Pycnomatic atc

For BA and metakaolin, specific density and Blaine specific surface were measured. The specific density was tested using a Pycnomatic ATC (Thermo Scientific, Milan, Italy). Blaine specific surface was assessed by a Blaine device [41 ].
For the determination of pozzolanic activity of BA and metakaolin, Chapelle test was used [42 ].
Chemical composition of BA and Mefisto K05 was measured by X-ray fluorescence (XRF) using Axios sequential WD-XRF spectrometer (PANalytical, Almelo, The Netherlands).
Morphology of binder constituents was studied by scanning electron microscope (TESCAN Lyra 3, Tescan Brno, s.r.o., Brno, Czech Republic) equipped with a FEG electron source. Energy dispersive spectroscopy (EDS) was performed with the analyzer X-MaxN, SDD detector (Oxford instruments, High Wycombe, UK) and AZtecEnergy software (Oxford instruments) to determine the chemical composition.
X-ray diffraction (XRD) was performed on Bruker D8 Discoverer (Bruker AXS GmbH, Karlsruhe, Germany) powder diffractometer with parafocusing Bragg–Brentano geometry at room temperature using CuK_α radiation [34 (link)].
The particle size distribution was tested using an apparatus Analysette 22 Micro Tec plus (Fritsch, Idar-Oberstain, Germany) working on a laser diffraction. The device allows identification of particles having size from 0.08 μm to 2 mm.

The bulk density, matrix density, and total open porosity were investigated as the basic physical characteristics. Bulk density was measured on the gravimetric principle, using the sample size measured by a digital length meter and its dry mass. For this measurement, 10 cubic samples of side 100 mm were used. The matrix density was determined by helium pycnometry using Pycnomatic ATC (Thermo). At the application of Pycnomatic ATC, a well dried sample of studied material is weighed and placed in a calibrated reference chamber of known volume. Helium is first loaded at known pressure in a calibrated reference chamber and then expanded into the sample chamber. Once the pressure is stabilized, experimental data are collected and the material volume is accessed. The accuracy of the gas volume measurement using this device is ±0.01% from the measured value, whereas the accuracy of used analytical balances is ±0.0001 g. On the basis of bulk density and matrix density measurements, the total open porosity was calculated in a common way [16 ]. The relative expanded uncertainty of the applied testing method was 5%.

The actual density of the applied precursors and the density of the manufactured geopolymer were determined. The actual density was determined with a Pycnomatic ATC (Thermo Fisher Scientific, Massachusetts, USA) with the PN-EN ISO 18753: 2006 standard (“High-quality ceramics (advanced ceramics, technical advanced ceramics)—Determination of the actual density of ceramic powders using the pycnometric method”). Pycnometers use a gas displacement technique to determine the actual density. Helium was used as the gas because helium atoms have very small diameters and can penetrate even extremely small pores in solids. As the outer surface of the samples did not show significant roughness, the density of the samples was determined using the geometric method for solid materials. The density was determined as the mean of the measurements for the four samples. The samples were measured with a laboratory caliper with a measurement accuracy of 0.01 mm, and the mass of the samples was determined with a laboratory precision analytical balance RADWAG PS 200/2000.R2 (maximum load: 200/2000 g; reading accuracy: 0.001/0.01 g).