Modifications of dolomite-based self-compacting concrete properties using mineral additives

U radu su opisana istraživanja svojstava samozbijajućih (SCC) betona spravljenih s dolomitnim filerom i materijalima koji posjeduju pucolanska svojstva, letećim pepelom i metakaolinom, kao zamjena za cement u različitim postotcima. Projektirano je sedam mješavina sa jednakim omjerom voda/prah i jednakim udjelom praškastog materijala. Ispitivanja svježih svojstava su se sastojala od ispitivanja rasprostiranja slijeganjem, ispitivanja L-kutijom i ispitivanja segregacije, a u očvrsnulom stanju je ispitana tlačna čvrstoća i modul elastičnosti za različite starosti betona od 2, 7, 14, 28 i 365 dana. Kako bi se pratila aktivnost dodanih mineralnih dodataka u betonske mješavine, ispitana je i toplina hidratacije. Dobiveni rezultati pokazuju da dodatak letećeg pepela u mješavinama poboljšava svojstva obradljivosti, dok uporaba metakaolina poboljšava mehanička svojstva. Usporena pucolanska aktivnost letećeg pepela usporava razvoj tlačne čvrstoće, ali rezultati dobiveni ispitivanjem nakon godinu dana starosti pokazuju da konačna čvrstoća betona s dodatkom letećeg pepela nije manja u odnosu na referentnu mješavinu.This paper addresses fresh and hardening properties of self compacting concretes (SCC) made with dolomite filler and pozzolanic materials, fly ash and matekaolin as cement replacement in different amounts. For this study, seven mixtures were prepared with a constant water-to-powder ratio and powder content. Fresh SCC properties were assessed by means of slump flow, L-box and sieve segregation test, while hardened properties were evaluated by means of compressive strength and modulus of elasticity at ages of 2, 7, 14, 28 and 365 days. In addition, the activity of mineral additives was assessed by heat of hydration measurement. Obtained results showed that mixtures containing fly ash exhibited better performance concerning workability properties needed for SCC, while cement replacement with metakaolin enhanced the mechanical properties. Slower pozzolanic activity of fly ash reflected in slower strength development, but ultimate strength obtained at the age of 365 days was not reduced by the presence of fly ash