TY - JOUR A1 - Cunningham, P. R. A1 - Mezhov, Alexander A1 - Schmidt, Wolfram T1 - Revealing Value from Bioderived Polymers: Effects of Locally Sourced Polysaccharides on the Rheology of Limestone Mixtures JF - Bio-Based Building Materials N2 - Admixtures are important constituents to enhance the performance of concrete. They allow for more efficient use of binders which can mitigate negative environmental impacts from producing cement-based materials. Commonly used rheology modifying agents like polycarboxylate ethers or cellulose ethers are synthetic or semi-synthetic, respectively. This requires additional energy consumption for their production and global supply chains particularly for many developing regions, which will be large consumers of concrete in the future. However, many locally available bio-based polysaccharides could be effectively used instead. These polymers are often overlooked by engineers and scientists due to their limited distribution and inherent complexity, yet they represent an underleveraged source of precursors for admixtures. This study investigates the action mechanisms of some bio-based rheology modifying agents, i.e., acacia gum and miscanthus gum, and provides a comparison to a conventionally modified starch. The results show that the mechanism of action of these polymers is closely related to the composition of the mixture, mixing regime, and the composition of the aqueous phase. Depending on the agent, either plasticizing or stabilizing effects on rheology can be revealed. T2 - ICBBM: International Conference on Bio-Based Building Materials CY - Vienna, Austria DA - 21.06.2023 KW - Polysaccharides KW - Superplasticizers KW - Hydration KW - Cement PY - 2023 DO - https://doi.org/10.1007/978-3-031-33465-8_60 SN - 2211-0852 VL - 45 SP - 782 EP - 792 PB - Springer Nature Switzerland AG CY - Switzerland AN - OPUS4-58726 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Mezhov, Alexander A1 - Zhang, K. A1 - Schmidt, Wolfram T1 - Interactions of Biobased Rheology Modifying Agents with Superplasticizer in Cement Paste JF - Construction Technologies and Architecture N2 - Organic admixtures are an indispensable component of modern concrete. Thus, their purposeful application is not only technically and economically viable but in addition an inevitable tool to make concrete more environmentally friendly. In this context, the use of polysaccharides has increasingly gained interest in the built environment as sustainable resource for performance enhancement. However, due to its origin, biopolymers possess a vast variety of molecular structures which can result in incompatibilities with other polymers present in concrete, such as superplasticizers. The present study highlights effects of the joint application of different types of starches and polycarboxylates with respect to their influence on cement hydration and structural build-up of cement pastes. KW - Polysaccharides KW - Superplasticizers KW - Hydration KW - Cement PY - 2022 DO - https://doi.org/10.4028/www.scientific.net/CTA.1.563 SN - 2674-1237 SP - 563 EP - 568 PB - Trans Tech Publications Ltd, Switzerland CY - Basel, Switzerland. AN - OPUS4-58325 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Priebe, Nsesheye Susan A1 - Schmidt, Wolfram A1 - Mota, Berta A1 - Leinitz, Sarah A1 - Kühne, Hans-Carsten A1 - Rogge, Andreas T1 - The effect of superplasticizers on rheology and early hydration kinetics of rice husk ash-blended cementitious systems JF - Construction and Building Materials N2 - Superplasticizers (SPs) have been employed in concrete technology for decades to improve the workability of concrete in its fresh state. The addition of SPs in cement-based systems affects the early properties. Although the interaction of the cement particles with various SPs has been extensively researched, there still exists limited research on the interaction of SPs with supplementary cementitious materials such as rice husk ash (RHA). This paper investigates the rheological properties and early hydration kinetics of RHA-blended systems with three types of SPs, a polycarboxylate ether (PCE) and two lignosulphonates (LS-acc and LS-ret). In rheological properties, the addition of SP causes an initial improvement of workability as the yield stress is significantly reduced. The pastes with PCE and LS-acc show a slight increase of yield stress over time whereas pastes with LS-ret tend to lower the yield stress slightly over time, further improving the workability. Without SP, pastes with RHA show a lower yield stress but an increase in plastic viscosity as cement is further replaced with RHA. The addition of the LS SPs is observed to lower the plastic viscosity but remains constant with further replacement of cement with RHA. This indicates that LS SPs further adsorbs on RHA particles and hydration products produced causing dispersion of the particles within the system. In early hydration kinetics, pastes with PCE retard hydration and the degree of retardation is further increased with LS SPs. In the presence of RHA, the retardation of LS SP systems is significantly reduced. The pastes with PCE show more ettringite in the SEM micrographs, but is observed to be shorter needles. This indicates an initial good workability for PCE. However, C-S-H and CH were observed to be low in quantity, whereby the pastes with LS show more nucleation sites for C-S-H and CH. The ettringite needles in the LS systems were similar in quantity and more elongated in some cases but not abundant as in the PCE systems. KW - Plastic viscosity KW - Cement KW - CO2 reduction KW - Supplementary cementitious materials KW - Rice husk ash KW - Superplasticizers KW - Hydration KW - Rheology KW - Yield stress KW - Slump flow PY - 2017 UR - http://www.sciencedirect.com/science/article/pii/S0950061817310978?via%3Dihub DO - https://doi.org/10.1016/j.conbuildmat.2017.05.197 SN - 0950-0618 SN - 1879-0526 N1 - Geburtsname von Priebe, Nsesheye Susan: Msinjili, N. S. - Birth name of Priebe, Nsesheye Susan: Msinjili, N. S. VL - 150 SP - 511 EP - 519 PB - Elsevier Ltd. AN - OPUS4-41036 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Ramirez Caro, Alejandra A1 - Pauli, Jutta A1 - Mota, Berta A1 - Simon, Sebastian A1 - Schmidt, Wolfram A1 - Resch-Genger, Ute T1 - C⁠3A passivation with gypsum and hemihydrate monitored by optical spectroscopy JF - Cement and Concrete Research N2 - Tricalcium aluminate (C⁠3A) is found with less than 10% wt. of the total composition; however, during hydration, C⁠3A plays an important role in the early hydration of cement in the presence of gypsum as a set retarder. The aim of this investigation is to assess the suitability of optical spectroscopy and a dye-based optical probe to monitor early hydration of C⁠3A in the presence of gypsum and hemihydrate. Optical evaluation was performed using steady-state fluorescence and diffuses reflectance spectroscopy (UV-VisDR). Phase characterization during hydration was done with in-situ X-ray diffraction. UV-VisDR with a cyanine dye probe was used to monitor the formation of metastable phases and was employed together with fluorescence spectroscopy, to follow the Aggregation and disaggregation of the dye during hydration. In conclusion, for the first time, a cyanine dye was identified as a feasible and stable probe to monitor C⁠3A hydration changes in the presence of calcium sulfate. KW - Dye KW - Photoluminescence KW - Fluorescence KW - Reflection spectroscopy KW - Cement KW - Hydration KW - Method development PY - 2020 DO - https://doi.org/10.1016/j.cemconres.2020.106082 VL - 133 SP - 106082 PB - Elsevier Ltd. CY - Amsterdam AN - OPUS4-50952 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -