Selfhealing of concrete with dolomite aggregate through alkali carbonate reaction

Namen magistrske naloge je bil raziskati vpliv alkalno karbonatne reakcije na proces samoobnove (»selfhealing«) materialov s cementnim mineralnim vezivom. Vzorci so bili narejeni iz portlandskega cementa in dolomitnega agregata frakcije 0/4 mm ter dolomitne moke. Preizkušanci so bili v obdobju enega leta izpostavljeni dvema pospešenima pogojema staranja, deonizirani vodi in 1 molarni raztopini natrijevega hidroksida pri povišani temperaturi (60 °C). Med staranjem preizkušancev smo v različnih časovnih obdobjih opravljali preiskave z elektronskim mikroskopom, s pomočjo katerega smo spremljali samoobnovo vzorcev. Poleg tega so vzporedno potekale mehanske preiskave vzorcev za preverjanje vpliva efekta samoobnove preizkušancev. Ugotovili smo, da alkalno karbonatna reakcija vpliva na mehanske lastnosti staranih preizkušancev. Preiskave staranih preizkušancev so pokazale, da se v predhodno oblikovanih razpokah precipitirajo sekundarni kalcit in faze, ki vključujejo tako imenovane »nove faze«, ki so bogate z Mg, Al in Si. V časovnem obdobju enega leta je razvidno, da so se manjše razpoke popolnoma zapolnile. Pri večjih razpokah pa se je njihova širina učinkovito zmanjšala.The main goal of the master’s thesis was to investigate the influence of alkaline carbonate reaction on the process of self-repairing materials with a cement binder. The used mixture was composed of portland cement and dolomite in the role of aggregate and stone filler. Samples were exposed to accelerated testing conditions simulated by 1M NaOH at 60 °C or deionized water at 60 °C. During the ageing process, microstructure characteristics of the samples after various ageing periodes were investigated by means of electron microscopy. In addition, mechanical examinations of the samples were conducted to verify the effect of self-repairing in samples. It was shown that the alkaline carbonate reaction effects the mechanical properties of the aged samples. Namely, secondary calcite and phases that include so-called »new phases« enriched with Mg, Al and Si are precipitated within pre-existing cracks. Over a period of one year, we observed that small cracks were completely filled. In the case of larger cracks, the width was effectively reduced