effects of nanosilica (NS) on the properties of lightweight aggregate concretes with different densities. Lightweight aggregate concrete (LWAC) and ultra-lightweight aggregate concrete (ULWAC) with targeted oven-dry densities of 850 kg/m3 and 450 kg/m3, respectively, were produced. The mixtures were modified by replacing cement with nanosilica, in concen...

Biocarbonation: a novel method for synthesizing nano-zinc/zirconium carbonates and oxides

Abdel-Gawwad, Hamdy A. ; Saleh, Alaa A. ; Sikora, Pawel ; Elrahman, Mohamed Abd ; Mohammed, Mona S. ; Hussein, Hala S. ; Ads, Essam Nabih (2020-10-01)

It is well known that the chemical precipitation is regarded as an effective approach for the preparation of nano-materials. Nevertheless, it represented several drawbacks, including high energy demand, high cost, and high toxicity. This work investigated the eco-sustainable application of plant-derived urease enzyme (PDUE)-urea mixture for synthesizing Zn–/Zr–carbonates and –oxides nanoparticl...

The Effects of Temperature Curing on the Strength Development, Transport Properties, and Freeze-Thaw Resistance of Blast Furnace Slag Cement Mortars Modified with Nanosilica

Federowicz, Karol ; Figueiredo, Vitoria Alves ; Al-kroom, Hussein ; Abdel-Gawwad, Hamdy A. ; Abd Elrahman, Mohamed ; Sikora, Pawel (2020-12-18)

This investigation studies the effects of hot water and hot air curing on the strength development, transport properties, and freeze-thaw resistance of mortars incorporating low-heat blast furnace slag cement and nanosilica (NS). Mortar samples were prepared and stored in ambient conditions for 24 h. After demolding, mortar samples were subjected to two different hot curing methods: Hot water a...