The aim of this work was to observe the impact of the milling technique employed by the DESI 11 disintegrator on the properties of fly ash. This type of mill is a high-speed pin mill with two counter rotors. The device selected for study allows the use of rotors with different working tools. In this case, two types of rotors were selected, identified as BR-AR and OR rotors. The OR rotor has cylindrical teeth, while the teeth on the AR-BR rotor can be described as rhomboidal. The fly ash was ground by 1, 2, 3, 5, and 10 passes through the mill. The Blaine specific surface area, particle size and particle size distribution were measured for each sample. The pozzolanic activity was also determined via a modified Chapelle test, and its influence on the shape of the grains was assessed by SEM. The results were compared together and with the original fly ash. There was a steep increase in the specific surface area and pozzolanic activity after the first pass through the mill. The second pass of ash through the mill did not increase the specific surface area due to strong aggregation, which gradually changes into agglomeration. However, the pozzolanic activity still increased during the aggregation phase. This phenomenon was clearly observable for both types of selected rotors. Based on the results, we can say that in the case of fly ash, a high-speed disintegrator can be a promising means of improving its properties via grinding and mechanical activation. Keywords: high speed grinding, fly ash, pozzolanic activity Namen dela je opazovati posledice uporabljene tehnike mletja, v DESI 11 mlinu, na lastnosti lete~ega pepela. To je mlin z veliko hitrostjo, z dvema nasprotnima rotorjema. Naprava, izbrana za {tudij, omogo~a uporabo rotorjev z razli~nimi orodji. V tem primeru sta bila izbrana dva razli~na rotorja, ozna~ena kot AR-BR in OR rotor. OR rotor ima cilindri~en zob, medtem ko je zob na AR-BR rotorju ozna~en kot romboidalen. Lete~i pepel je bil zmlet z 1, 2, 3, 5 in 10 prehodi skozi mlin. Za vsak vzorec so bile izmerjene Blainova specifi~na velikost povr{ine ter velikost in razporeditev delcev. Pucolanska aktivnost je bila dolo~ena z modificiranim Chapelle testom. Vpliv na obliko zrn je bil dolo~en s SEM. Rezultati so bili primerjani z originalnim lete~im pepelom. Po prvem prehodu skozi mlin se je skokovito pove~ala specifi~na povr{ina in pucolanska aktivnost. Drugi prehod pepela skozi mlin ni pove~al specifi~ne povr{ine zaradi mo~ne agregacije, ki se je postopoma spremenila v aglomeracijo. Vseeno pa je pucolanska aktivnost {e nara{~ala med fazo agregacije. Ta pojav je bil jasno opa`en pri obeh vrstah rotorjev. Na osnovi teh rezultatov lahko re~emo, da je v primeru lete~ega pepela dezintegrator z veliko hitrostjo obetajo~e sredstvo, da z mletjem in mehansko aktivacijo izbolj{amo njegove lastnosti. Klju~ne besede: mletje z veliko hitrostjo, lete~i pepel, pucolanska aktivnost

The purpose of research work has been to verify an influence of α-gypsum grinding on its final property. The production of α-gypsum was performed by pressureless method in salt solution with partial substitute still used dehydrating solution of sodium chloride and calcium chloride.

By volume, there is no other material used as much as concrete. Its mechanical properties, durability and favorable price makes concrete the perfect construction material. In last few decades, we are seeing a growing trend of partial Portland cement’s replacement with secondary raw materials, most commonly with fly ash. So-called high volume fly ash (HVFA) concretes usually contains over 50% of it. While HVFA concrete’s long-term properties and price are improved over the classical one, its early age properties are often affected negatively. Here, a highly reactive pozzolans enters the scene. Materials like microsilica and metakaolin are known to accelerate concrete’s strength development and improve early age characteristics. In this paper, nanosilica is used for this purpose. These SiO2 nanoparticles possesses a much higher surface area and thus reactivity. Three mixtures with 0, 40 a 60% portland cement’s replacement with fly ash were prepared and tested with and without addition of small amount of nanosilica. Effects on compressive strength, static and dynamic moduli of elasticity and resistivity against water pressure were observed. Results clearly demonstrates that even with dosage in the range of tenths of percent, nanosilica can significantly improve concrete’s properties.

At present the demand for thermal insulation materials is bigger than ever before. Also cement foam or foamconcrete, the mixture of cement mortar and technical foam can be one of such materials. Due to its liquid consistency this material can be simply applied in fresh status on uneven board surfaces where application of common thermal insulating materials would be very complex and time consuming.This work is involved in use of fly ash in foamconcrete and polystyrene-concrete compositions; these are very lightweight concretes produced from fine-grained cement mortars by its foaming using foamable admixtures. The objective of this work is to verify whether final physical and mechanical properties are improved when fly ash is applied within the mixture, in particular, the compressive strength thermal coefficient and stability after 12 hours from mixing.

Within the task the so called high-temperature X-ray diffraction analysis (HT-XRD) was used in the field of sulphated binders. Gypsum or calcium sulphate CaSO4.2H2O is the basic raw material for the sulphated binder production. As it is known by gradual warming of gypsum its different phase transformations can be obtained which significantly differ in its properties. Using this analysis identifications of temperatures of particular phase transformations in the CaSO4·xH2O system can be performed.