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This paper presents the results of tests of physical-mechanical, durability and microscopic properties of geopolymer mortar mixtures based on fly ash and ladle slag. The mixtures are alkali-activated using sodium silicate and sodium hydroxide solution. Firstly, the effects of different fly ash (class „F“) particle sizes on the characteristics of the mortar mixtures were examined when binder and alkali activator were cured at 95ºC for 24 h, also pozzolanic activity and strength activity index were investigated. After that, fly ash ground of optimal particle sizes (0,09 mm) was replaced with ladle slag, 0 to 20% of the mass, the replacement steps being 5%. The specimens having dimensions 4x4x16 cm were then cured in ambient conditions, and the effects of replacement of a part of fly ash with ladle slag were determined by testing water absorption, flexural and compressive strength, freeze-thaw resistance, sulfate attack, ultrasound velocity, FT-IR spectroscopy and leaching of heavy metals. According to the test results of compressive strength resistance of geopolymer mortars exposed to sulfate solution, the mortar made with fly ash and ladle slag showed better resistance to sulfate attack than the mortar made with fly ash only.

Porous or pervious concrete was in use since the 60's of the previous century. It was first used in the USA and afterwards in Europe. The environmental importance of pervious concrete can be seen through fast collection of stormwater from the pavements, parking lots and other impervious surfaces. . Special purification systems remove the detrimental matter from the collected strormwater. As such, it can be used for other purposes. The pervious concrete has little or almost no fine aggregates. Its porosity is high, and ranges between 15 and 30 % in comparison to the concrete volume. Prior to massive usage of pervious concrete, it was necessary to prove, i.e. to examine its properties in service conditions. The paper elucidates the environmental character of pervious concrete, provides its usual composition and its properties.

In the spirit of the sustainable buildings, and with the goal of protection of river courses, in the near future an already announced directive ordering closing down of a large number of river aggregate dredging operations will be adopted. For that reason, usage of crushed mineral aggregate in concrete mixes is increasing. Irrespective of downsides of the fined crushed mineral aggregate, such as the presence of fine particles bordering the upper permissible limit and the unfavorable shape of the grain of the course aggregate for obtaining liquid consistency required for the pumpable concrete, the demanded pumpability of concrete during transport and placement has been achieved. By adding admixtures to concrete, the required concrete properties, such as: frost resistance, simultaneous frost and salt resistance and water tightness have been achieved. [Projekat Ministarstva nauke Republike Srbije, br. TR 36017: Utilization of by - products and recycled waste materials in concrete composites in the scope of sustainable construction development in Serbia: investigation and environmental assessment of possible applications]

One of the essential requirements in modern civil engineering is a sustainable building, with the aim of reducing the harmful impact on the environment. Since the early XXI century, usage of recycled materials has been insisted on, which could, at least partly, substitute traditionally used materials. Although there is no serial manufacturing of TV sets with cathode ray tubes anymore, piles of cathode ray tube glass (CRT) at the waste disposal sites have still been on the increase. This experimental research was supposed to determine the potential for using subtly milled CRT glass as a supplementary cementitious material and to check the resistance of similar concretes to the sulphate action. Six testing concrete batches were made. The percentage of cement replacement percentage with CRT was: 5%, 10%, 15%, 20% and 35%, by mass. Durability assessment of concrete to sulphate action was done by visual estimation of concrete appearance as well as through testing the compressive strength variations of treated concrete specimens 3, 6, 12 and 36 months old. After soaking the specimens in a 5% solution of Na2SO4 for 36 months, concretes with 15% to 20% of replaced cement with finely ground CRT glass have simultaneously satisfactory compressive strength and resistance to sulfate attack. In this sense, this range of replacement of cement with finely ground CRT glass can be recommended for practical application. [ABSTRACT FROM AUTHOR]

The topic of this paper is experimental and numerical analysis of the impact strength of unreinforced concrete slabs. Impact strength of concrete is significant in case of some accidental loads during exploitation. Impact strength can be determined experimentally, using Drop-weight test, Charpy test, Projectile impact test, Explosive test, etc. In this research, a numerical model for determining the impact strength of concrete slabs based on Finite element method (FEM) and high-end engineering software has been proposed. Modelling approach to this problem was applying the Explicit dynamics FEM analysis. Thereat, two different existing material models for concrete were enforced: Concrete damage plasticity model – CDP (implemented in ABAQUS/Explicit software), and the Riedel-Hiermaier-Thoma model – RHT (implemented in ANSYS Workbench software). Analysis parameters for both material models, necessary as input data, have been determined through a series of FEM analyses and validated by performed experiments, using drop-weight test. Results of the numerical analyses have been compared with the experimental ones, as well as mutually. Advantages and drawbacks of both material models are highlighted, as well as the reliability of the proposed numerical models. The proposed numerical FE models, confirmed by experiments, can be successfully used for determining impact strength of concrete slabs in further research. [ABSTRACT FROM AUTHOR]

Caričin Grad is an archeological site dating back to VI century, located in the vicinity of present day Leskovac, Serbia. The city is the legacy of the famous early Byzantine Emperor Justinian I. The city, in the town planning terms, is divided into three large units. Acropolis, Middle town and Lower town, connected by the suburban area. The grandeur and importance of the city are witnessed by the remenants of several lines of city walls, planned street network, cisterns, thermae, aqueduct and sewage, numerous sacral buildings, administrative structures and housing architecture. Considering the complexity of the city, in town planning and architectonic terms, and diversity of building types in it, the mortars taken for analyses were collected from various types of buildings: from housing, public buildings, fortifications and from the aqueduct structure. In the paper, basic physical properties, as well as mineralogic, morphologic and chemical features of the sampled mortars were examined. The testing was performed using optical and scanning electron microscopy, XRF semi-quantitative analysis and XRD (x-ray diffraction). Based on the mentioned analyses, it was concluded that the main binder in the mortar was pulverized brick, which activated its pozzolanic activity. In addition, as an auxiliary binder, there was limestone powder, considering that the mortar contained the crushed limestone aggregates as well. The detected aggregate grains are the river aggregate, pieces of bricks and fine crushed limestone aggregate. These results would be further used for making the mix designs of repair mortars. [ABSTRACT FROM AUTHOR]

Rapid technological and industrial development in the recent decades caused considerable environmental problems, and one of the most significant is, undoubtedly, disposal and recycling of waste materials and by-products of industrial production. Since concrete is a composite material, waste materials can suitably be used in its composition. In this paper, the research of effects of milled recycled glass from cathode tubes, flotation tailings from a copper mine, red mud and fly ash as mineral admixtures on properties of fresh and hardened self compacting concrete was presented. The test results indicated that the addition of such materials does not cause a decline in physico-mechanical characteristics and properties of durability of self-compacting concretes (SCC), and they even improve some aspects of concrete performance in comparison with SCC made with limestone filler as mineral admixture. Waste materials such as fly ash and recycled glass of cathode tubes (CRT) exhibit a puzzolanic activity, so the performances of the concretes with these admixtures proved to be better after ageing than the concretes with other admixtures. [ABSTRACT FROM AUTHOR]

Rapid technological and industrial development in the recent decades caused considerable environmental problems, and one of the most significant is, undoubtedly, disposal and recycling of waste materials and by-products of industrial production. Since concrete is a composite material, waste materials can suitably be used in its composition. In this paper, the research of effects of milled recycled glass from cathode tubes, flotation tailings from a copper mine, red mud and fly ash as mineral admixtures on properties of fresh and hardened self compacting concrete was presented. The test results indicated that the addition of such materials does not cause a decline in physico-mechanical characteristics and properties of durability of self-compacting concretes (SCC), and they even improve some aspects of concrete performance in comparison with SCC made with limestone filler as mineral admixture. Waste materials such as fly ash and recycled glass of cathode tubes (CRT) exhibit a puzzolanic activity, so the performances of the concretes with these admixtures proved to be better after ageing than the concretes with other admixtures. [ABSTRACT FROM AUTHOR]

Felix Romuliana is an archeological site located in the vicinity of Zajeèar, in the east part of Serbia, south of the Danube. Felix Romuliana is a monument of Roman court architecture in the period of the Tetrachy. It is the only archeological site in Serbia, which is under the UNESCO's protection. It is a fortified palace, built at a request of the Roman Emperor Gaius Valerius Maximianus, in the honor of his mother Romula, which is why it was named Romuliana. There are two fortification systems around this palace: and older inner system, and a younger outer system which encompasses the palace, temples, military facilities, storage buildings...Mortar samples were analyzed with the goal of obtaining information about their morphological, mineralogical, chemical and basic physical properties. For an analysis of these properties, optical and scanning electron microscopy were used, as well as XRF and XRD analysis. Depending on the location of the sampled mortars, differences of the individual properties of mortar were observed. The mortar analysis determined that lime was used as a binder. The mortars prevalently consist of the river aggregate grains, crushed limestone aggregate grains and traces of crushed masonry blocks. Further research should be focused on production of repair mortars. [ABSTRACT FROM AUTHOR]

The share of aggregate in concrete composition, in terms of volume is 70%-80%. The properties of fresh and hardened concrete depend on the aggregate properties, primarily on particle size distribution. The paper considered impact of particle size distribution of aggregates from two screening plants from the South Morava river on the properties of concrete. The intention was to make concrete mixtures with the aggregate which would have as identical particle size distribution, as similar consistency of fresh concrete as possible and same compressive strengths. For making of afore mentioned concrete mixes, the same sort of cement and same admixtures were used. It was concluded that the difference in the particle size distribution of aggregate fractions had an impact on the composition of concrete mixes of the identical properties. Specifically, the quantities of cement, admixtures and water were different in the afore mentioned mixtures. The technical specifications of the cement manufacturers include a recommended quantity of cement for specified concrete classes. It is concluded that these values are only rough guidelines. The same holds for the recommended quantities of admixtures. For that reason, every required concrete mixture must be verified in laboratory, i.e., previously tested. [ABSTRACT FROM AUTHOR]

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The potential to use waste glass, including cathode ray tube (CRT) glass, for making new products or as an admixture to existing ones is being intensively investigated. This kind of research intensified particularly in the period after CRT TV sets and computer monitors were replaced in the market by the advanced technology of thin film transistor (TFT) and liquid crystal display (LCD) screens. Cathode ray tube glass represents a considerable part of electronic waste (e-waste). E-waste globally increases at a far higher rate than other solid waste materials. There is a possibility to recycle cathode ray tube glass and use it in the construction industry. This paper shows the test results of physical and mechanical properties of blocks and paving flags. The reference specimen was made with quartz sand, while the other product employed a combination of quartz sand and ground panel cathode ray tube glass. The glass was ground to the fraction 0.25/1.00 mm, which corresponds to quartz sand fineness. The following tests were performed: shape and dimensions, resistance to freeze/thaw and de-icing salts, water absorption, splitting tensile strength and tensile strength by bending. Special attention was paid to the tests of Böhme wear resistance, slip resistance of the top surface of CRT products using a pendulum, radioactivity and leaching. The texture of the experimental concrete products was observed by SEM (scanning electron microscopy) and analyzed. The results obtained by experimental testing unequivocally show that CRT glass can successfully be used for making concrete blocks and paving flags. [ABSTRACT FROM AUTHOR]

This paper presents the testing of the durability of concrete where a part of cement was replaced with ground panel cathode ray tube glass (CRT) finer than 63 µm. The percentage of cement replaced with glass is 5%, 10%, 15%, 20%, and 35%, by mass. The highest percent share of mineral admixtures in CEM II (Portland-composiste cement) cement was chosen as the top limit of replacement of cement with glass. In terms of the concrete durability, the following tests are performed: freeze-thaw resistance, freeze-thaw resistance with de-icing salts-scaling, resistance to wear according to the Böhme test, sulfate attack resistance, and resistance to penetration of water under pressure. A compressive strength test is performed, and shrinkage of concrete is monitored. In order to determine the microstructure of concrete, SEM (Scanning Electron Microscopy) and EDS (Energy Dispersive X-ray Spectroscopy) analyses were performed. The obtained research results indicate that the replacement of a part of cement with finely ground CRT glass up to 15% by mass has a positive effect on the compressive strength of concrete in terms of its increase without compromising the durability of concrete. The results obtained by experimental testing unequivocally show that concrete mixtures made with partial replacement (up to 15%) of cement with finely ground CRT glass have the same freeze-thaw resistance, resistance to freeze/thaw with de-icing salt, resistance to wear by abrasion, and resistance to sulfate attack as the reference concrete. In terms of environmental protection, the use of CRT glass as a component for making concrete is also very significant. [ABSTRACT FROM AUTHOR]