Ispitivanje uticaja temperature sinterovanja na termostabilnost niskocementnih visokoaluminatnih vatrostalnih betona

Abstract

Disertacija je imala cilj da prati ponašanje niskocementnog betona na bazi glinice pri termošoku i kavitaciji. Prvi deo eksperimenata obuhvatio je sintezu betona jednog sastava uz jednake uslove nege svih pripremljenih uzoraka. Nakon toga, uzorci su sinterovani na tri različite temperature, 1100 °C, 1300 °C i 1600 °C u trajanju od tri sata, da bi se pratio uticaj temperature sinterovanja na svojstva betona i nastalu strukturu. Posebna pažnja bila je usmerena na analizu uticaja temperature sinterovanja betona na ponašanje pri ispitivanju termostabilnosti i otpornosti na kavitaciju. Otpornost vatrostalnog betona na nagle promene temperature određena je primenom standardizovane metode kaljenjem uzoraka u vodi. Pri ispitivanju termostabilnosti vatrostalnih materijala praćene su promene uobičajenih parametara, kao što su mehanička i fizička svojstva. Analiza ovih svojstava podrazumevala je primenu destruktivnih metoda. Pored toga, primenjene su i nedestruktivne metode dok su rezultati ovih ispitivanja korišćeni za praćenje ponašanja betona pri termošoku i analizi uticaja temperature sinterovanja na ponašanje uzoraka pri termošoku. Jedna od korišćenih nedestruktivnih metoda bila je analiza slike kojom je praćen stepen oštećenja površine i unutrašnjosti uzoraka sa brojem ciklusa termošoka. Takođe je primenjena metoda ultrazvučnih merenja koja je omogućila praćenje prostiranja brzine ultrazvuka i promena elastičnih osobina sa brojem ciklusa termošoka. Promene pritisne i savojne čvrstoće praćene su klasičnom destruktivnom metodom prema standardizovanoj proceduri. Pored toga, na osnovu promena brzine prostiranja ultrazvuka, stepena oštećenja unutrašnjosti i površine, urađeni su modeli kojima bi bilo moguće predvideti promene pritisne čvrstoće sa brojem ciklusa termošoka. Na osnovu rezultata izračunatih i stvarnih vrednosti promena čvrstoće urađena je validacija dobijenih modela. Takođe je definisan kritičan broj ciklusa termošoka do pucanja sve tri serije uzoraka. Razvijeni su i parametri otpornosti na lom i oštećenja (R parametri) bazirani na termomehaničkim svojstvima vatrostalnog betona kojima je moguće predvideti i definisati ponašanje betona u uslovima naglih promena temperature...

The aim of this thesis was to monitor behavior of alumina based low cement castable during the thermal shock and the cavitation. The first part of experiments included synthesis of one castable composition with the same cure conditions for all prepared samples. Then, the samples were sintered at three different temperatures (1100 °C, 1300 °C, and 1600 °C) with dwell time of 3 hours. The goal was to study influence of sintering temperature on castable properties and structure. Particular attention was focused on the influence of sintering temperature on the castable behavior during the investigation of thermal stability testing and cavitation resistance. Resistance of refractory castable to sudden temperature changes was determined by using standardized method of tempering samples to the water. Changes of common parameters such as mechanical and physical properties were monitored during the examination of castable thermal stability. The analysis of these properties included application of destructive methods. Besides, non‐destructive methods were used, too. The results of these tests served for monitoring the castable behavior during the thermal shock and analyzing the influence of sintering temperature. One of applied non‐destructive methods was the image analysis used for determining the damage level on the surface and inside the bulk of the sample depending on the number of thermal shock cycles. Also, the method of ultrasound measurements that allowed the monitoring of the ultrasound speed propagation and elastic properties change during the thermal shock was applied. Changes in compressive and flexural strength were measured by classic destructive method according to the standardized procedure. In addition, models for predicting compressive strength degradation during the thermal shock were made based on the changes in ultrasound velocity and the damage level at the surface and inside the bulk of the samples. Agreement between calculated and experimental strength values proved the validity of the proposed model. Critical numbers of thermal shock cycles until the sample crack for all series of samples were determined. Damage and crack resistance parameters (R parameters) were developed based on the thermomechanical properties of refractory castables. Also, these parameters can be used to predict and define castable behavior in conditions of sudden temperature changes...