Effect of furnace slag on the hydration of Portland cement and the development of mechanical properties of the cement mortar : diploma thesis

Portland cement je jedan od najčešće korištenih mineralnih veziva u graditeljstvu. Budući da proizvodnja cementa zahtjeva veliku količinu energije sam proces je opterećen velikom emisijom stakleničkih plinova i to prvenstveno ugljikova dioksida koji ima značajan utjecaja na globalno zatopljenje. Upravo zbog navedenog, već dugi niz godina znanstvena zajednica istražuje primjenu različitih materijala kao zamjenskih dodataka cementu u proizvodnim procesima ili čak alternativa cementu. Svi pokušaji zapravo vode globalnom održivom razvoju i najnižem mogućem utjecaju na okoliš. Utjecaj troske visoke peći kao zamjenskog dodatka na kinetiku hidratacije kao i na vrijednosti razvijene tlačne i savojne čvrstoće u sustavima cementnih pasta i mortova određen je uz korištenje troske kao zamjenskog dodatka na masu cementa tipa CEM I 42,5R u masenim iznosima od 5, 15, 20, 25, 30 i 40 mas.%. Jedna serija mortova pripravljena je sa cementom tipa CEM II B-S 42,5N. Uzorci mortova njegovani su u vodi do trenutka provedbe mjerenja razvijenih tlačnih i savojnih čvrstoća koja su provedena nakon 3, 7, 14, 28, 70 i 90 dana hidratacije. Rezultati istraživanja ukazuju da nakon 90 dana hidratacije čak i sustav sa 40 mas.% zamjenskog dodatka troske postiže više vrijednosti razvijene tlačne čvrstoće u odnosu na referentni uzorak morta (mort bez zamjenskog dodatka troske). Mjerenja također potvrđuju da nema značajnih odstupanja u vrijednostima razvijenih mehaničkih svojstava cementa CEM II B-S 42,5N u odnosu na sustave mortova koji su pripravljeni naknadnim korištenjem troske kao zamjenskog dodatka u sustavima cemenata tipa CEM I 42,5R. Rezultati provedene kinetičke analize ukazuje na blago snižavanje vrijednosti konstante brzine procesa nukleacije i rasta, dok s druge strane bitno utječe na dužinu trajanja samog procesa pomičući ga prema kasnijim vremenima hidratacije. Pomak procesa nukleacije i rasta prema kasnijim vremenima ima za posljedicu veći stupanj hidratacije klinkera minerala cementa, što utječe i na mehanička svojstva sustava mortova, ali i na ranije pojavljivanje perioda u kojem u je difuzija ograničavajući proces hidratacije kao posljedica povećanja gustoće hidratacijskih produkata u ranijem periodu hidratacije.Portland cement is one of the most commonly used mineral binders in the Civil Engineering. Since the Portland cement production requires a large amount of energy, the process itself is burdened with a high greenhouse gas emission, primarily carbon dioxide, which has a significant impact on global warming. For a very long time, the scientific community has been investigating the application of different materials as substitute cement additives in production processes or even alternative to the cement as new mineral binder. All attempts actually lead to global sustainable development and the lowest possible impact of cement industry on the environment. The effect of the furnace slag from iron production industry as a substitute additive on the hydration kinetics in the system of paste as well as the values of developed compressive and flexural strength in the system of the cement mortar was determined by using the slag as a substitute additive on CEM I 42.5R where the cement mass has been replaced with slag in the amounts of 5, 15, 20, 25, 30 and 40 mass % by weight. One mortar serie was made with the cement type CEM II B-S 42.5N prepared in the laboratory. Samples of the cements mortar were kept in the thermostated water until the measurements of developed compressive and flexural strengths were performed after 3, 7, 14, 28, 70 and 90 days of hydration. The results show that after 90 days of hydration, even the system with 40 mass % of slag shows higher value of developed compressive strength relative to the reference mortar (mortar without replacement slag). The measurements also confirm that there are no significant deviations in the values of the developed mechanical properties of cement CEM II B-S 42.5N compared to the mortar systems were slag was used as a substitute additive in CEM I 42.5R cements systems. The results of the kinetic analysis showed a slight decrease in the value of the nucleation and growth rate constant, while on the other hand, it significantly influenced the duration of the process itself by moving it towards higher hydration times. The shift of nucleation and growth to later times results in a higher degree of hydration of the cement clinker minerals, which influences the mechanical properties observed in the mortar systems, but also the earlier appearance of the period in which the diffusion is a limiting hydration process as a consequence of increasing of the microstructural density of the hydration products in earlier hydration period