TY - JOUR A1 - Kossatz, Philipp A1 - Mezhov, Alexander A1 - Andresen, Elina A1 - Schmidt, Wolfram A1 - Resch-Genger, Ute T1 - Application of fluorescence spectroscopy for the monitoring of cement hydration N2 - Lanthanide-based upconversion nanoparticles (UCNPs) with size- and morphology-dependent emission patterns, composed of narrow bands of varying intensity in the ultraviolet, visible, near-infrared, and short-wave infrared wavelength region, were synthesized via a thermal decomposition approach under inert atmosphere. Subsequently, differently sized UCNPs were incorporated into ordinary Portland cement to study their stability in the harsh cementitious environment and assess their potential for the probing and monitoring of cement hydration. Microenvironment-specific changes in the emission properties of these inorganic luminophores were utilized to study and probe changes of physico-chemical parameters during cement hydration. Isothermal calorimetry was employed to better understand the influence of luminophore addition on cement hydration kinetics and for the correlation with the results of the optical studies. T2 - 12th ACI/RILEM International Conference on Cementitious Materials and Alternative Binders for Sustainable Concrete (ICCM 2024) CY - Toulouse, France DA - 23.06.2024 KW - Luminescence KW - Optical probe KW - Cement hydration PY - 2024 UR - https://www.iccm2024.com/ SP - 441 EP - 446 CY - Toulouse, France AN - OPUS4-62119 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Kruschwitz, Sabine A1 - Munsch, Sarah Mandy A1 - Telong, Melissa A1 - Schmidt, Wolfram A1 - Bintz, Thilo A1 - Fladt, Matthias A1 - Stelzner, Ludwig T1 - The NMR core analyzing TOMograph: A multi-functional tool for non-destructive testing of building materials N2 - NMR is becoming increasingly popular for the investigation of building materials as it is a non-invasive technology that does not require any sample preparation nor causes damage to the material. Depending on the specific application it can offer insights into properties like porosity and spatial saturation degree as well as pore structure. Moreover it enables the determination of moisture transport properties and the (re-)distribution of internal moisture into different reservoirs or chemical phases upon damage and curing. However, as yet most investigations were carried out using devices originally either designed for geophysical applications or the analysis of rather homogeneous small scale (< 10 mL) samples. This paper describes the capabilities of an NMR tomograph, which has been specifically optimized for the investigation of larger, heterogeneous building material samples (diameters of up to 72 mm, length of up to 700 mm) with a high flexibility due to interchangeable coils allowing for a high SNR and short echo times (50 - 80 m s). KW - Fire spalling KW - Moisture transport KW - Concrete KW - Cement hydration KW - Sensitivity KW - Supplementary cementitous materials KW - Frost salt attack PY - 2023 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-573755 DO - https://doi.org/10.1016/j.mrl.2023.03.004 SN - 2097-0048 VL - 3 IS - 3 SP - 207 EP - 219 PB - Elsevier B.V. AN - OPUS4-57375 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Zhang, K. A1 - Mezhov, Alexander A1 - Schmidt, Wolfram T1 - Effect of Polycarboxylate Superplasticizer in Ordinary Portland Cement and Sulfate Resistant Cement N2 - Polycarboxylate superplasticizers (PCE) are the most widely used admixtures in today’s cementitious construction materials. The molecular structure has a decisive influence on the effectiveness of PCE, which also can be tailored to serve in a different cementitious system. The current study investigates the influence of the backbone charge density of PCE on the rheology, hydration kinetics, and adsorption behavior of ordinary Portland cement (OPC) and sulfate-resistant cement (SRC). The results indicate that regardless of the PCE type, OPC requires a higher amount of PCE to be adsorbed to induce changing of rheological parameters and hydration kinetics. Regardless of the cement type, the PCE with a higher charge density exhibits higher adsorption behavior, corresponding to lower viscosity measurement. Compared to OPC, SRC is more sensitive to the introduction of both PCEs and has a lower saturation dosage, indicating that SRC generally provides better workability properties regardless of the PCE. KW - Polycarboxylate superplasticizers (PCE) KW - Sulfate resistant cement (SRC) KW - Rheological KW - Adsorption KW - Cement hydration PY - 2023 DO - https://doi.org/10.1061/JMCEE7.MTENG-15033 SN - 0899-1561 VL - 35 IS - 6 SP - 1 EP - 12 PB - ASCE Libary AN - OPUS4-58244 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Zhang, Kun A1 - Kong, Deyu A1 - Schmidt, Wolfram A1 - Mezhov, Alexander T1 - Influence of hydroxypropylation of starch on rheological properties of cement paste modified by superplasticizers N2 - Starch is often used as a viscosity modifying agent (VMA) in self-compacting concrete (SCC) and highly flowable concrete. In this paper, starches possessing different degrees of hydroxypropyl substitution (DS) were used to study the shear rheological properties and hydration kinetics of cement paste in the presence of and without polycarboxylate superplasticizer (PCE). The starch with the highest DS increases the yield stress and the plastic viscosity stronger than others. Regardless of the dosage and DS of starch the structural build-up is not affected specifically by the starch during the induction period. During the acceleration period starches reduce the structural build-up, but with the highest DS this effect was less prominent than for the other modifications. In the presence of PCE the addition of starch notably increases the yield stress, whereas the influence on the plastic viscosity is limited. Yet, the combined application of PCE and starch allows to control rheological properties and maintain the structural build-up rate. KW - Modified starch KW - PCE KW - Structural build-up KW - Rheological properties KW - Cement hydration PY - 2025 DO - https://doi.org/10.1016/j.conbuildmat.2025.143646 SN - 1879-0526 VL - 495 SP - 1 EP - 13 PB - Elsevier CY - Amsterdam AN - OPUS4-64168 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Zhang, K. A1 - Schmidt, Wolfram A1 - Mezhov, Alexander T1 - Influence of the hydroxypropylation of starch on its performance as viscosity modifying agent N2 - Synopsis: Starch is a commonly used viscosity modifying agent (VMA). The performance of starch as VMA depends on its origin (e.g. potato, corn, cassava, etc.) and corresponding molecular properties, such as molecular weight, ratio between amylose and amylopectin etc. Depending upon the application, the efficiency of starch can be enhanced by hydroxypropylation. The maximum degree of substitution (DoS) cannot be greater than 3.0, which is the number of hydroxy groups per glucose monomer in the polymer. In the current research three potato starches exhibiting the DoS of 0.4, 0.6 and 0.8 were utilised. The influence of the modified starch on the rheological properties and hydration of cement paste, as well as the viscosity of the pore solution were investigated. Our findings show that the starch with the highest DoS increases the dynamic yield stress the most, while the plastic viscosity is less dependent on the DoS. Additionally, starch with the highest DoS retards hydration to lower degree than other starches. T2 - 13th International Conference on Superplasticizers and Other Chemical Admixtures in Concrete CY - Milan, Italy DA - 10.07.2022 KW - Potato starch KW - Rheological KW - Cement hydration KW - Pore solutions PY - 2022 DO - https://doi.org/10.14359/51736074 VL - 354 SP - 209 EP - 218 PB - ACI Special Publications AN - OPUS4-58320 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -