Changes in the composite structure and parameters after an exposure to a synergic action of various extreme conditions

Abstract

The research presented in this paper is aimed at studying the properties of composites designed for a redevelopment of reinforced concrete structures where it is possible to expect an increased risk of fire, i.e., shock actions of extreme temperatures. Such conditions may occur, for example, in transport constructions, particularly in tunnels. We have developed two recipes (formulas) for materials based on a polymer-cement matrix and a porous filler. These materials were subjected to cyclic freezing and de-freezing in combination with a water action. In terms of a long-term durability, we monitored the characteristics after 50 and 100 cycles. The impact of an increased humidity was not considered in this phase of the research. After testing the frost resistance, the bodies were dried up. Then, temperature shocks of (400, 600 and 1000)°C followed. The bodies were cooled down under control, with gradual temperature decreases. The reason for assessing the impact of these two exposure conditions on the properties of designed materials was mainly the use of the porous filler. This filler has a favourable effect on the temperature resistance. On the other hand, however, the frost resistance can be negatively affected in combination with water. Studying the influence of the above two exposures was carried out using the basic physico-mechanical and also physico-chemical methods. We also utilized analytical methods for assessing the microstructure. The structure was also examined using an innovative imaging technique allowing a three-dimensional visual assessment, which was primarily aimed at identifying faults of the structure. Keywords: composite, polymer-cement matrix, cementitious supplementary material, high temperature, frost resistance, synergic, microstructure Namen predstavljene raziskave je {tudij lastnosti kompozitov namenjenih obnovi betonskih zgradb, kjer je mo`no pri~akovati pove~ano nevarnost po`ara in delovanje ekstremnih temperatur. Taki pogoji se lahko pojavijo, na primer, v prometnih konstrukcijah, posebno v tunelih. Razvili smo dva recepta (formuli) materialov, ki temeljijo na me{anici polimer-cement in poroznega polnila. Ti materiali so bili izpostavljeni cikli~nemu zamrzovanju in odtajanju, v kombinaciji z delovanjem vode. V smislu dolge zdr`ljivosti, smo pregledali zna~ilnosti po 50 in 100 ciklih. Vpliv pove~anja vla`nosti v tem delu raziskav ni bil obravnavan. Po preizku{anju odpornosti na mraz, so bila telesa osu{ena. Sledili so temperaturni {oki na (400, 600 in 1000)°C. Telesa so bila kontrolirano ohlajena, s postopnim zmanj{anjem temperature. Razlog za ocenjevanje u~inka teh dveh pogojev izpostavitve na lastnosti materiala, je bila predvsem uporaba poroznega polnila. To polnilo ima ugoden vpliv na temperaturno obstojnost. Po drugi strani pa je lahko odpornost na zmrzal manj{a v kombinaciji z vodo. [tudij vpliva obeh na~inov izpostavitve je bil izveden z uporabo osnovnih fizikalno-mehanskih in tudi fizikalno-kemijskih metod. Za ocenjevanje mikrostrukture smo uporabili tudi analiti~ne metode. Str...

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