TY - CONF A1 - Ramirez Caro, Alejandra T1 - A spectroscopic study of the superplasticizer effect on early cement hydration N2 - Besides their plasticizing effect, superplasticizers (SPs) are known to retard the hydration of inorganic systems such as cement. Despite their frequent use, the understanding of these highly complex systems is still limited and the relevant parameters, which control the interaction between SPs, and cement components and reaction products are in the focus of ongoing research activities.[1] Optical methods have been successfully used for the analysis and monitoring of the interactions between a broad variety of nanoscale and molecular systems like nanoparticles of various chemical composition and different types of organic ligands or biomolecules. The potential of these methods to study processes at the interface between (hydrated) particles and the fluid phase at a very early stage of concrete formation could reveal possible mechanisms of interaction. This investigation focuses on the study of organic/inorganic mixtures consisting of cement (CEM) and cement phases (C3S and C3A) in the presence of polycarboxylate ether and organic dyes in aqueous solution (particularly alkali resistant dyes) at a water to powder ratio of 1. Diffuse reflectance as well as steady state and time resolved fluorescence spectroscopy of the above mentioned mixtures were evaluated. Based upon changes of the intensity of the reflectance and fluorescence signal and spectral changes of the dye, acting as optical reporter, a model for the interactions of dye, PCE and cement (including different cement phases) was derived which describes the very first stage of cement hydration. T2 - 2nd International Conference on Polycarboxylate Superplasticizers CY - München, Germany DA - 27.09.2017 KW - Cement KW - Superplasticizers KW - Dyes KW - Spectroscopy PY - 2017 AN - OPUS4-43365 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Ramirez Caro, Alejandra A1 - Pauli, Jutta T1 - Study of the hydration of superplasticizer-cement pastes with optical spectroscopy N2 - Chemical admixtures like superplasticizers or stabilizing agents are of ever increasing importance for modern concrete technology. Although such admixtures have meanwhile become common practice in many applications of concrete technology, the understanding of these highly complex systems is still limited and the relevant parameters, which predominantly control the interaction between the superplasticizer and the cement components, have not been identified yet. Optical methods have been successfully used for the analysis and monitoring of the interactions between a broad variety of nanoscale and molecular systems like nanoparticles of various chemical composition and different types of organic ligands or biomolecules. This encouraged us to assess the potential of these methods, and particularly reflectance and fluorescence measurements, for the study of the interactions that occur at the interface between particle or hydrate surfaces and the fluid phase at a very early stage of concrete formation. Special emphasis is dedicated to search for and identify differences between commonly used superplasticizers. Here, we focus on hydration effects using commercial comb shape polycarboxylate ethers (PCEs) with different charge densities, which are known to allow a very low water/cement ratio (w/c of 0.20 or less) while maintaining good workability. Based upon changes of the intensity of the reflectance and fluorescence signal and spectral effects of a dye, acting as optical reporter, a model for the interactions of dye, PCE molecules and cement nanoparticles in the very first phase of cement hydration is derived T2 - Gesellschaft Deutscher Chemiker-Analytische Chemie-Anakon 2017 CY - Tübingen, Germany DA - 03.04.2017 KW - Cement hydration KW - Optical spectroscopy KW - Superplasticizers PY - 2017 AN - OPUS4-39882 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Ramirez Caro, Alejandra A1 - Pauli, Jutta T1 - Study of the superplasticizer-cement hydration interaction by optical spectroscopy N2 - Chemical admixtures like superplasticizers or stabilizing agents are of ever increasing importance for modern concrete technology. Although such admixtures have meanwhile become common practice in many applications of concrete technology, the understanding of these highly complex systems is still limited and the relevant parameters, which predominantly control the interaction between the superplasticizer and the cement components, have not been identified yet. Optical methods have been successfully used for the analysis and monitoring of the interactions between a broad variety of nanoscale and molecular systems like nanoparticles of various chemical composition and different types of organic ligands or biomolecules. This encouraged to assess the potential of these methods for the investigation of the interactions that occur at the interface between particle or hydrate surfaces and the fluid phase at a very early stage of concrete formation and to differentiate between different superplasticizer. T2 - 2. ICCCM CY - Munich, Germany DA - 10.10.2016 KW - Optical spectroscopy KW - Cement hydration PY - 2016 AN - OPUS4-38474 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Ramirez Caro, Alejandra T1 - The Effect of Low Charge Polycarboxylate on C3A Passivation Monitored by Optical Spectroscopy N2 - Tricalcium aluminate (C3A) is less than 10 wt.% of the total cement composition; however, during hydration, the soluble C3A plays an important role in cement setting when mixed with the appropriate amount of sulfate.1 A good understanding about the balance of these components is therefore crucial to follow with the rapid growth of substitution materials and the rising levels of aluminate clinker. The aim of this investigation is the use of optical spectroscopy and in-situ X-ray diffraction utilizing a water-soluble organic dye (dye-S) to monitor early hydration of calcium aluminate (C3A) in the presence of 26 wt.% CaS04.2H2O (G) and PCE polymers with different charge densities (PCE-LC and PCE-HC). Phase characterization and optical evaluation were performed using in-situ X-ray diffraction and steady-state fluorescence and diffuse reflectance spectroscopy. Fluorescence spectroscopy of the reference C3A + dye-S revealed a fast decay in fluorescence intensity. However, in the presence of 26 wt.% G (C3A + dye-S + 26 wt.% G), a gradual increase in fluorescence intensity was observed in the first hours of reaction followed by a plateau that subsequently dropped in intensity after eight hours. The addition of PCE-LC and PCE HC to the mixture exhibited changes in the intensity threshold and overall a higher fluorescence intensity. Dye changes during hydration and structural changes will be further discussed. T2 - 3rd International Conference on Polycarboxylate Superplasticizers (PCE 2019) CY - Munich, Germany DA - 23.10.2019 KW - Dye KW - C3A KW - Optical Spectroscopy KW - Gypsum PY - 2019 AN - OPUS4-49343 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Ramirez Caro, Alejandra T1 - Use of Optical Spectroscopy to Monitor Cement Hydration and Additive Effect N2 - Use of optical spectroscopy and fluorescence reporter (DFFL and dye-S) to visualize the effects of additives on the hydration of cement pastes as a fast, sensitive and monitoring method. T2 - Beirat Tagung CY - Berlin, Germany DA - 26.04.2019 KW - Cement KW - Optical Spectroscopy KW - Dye KW - Hydration KW - Superplasticizer PY - 2019 AN - OPUS4-49349 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -