HeidelbergCement Technology Center GmbH

Leimen, Germany

HeidelbergCement Technology Center GmbH

Leimen, Germany
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Zajac M.,HeidelbergCement Technology Center GmbH | Hoock S.,HeidelbergCement Technology Center GmbH | Hoock S.,Mannheim University of Applied Sciences | Stabler C.,HeidelbergCement Technology Center GmbH | Ben Haha M.,HeidelbergCement Technology Center GmbH
Cement and Concrete Research | Year: 2017

Four types of binders, based on the three different clinkers are investigated. These binders are of similar bulk chemical composition but contain different aluminate and silicate phases, which dissolve at different rates. The differences in reaction kinetics result in different phases assemblage at early ages. The phase assemblages tend to converge at later ages. Ettringite, AFm phases, C-S-H and strätlingite are the main hydrates. Their kinetics of formation and quantities depend on the dissolution rate of the anhydrous material. The differences in hydrates assemblage impact on the microstructures. Systems with ettringite or other crystalline hydrates as main hydration products at early ages, result in a coarser porosity. A refinement of the porosity is found in all the investigated samples with the ongoing formation of amorphous hydrates. Two mechanisms responsible for reduced hydration kinetics at later ages are identified: high Al concentration in the pore solution and dense microstructure. © 2017.


Adu-Amankwah S.,University of Leeds | Zajac M.,HeidelbergCement Technology Center GmbH | Stabler C.,HeidelbergCement Technology Center GmbH | Lothenbach B.,Empa - Swiss Federal Laboratories for Materials Science and Technology | Black L.,University of Leeds
Cement and Concrete Research | Year: 2017

The hydration kinetics, microstructure and pore solution composition of ternary slag-limestone cement have been investigated. Commercial CEM I 52.5 R was blended with slag and limestone; maintaining a clinker to SCM ratio of 50:50 with up to 20% slag replaced by limestone. The sulphate content was maintained at 3% in all composite systems. Hydration was followed by a combination of isothermal calorimetry, chemical shrinkage, scanning electron microscopy, and thermogravimetric analysis. The hydration of slag was also followed by SEM image analysis and the QXRD/PONKCS method. The accuracy of the calibrated PONKCS phase was assessed on slag and corundum mixes of varying ratios, at different water/solid ratios. Thus, the method was used to analyse hydrated cement without dehydrating the specimens. The results show that the presence of limestone enhanced both clinker and slag hydration. The pore volume and pore solution chemistry were further examined to clarify the synergistic effects. The nucleation effects account for enhanced clinker hydration while the space available for hydrate growth plus the lowering of the aluminium concentration in the pore solution led to the improved slag hydration. © 2017 Elsevier Ltd


Dauzeres A.,Institute for Radiological Protection and Nuclear Safety | Achiedo G.,Institute for Radiological Protection and Nuclear Safety | Nied D.,HeidelbergCement Technology Center GmbH | Bernard E.,Empa - Swiss Federal Laboratories for Materials Science and Technology | And 2 more authors.
Cement and Concrete Research | Year: 2016

In the framework of the CI project, the interaction of two different low-pH cements (ESDRED and LAC) with Opalinus Clay (OPA) at Mont-Terri rock laboratory was studied. SEM-EDS analyses showed after 2.5 and 5 years of interaction a Mg-enriched zone associated with a decalcification of the C-S-H near the OPA contact zone of both cements. TGA and XRD investigations indicate that hydrotalcite and brucite predict classically in modeling are not formed. 29Si NMR and FTIR analyses showing a high polymerization degree of the Si-network typical of a sheet-like structure as observed for M-S-H. TEM/EDS investigations of the Mg enriched zone of both concretes indicate that the formed Mg phase exhibits a gel-like structure. New reactive transport modeling with the HYTEC code corroborates the formation of M-S-H at the interface. © 2015 Elsevier Ltd.


Nied D.,HeidelbergCement Technology Center GmbH | Nied D.,Empa - Swiss Federal Laboratories for Materials Science and Technology | Enemark-Rasmussen K.,University of Aarhus | L'Hopital E.,Empa - Swiss Federal Laboratories for Materials Science and Technology | And 2 more authors.
Cement and Concrete Research | Year: 2016

Investigations of synthetic magnesium silicate hydrate (M-S-H) samples have shown that M-S-H aged for 1 year can exhibit variable compositions with molar Mg/Si ratios in the range 0.7 ≤ Mg/Si ≤ 1.5. At lower Mg/Si ratio, additional silica is present whereas brucite is observed for Mg/Si ≥ 1.3. FT-IR and 29Si NMR data reveal a high degree of silicate polymerisation, indicating the formation of silicate sheets. TGA shows the presence of bound water and of hydroxyl groups bound to Mg and as silanol groups in the M-S-H, in accord with 29Si{1H}CP/MAS and high-speed 1H NMR measurements. Raman and XRD data suggest that the M-S-H structure is related to a disordered talc precursor at low Mg/Si and to a serpentine precursor at high Mg/Si ratio. Solubility products for M-S-H phases were calculated on basis of the compositions of the aqueous solutions and a solid solution model was suggested. © 2015 Elsevier Ltd.


Wadso L.,Lund University | Arndt M.,HeidelbergCement Technology Center GmbH
Cement and Concrete Research | Year: 2016

The results of a round robin test on isothermal (heat conduction) calorimetry are presented. A total of 18 participants using three types of instruments conducted 3-day measurements of the hydration of one rapidly hardening Portland cement and one slag-containing cement. The results confirm that isothermal calorimetry is a suitable method for the determination of heat of hydration. As a part of the study, two laboratories also conducted measurements with the standardized heat of solution method. For the Portland cement, these results were in good agreement with the isothermal measurements, but for the slag-containing cement the results differed, both between the two laboratories and between their results and the result of isothermal calorimetry. However, this method performance study clearly shows that the heat of hydration determination of cement by heat conduction calorimetry is more precise than the traditional heat of solution method described in EN 196-8, if state-of-the-art calorimeters are used. © 2015 Elsevier Ltd.


Federhen S.,HeidelbergCement Technology Center GmbH
Cement International | Year: 2010

At HeidelbergCement many (chlorine) gas bypass systems have been installed in the recent years. The first solutions simply aimed at dedusting. Later, via adding hydrated lime, SOx was treated. Further steps were undertaken by adding raw meal to ease the dust handling. However, cost analysis showed that the most economic approach is SOx treatment by recycling the gas within the kiln system and reducing bypass dust disposal by homogenisation and pre-separation. The initial additional investment for the equipment was swiftly recovered due to reduced operational costs. Though the operation is challenging - it is manageable. Looking forward, the gas recycle back to the cooler and integral dust homogenisation are the dominant choice for the future.


Bolte G.,HeidelbergCementTechnology Center GmbH
Betonwerk und Fertigteil-Technik/Concrete Plant and Precast Technology | Year: 2013

Nitrogen oxides (NOX) are one of the most critical groups of air pollutants in the vicinity of major urban roads. One of the options to reduce the concentration of these pollutants in the air we breathe is to create photocatalytically active surfaces in appropriate locations. High-energy UV radiation triggers the formation of highly reactive compounds on the surface of such photocatalysts. These compounds have been shown to mineralize nitric oxide (NO) and nitrogen dioxide (NO2) present in the air, thus removing these substances from the air [1].


Zajac M.,HeidelbergCement Technology Center GmbH | Ben Haha M.,HeidelbergCement Technology Center GmbH
Materials and Structures/Materiaux et Constructions | Year: 2014

A systematic study on several mix designs has been carried out to correlate the microstructural properties, i.e. degree of hydration, C-S-H composition, capillary porosity to the mechanical properties, such as compressive strength and elastic modulus. For this purpose, thermodynamic modeling was used to calculate the type and amount of hydrates formed during ongoing hydration of ordinary Portland and blended fly ash cements. Obtained results of the phase development over the hydration time agree well with the measured amount of the phases. Additionally, by plotting the measured compressive strength versus the modeled porosity, a quasi-unique relationship for both, OPC and OPC blended systems, is obtained. This new finding gives further insights allowing us to develop a micromechanical model linking the mineralogical composition of anhydrous systems to corresponding mechanical properties. On the other hand, it provides a possibility to improve the composition of cementitious systems to improve their properties and performance. © 2013 RILEM.


Zajac M.,HeidelbergCement Technology Center GmbH | Rossberg A.,Empa - Swiss Federal Laboratories for Materials Science and Technology | Le Saout G.,Empa - Swiss Federal Laboratories for Materials Science and Technology | Lothenbach B.,Empa - Swiss Federal Laboratories for Materials Science and Technology
Cement and Concrete Composites | Year: 2014

The addition of CaCO3 and CaSO4 to Portland cement clinker influences the hydration and the strength development. An increase of the CaSO4 content accelerates alite reaction during the first days and results in the formation of more ettringite, thus in a higher early compressive strength. The late compressive strength is decreased in Portland cements containing higher quantities of CaSO4. The reduced late compressive strength seems to be related to an increase of the S/Si and Ca/Si content in the C-S-H. The presence of calcite leads to the formation of hemicarbonate and monocarbonate thus indirectly to more ettringite. Only a relatively small quantity of calcite reacts to form monocarbonate or hemicarbonate in Portland cement. Although hemicarbonate is thermodynamically less stable than monocarbonate, hemicarbonate formation is kinetically favored. Monocarbonate is present only after 1 week and longer independent of the quantity of calcite available and the content of sulphate in the cement. © 2013 Elsevier Ltd. All rights reserved.


Svec O.,Technical University of Denmark | Skocek J.,Technical University of Denmark | Skocek J.,HeidelbergCement Technology Center GmbH
Journal of Non-Newtonian Fluid Mechanics | Year: 2013

The ability of the Lattice Boltzmann method, as the fluid dynamics solver, to properly simulate macroscopic Navier's slip boundary condition is investigated. An approximate equation relating the Lattice Boltzmann variable slip boundary condition with the macroscopic Navier's slip boundary condition is proposed. The proposed relation is validated both for the case of Newtonian and non-Newtonian fluids. The importance of employing the Navier's slip boundary condition is highlighted by a practical industrial problem. © 2013 Elsevier B.V.

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