This paper presents the results of an experimental study aimed at determining the influence of wood fly ash (WFA) from three Croatian power plants on the properties of concrete. First, the chemical and physical properties of WFA’s were determined. It was found that these properties are highly influenced by combustion technology, the type and parts of wood used as fuel, and the local operating conditions. Subsequently, workability, heat of hydration, stiffness development, 28-day compressive strength, apparent porosity, and capillary absorption were determined on concrete mixes prepared with WFA as cement replacement from 5–45% by weight. Cement replacement up to 15% with the finest WFA accelerated hydration, stiffness development, and increased compressive strength of concrete up to 18%, while replacement with coarser WFA’s led to a decrease in compressive strength of up to 5% and had more gradual heat liberation. The dominant effect that could explain these findings is attributed to the filler and filling effect mechanisms. At the same time replacement content of up to 45% had very little effect on capillary absorption and could give concrete with sufficiently high compressive strength to be suitable for construction purposes.

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Preliminary notesThis 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.Keywords: dolomite filler; fly ash; fresh properties; hardened properties; metakaolin; mineral additives; self-compacting concrete Utjecaj mineralnih dodataka na promjenu svojstava samozbijajućeg betona s dolomitnim fileromPrethodno priopćenje 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. Ključne

This paper presents an experimental research on the performance of high-strength selfcompacting concrete (SCC) with different mineral additives after exposure to high temperature of up to 600°C. For this purpose, four SCC mixtures were studied: one reference and three mixtures where the Portland cement was replaced with mineral additive (fly ash, metakaolin and limestone) in certain proportions. After natural cooling in the furnace, compressive strength and static modulus of elasticity were determined and compared to results obtained from other studies and those provided in EN 1992-1-2 and EN 1994-1-2 for normal-vibrated concrete. Additionally, in order to characterize the damage of the specimens caused by high temperatures, AE parameters during compression test of heated and unheated specimens were also obtained.