Drėgnio įtaka akytojo betono savybėms

Abstract

Remiantis EN 771-4 reikalavimais ištirta drėgnio įtaka autoklavinio akytojo betono (AAC) savybėms. Nustatyta, kad AAC vandens įgerties greitis 400 kg/m3 tankio bandiniuose bandymo pradžioje (po 10 min) yra beveik 25 % didesnis negu 600 kg/m3 tankio betono, tačiau bandymo pabaigoje (po 90 min) pastebimas priešingas vaizdas: 600 kg/m3 tankio AAC bandinio įgerties greitis yra 7 % didesnis negu 400 kg/m3 tankio betono. Sąlyginė susitraukimo džiūstant vertė εcs kinta nuo 0,1 iki 0,23 mm/m priklausomai nuo AAC tankio. Mažiausia deformacija yra 600 kg/m3, didžiausia – 400 kg/m3 tankio betonų. Ištirta, kad 6 % drėgnio bandinių stipris gniuždant bei lenkiant yra apie 35 % mažesnis už sausų bandinių stiprį. Nustatyta, kad 400–450 kg/m3 tankio AAC įmirkytų vandenyje bandinių drėgnis (64–76 % kietųjų medžiagų masės) neturi įtakos bandinių atsparumui šalčiui, kuris priklauso tik nuo mišriosios rišamosios medžiagos kalkių ir cemento santykio.

The moisture content in porous concrete (AAC) can vary in a wide range. The maximum water sorption in AAC specimens can reach up to 76%, after the hydrothermal treatment in an autoclave the moisture content is about 35%, while AAC maintenance moisture content in partition walls varies from 4% to 6%. The AAC strength characteristics in Soviet times were determined according to GOST requirement by compressing or bending dry specimens. At present, when ES standards are in force in Lithuania, the compressive and flexural strength is determined for specimens containing 6 ±2% of moisture. The fluctuation of moisture content in AAC specimens has an influence on its strength characteristics and other properties. The aim of this work was to investigate the influence of 6 ±2% moisture content on some of the AAC (400-600) kg/m3 properties. Experiments to determine AAC specimen frost resistance were conducted with specimens saturated to different degrees and immersed in water for 48 h. It was determined during strength testing that in dry AAC specimens compressive and flexural strength is 30% to 35% higher than for the same density specimens containing 6 ±2% of moisture. The influence of water absorption on AAC frost resistance was investigated for specimens with a density of 450 kg/m' and absorbed water content 68% to 76%. The results showed that AAC frost resistance depended mainly on the amount of cement used in the formation mixture binder composition, while water absorption did not have any significant influence.