Marija Jelčić Rukavina

Shrinkage Behaviour of Fibre Reinforced Concrete with Recycled Tyre Polymer Fibres

Different types of fibres are often used in concrete to prevent microcracking due to shrinkage, and polypropylene fibres are among the most often used ones. If not prevented, microcracks can lead to the development of larger cracks as drying shrinkage occurs, enabling penetration of aggressive substances from the environment and reducing durability of concrete structures. The hypothesis of the present research is that polypropylene fibres, used in concrete for controlling formation of microcracks due to shrinkage, can be replaced with recycled polymer fibres obtained from end-of-life tyres. To test the hypothesis, concrete mixtures containing polypropylene fibres and recycled tyre polymer fibres were prepared and tested. Experimental programme focused on autogenous, free, and restrained shrinkage. It was shown that PP fibres can be substituted with higher amount of recycled tyre polymer fibres obtaining concrete with similar shrinkage behaviour. The results indicate promising possibilities of using recycled tyre polymer fibres in concrete products. At the same time, such applications would contribute to solving the problem of waste tyre disposal.

Mechanical Properties of Self-Compacting Concrete with Different Mineral Aditives After High Temperature Exposure

This paper presents an experimental research on the performance of high-strength selfcompacting concrete (SCC) with different mineral additives after exposure to high temperatures 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, acoustic emission (AE) parameters during compression test of heated and unheated specimens were also obtained which showed good non-destructive tool for identifying exposure temperature of the concrete needed for the assessment of concrete structures after fire.

Comparative full-scale fire performance testing of ETICS systems

U ovom radu prikazano je ispitivanje fasadnih sustava u stvarnoj veličini. Ispitivanje je provedeno s ciljem usporedbe ponašanja ETICS sustava s različitim toplinsko izolacijskim slojem (goriva izolacija, goriva izolacija s protupožarnom barijerom od negorivog materijala, negoriva izolacija) u uvjetima požara. Uzorci su izrađeni i ispitani u skladu s normom BS 8414-1:2002, a provedena su i dodatna mjerenja kako bi se dobili bitni podaci koji omogućuju bolje razumijevanje ponašanja ETICS sustava u požaru.A full-scale test has been performed to determine fire performance of different ETICS systems (combustible insulation, combustible insulation with fire barrier, noncombustible insulation). Test specimens were constructed and tested according to BS 8414-1:2002, while additional measurements were also conducted to obtain valuable information for better understanding of fire performance of systems used. U ovom radu prikazano je ispitivanje fasadnih sustava u stvarnoj velicini. Ispitivanje je provedeno s ciljem usporedbe ponasanja ETICS sustava s razlicitim toplinsko izolacijskim slojem (goriva izolacija, goriva izolacija s protupožarnom barijerom od negorivog materijala, negoriva izolacija) u uvjetima požara. Uzorci su izrađeni i ispitani u skladu s normom BS 8414-1:2002, a provedena su i dodatna mjerenja kako bi se dobili bitni podaci koji omogucuju bolje razumijevanje ponasanja ETICS sustava u požaru.

Ocjena stanja betonskog obalnog zida izloženog djelovanju morske vode više od 30 godina

U radu su prikazane posljedice dugotrajnog izlaganja betonskih konstrukcija morskom okolisu, na primjeru betonskih blokova obalnog zida koji se nalaze u moru vise od 30 godina. Na blokovima je provedeno ispitivanje mehanickih (tlacna cvrstoca) i trajnosnih (plinopropusnost i kapilarno upijanje) svojstava, svojstava homogenosti (odskok sklerometrom i brzina prolaska ultrazvuka) te kemijska analiza (kolicina kloridnih i sulfatnih iona). Osim ispitivanja, provedeno je modeliranje ponasanja betona u morskoj vodi uz pomoc programskih paketa Stadium i Conclife.

Usporedba ponašanja različitih ETICS sustava u uvjetima požara ispitivanjem u stvarnoj veličini

U ovom radu prikazano je ispitivanje fasadnih sustava u stvarnoj veličini. Ispitivanje je provedeno s ciljem usporedbe ponašanja ETICS sustava s različitim toplinsko izolacijskim slojem (goriva izolacija, goriva izolacija s protupožarnom barijerom od negorivog materijala, negoriva izolacija) u uvjetima požara. Uzorci su izrađeni i ispitani u skladu s normom BS 8414-1:2002, a provedena su i dodatna mjerenja kako bi se dobili bitni podaci koji omogućuju bolje razumijevanje ponašanja ETICS sustava u požaru.A full-scale test has been performed to determine fire performance of different ETICS systems (combustible insulation, combustible insulation with fire barrier, noncombustible insulation). Test specimens were constructed and tested according to BS 8414-1:2002, while additional measurements were also conducted to obtain valuable information for better understanding of fire performance of systems used. U ovom radu prikazano je ispitivanje fasadnih sustava u stvarnoj velicini. Ispitivanje je provedeno s ciljem usporedbe ponasanja ETICS sustava s razlicitim toplinsko izolacijskim slojem (goriva izolacija, goriva izolacija s protupožarnom barijerom od negorivog materijala, negoriva izolacija) u uvjetima požara. Uzorci su izrađeni i ispitani u skladu s normom BS 8414-1:2002, a provedena su i dodatna mjerenja kako bi se dobili bitni podaci koji omogucuju bolje razumijevanje ponasanja ETICS sustava u požaru.

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

This paper addresses fresh and hardening properties of self compacting concretes (SCC) made with dolomite filer 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.

Condition assessment of concrete pier after three decades of exposure to sea water

U radu su prikazane posljedice dugotrajnog izlaganja betonskih konstrukcija morskom okolisu, na primjeru betonskih blokova obalnog zida koji se nalaze u moru vise od 30 godina. Na blokovima je provedeno ispitivanje mehanickih (tlacna cvrstoca) i trajnosnih (plinopropusnost i kapilarno upijanje) svojstava, svojstava homogenosti (odskok sklerometrom i brzina prolaska ultrazvuka) te kemijska analiza (kolicina kloridnih i sulfatnih iona). Osim ispitivanja, provedeno je modeliranje ponasanja betona u morskoj vodi uz pomoc programskih paketa Stadium i Conclife.