Ein mineralisches Bindemittel auf Basis Olivin

Research output: ThesisMaster's Thesis

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Abstract

Due to the ongoing climate problem the carbon footprint of processes and products has become the focus of attention in recent years. The production of cement and cement products, which are essential for the modern construction industry, is associated with considerable energy consumption and CO2 emissions. To find alternatives to conventional production methods and products, the suitability of olivine and oxalic acid dihydrate as raw materials for acid-base cements is being investigated. The olivine used was crushed, ground and the fineness of the milled product was verified using a Blaine device and laser granulometric analysis. The density of the olivine was determined using a gas pycnometer. The chemism and mineral composition of the raw material was determined by X-ray diffractometry and energy-dispersive X-ray spectroscopy and the microstructure was examined under a reflected light microscope and scanning electron microscope. In the further course, mixtures of olivine, oxalic acid and deionized water were prepared, which were shaped into 20x20x20 mm cubes in a foiled steel mould. Different mixtures were obtained by changing the parameters (specific surface area, mass ratio of olivine to oxalic acid and W/C ratio). The influence of the mixing sequence of the components and the influence of the storage conditions on the results were analysed. The end of solidification of the individual mixtures was determined using a Vicat needle test and the cubes were examined regarding their compressive strength and changes in volume and length during drying and storage. In addition to the tests with olivine, wollastonite (CaSiO3) and slag were tested as raw materials, a mortar mixture of olivine and quartz sand was produced and a comparative test on water resistance with CEM II was carried out. In the course of this work, moulds made of different materials were also tested, as a steel mould (uncoated) is not suitable for this type of binder. The experimental design based on the Box-Behnken design was carried out using MATLAB and the results of the test series were presented graphically. A correlation matrix was created in Microsoft Excel for further analysis of the results. The following conclusions were drawn: Especially at a low olivine to oxalic acid ratio, an high increase in volume / length of the cubes can be observed during solidification. The compressive strength is influenced by the competing effects of the occuring porosity and the amount of magnesium oxalate formed. The compressive strength increases with increasing specific surface area of the basic component (olivine), as the extent of the reaction and the amount of binder phase are increased. The solidification time is influenced in particular by the specific surface area and the W/C ratio. The influence of the W/C ratio on the compressive strength and solidification time depends on the other parameters and there is no linear dependency. The highest compressive strength values can be achieved with a high specific surface area, a medium Ol/Ox ratio and a low W/C ratio.

Details

Translated title of the contributionA mineral binder based on olivine
Original languageGerman
QualificationDipl.-Ing.
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Award date22 Mar 2024
Publication statusPublished - 2024