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    Item type:Publication, Access status: without files ,
    Inert material with binding rim by reactive milling
    (2019)
    Schmidt-Döhl, Frank Michael
    ;
    Glück, Gabriel
    ;
    Schulenberg, David
    The use of hydraulic binders with an inert core and reactive shell may be an opportunity to develop more efficient mineral building materials. Reactive milling is one method to obtain such structures, known as a method of mechanochemistry. Tests were performed using CaO and CaCO3 as calcium containing components and cristobalite, silica fume and quartz as silicon containing components as powders using a planetary ball mill. The reaction products were examined using Attenuated Total Reflection (ATR) IR spectroscopy and light microscopy. A very clear new formation of a group of peaks around 900 cm-1 (typical for a calciumsilicate) was observed for CaO and cristobalite. The CaO/silica fume and CaO/quartz pairs behave similarly in principle. The tests showed that it seems possible to produce a material with an inert core, for example quartz, and a reactive rim, for example calciumsilicate, using reactive milling.
    Publicationtype: Conference Paper
      285
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    Item type:Publication, Access status: without files ,
    Pozzolanic activity of flint powder
    (2019)
    Osterhus, Lennart
    ;
    Ditz, Florian
    ;
    Schmidt-Döhl, Frank Michael
    It was tested whether powdered flint is able to reach pozzolanic properties comparable to fly ash. The flint aggregates were crushed and milled to three different grain size fractions comparable to coal fly ash. The powdered flint was characterized and subsequently used as a substitute in mortar prisms. The compressive strength tests showed a potentially pozzolanic reactive behavior at 28 days of two different fine grained flint fractions. But comparable investigations after 92 days showed that the typical subsequent hardening of pozzolanic materials could not be obtained. The strength was much lower than the strength of comparable specimens with fly ash. Further, thermogravimetric analysis of the tested mortars after 28 days showed a much lower portlandite consumption compared with mortar with fly ash. The study concludes that at least the examined powdered flint with high density does not have the opportunity to replace coal fly ash as pozzolan.
    Publicationtype: Conference Paper
      318