Fire Resistance of Crushed Brick-Based Alkali-Activated Mortars

This study investigates the fire resistance of alkali-activated mortar incorporating crushed brick as both a precursor and aggregate. The optimal alkaline activator was identified as a combination of KOH and Na₂SiO₃, with a curing period of 3 days at 70 °C. Two mortar series were produced, each exhibiting different workability: on series comprised cement mortar, while the other included three alkali-activated mortars, with variations in the molarity of the KOH solution. The mortar samples were subsequently heated to 600°C, and their mechanical properties and mass were measured to determine residual values/losses. The best-performing alkali-activated and cement mortars underwent visual assessments of cross-sections to evaluate the impact of mortar consistency on fire resistance. Additionally, changes in mineralogy and microstructure were followed by instrumental techniques to clarify the results before and after heating. While cement mortars had superior mechanical properties at room temperature, alkali-activated mortars retained a higher percentage of their mechanical properties post-heating, demonstrating better fire resistance. Mortars with plastic consistency showed better fire resistance than those with fluid consistency. These findings suggest that brick-based alkali-activated mortars could be developed into fire protection boards for structural member

Poboljšanje izolacije od vazdušnog zvuka masivnog zida od giter bloka dodavanjem lakih sistema sa gips-kartonskim pločama

U Laboratoriji za akustiku i vibracije Instituta IMS u laboratorijskim uslovima sprovedena su ispitivanja na masivnom zidu od giter bloka i istog zida dodavanjem lakih obloga od mineralne vune i gips-kartonskih ploča sa jedne i sa obe strane masivnog zida. Ispitivanja su sprovedena u serijama prilikom instalacije svake od obloga kako bi se pratile merodavne vrednosti izolacionih moći u različitim fazama instalacije, a sve u cilju da se vidi koliko je poboljšanje zvučne izolacije dodavanjem lakih obloga na masivni zid

Recycling possibilities of wood-plastic composites (WPC)

Nowadays, the main goal is to minimize the negative impact of a product or service on the environment. Wood-plastic composites (WPC) can be produced in a sustainable way, with minimal waste. WPC composites can be produced from natural raw materials. They can also be produced as a result of recycling, where either wood or plastic come from the recyclate. In WPC production a large percentage of waste can be reused. WPC does not contain formaldehyde or aggressive organic compounds, it is usable product (it can be grinded and reused), as waste it is not hazardous and can be disposed of with other waste

The influence of crumb rubber on the freeze-thaw resistance of concrete

Waste tires are a persistent challenge in waste management. To reduce environmental impact and utilize this material more effectively, its use in concrete mixtures has been studied. This research aims to incorporate waste materials into concrete production while ensuring acceptable performance. The study presents results where fine aggregate was partially replaced with crumb rubber (2.5% and 5% by volume). All mixtures were designed with a w/c= 0.55 and compared with a control and a mixture with a chemical air-entraining admixture. Fresh concrete properties were monitored after 10, 30, and 60 minutes. After 60 minutes, rubber-modified mixtures showed increased air content and decreased density. The hardened concrete with rubber had lower compressive strength but better resistance after 200 freeze-thaw cycles compared to the control

Estimating the concrete compressive strength using ultrasound tomography

Evaluating the compressive strength of concrete without altering the structure is often achieved using non-destructive testing (NDT) methods. These techniques are popular in practice due to their low cost and the fact that they leave the structural elements intact. Among them, the rebound hammer and ultrasonic pulse velocity tests are the most frequently applied. However, a major drawback is their limited precision when compared to destructive methods. To overcome this issue, various analytical models have been introduced to better link NDT measurements with actual compressive strength values. In this investigation, a combined approach using both destructive and non-destructive techniques was adopted to assess in-situ concrete quality. Due to structural limitations, core extraction was only feasible from fourteen columns. A polynomial regression model was applied to establish a relationship between the compressive strength and the velocity of shear waves obtained from ultrasonic tomography

Primena površinski aktivne supstance ARKOPALA N 100 u ciglarstvu

U radu je ispitivana mogućnost primene ARKOPALA N 100 u ciglarskoj industriji. Pomenuta supstanca je dodata u vodu sa kojom se vlažila prethodno osušena i prerađena sirovina. Formirana su četri kompozita. Koncetracija ARKOPALA N 100 je varirala od 0 do 0,07%. Proces sušenja praćen je na uzorcima pločica. Snimljen je set izotermskih eksprimenata za svaki kompozit. Konstrujisane su zavisnosti efektivnog koeficijenta difuzije u funkciji od sadržaja vlage (Deff-MR). Oblikovani uzorci kockica su sušeni na 250C pri relativnoj vlažnosti od 75% dok apsolutni sadžaj vlage u njima nije spušten do 15, 10 i 5 %. Formirane su zavisnosti promene prtisne čvrstoće oblikovanih uzoraka u funkciji sadržaja vlage. Dobijene krive omogućile su nam da objektivno pratimo generisanje pukotina tokom sušenja i utvrdimo optimalu koncetraciju ARKOPALA N 100 koja omogućava da se iste izbegn

Beton modifikovan grafen-oksidom

S obzirom na to da je beton trenutno najrasprostranjeniji građevinski materijal, njegova čvrstoća i izdržljivost su njegove bitne karakteristike. Nedavna dostignuća u vidu primene vlakna nanodimenyije, kao što su ugljenične nanotube i grafen oksid, poboljšala su performanse betona. Grafen oksid (GO) je dvodimenzionalni planarni list komprimovanih atoma ugljenika u konfiguraciji saća debljine 0,335 nm. GO je obećavajući nanomaterijal zbog svojih jedinstvenih svojstava, naime, dobio je međunarodnu pažnju zbog svojih izvanrednih mehaničkih, optičkih i termičkih svojstava. Pored regulacije sekundarnog mehanizma hidratacije, dodavanjem GO betonu poboljšavaju se njegove mehaničke performanse, izdržljivost, samozarastanje i druge multifunkcionalne karakteristike. Ova studija predstavlja ispitivanje svojstava betona sa dodatkom GO. Pripremljena su četiri različita projekta betonske mešavine. GO je dodat u količinama od 0,01, 0,02, 0,03 i 0,06 %. Hidratacija je analizirana diferencijalnom termičkom analizom. Praćene su mehaničke čvrstoće u trajanju od 28 dana i otpornost na mraz sa solima za odleđivanje tokom 56 ciklusa

Discover Sustainability Journal

Uređivanje međunarodnog naučnog časopisa; Uređivanje tematskih monografija - na godišnjem nivou https://link.springer.com/journal/43621/editors https://portal.issn.org/resource/ISSN-L/2662-998

An Analysis of Transition Temperature for Real and Simulated Heat Affected Zone of HSLA Steel

The aim of this paper is to present the analysis of the influence of different test temperatures on the impact toughness of the real heat affected zone (RHAZ) and the simulated heat affected zone of the welded joint (SHAZ) of high strength low-alloy steel. Through thermal cycle simulation, which includes heating to a certain temperature and programmed cooling, the microstructure of different areas of the heat-affected zone was obtained on the samples, which allows us to directly draw appropriate conclusions regarding the real heat-affected zone of the welded joint. Based on the previous text, a comparison of the brittleness transition temperature values for RHAZ and SHAZ as a very important factor for structural steels was made. It has been observed that with a decrease in temperature many metals exhibit a sudden decrease in toughness, so the temperature at which the material transits from ductile to brittle fracture is called brittle transition temperature (ductile-brittle transition temperature). This indicator is very important regarding further design and exploitation of welded steel structures