Sanja Dimter

Strength properties of fly ash stabilized mixes

ABSTRACT A laboratory investigation of the properties of cement-stabilized pavement base course materials consisting of sand from the river Drava stabilized by hydraulic binder made of cement and fly ash is presented. The goal of the investigation was to determine the influence of several factors on the compressive and indirect tensile strengths. The factors included: a change in the structure of the stabilized mixes, a change in the treatment temperature and the time used in the sample treatment. The hydraulic binder was prepared using different percentages of fly ash in the binder: 0% (control mix), 25%, 50%, and 75%. It was determined that the amount of fly ash strongly influences the strength of the stabilized mixes. Increasing the amount of fly ash in the binder leads to a decrease in the compressive and indirect tensile strengths.

Elastic properties of cement-stabilised mixes with steel slag †

In this study, we evaluated the elastic and mechanical properties of a new type of cement-stabilised material made with steel slag, varying the content of cement and steel slag. To study the elastic properties of these mixes, we measured their density, compressive strength and ultrasound pulse velocity at curing ages of 7, 28 and 90 days. The aggregate type and curing age greatly affected the elastic properties and varied much depending on the cement content. The Poissons ratio chosen in analyses had little influence on the dynamic modulus. Various expressions given by building codes were used to predict the elastic properties of the mixtures. These codes generated very different values of the static modulus of elasticity, making most of them unsuitable for predicting the elastic properties of cement-stabilised materials. Using our experimental data, we provide the best combination of existing equations to predict elastic properties, and we conclude that measuring the ultrasound pulse velocity is a suitable way to predict the mechanic and elastic properties of cement-stabilised materials.

KRUŽNA RASKRIŽJA – SUVREMENI NAČIN RJEŠAVANJA PROMETA U GRADOVIMA

Izgradnja kružnih tokova intenzivirana je posljednjih 20 godina u svim europskim zemljama. U skladu s tim, ovakva raskrižja i u Hrvatskoj dobivaju

Characterization of cement stabilized pavement layers with ultrasound testing

Performance of ultrasonic pulse velocity (UPV) in hydraulically bound mixtures is examined as a non-destructive testing, in order to estimate its pote

Elastic properties of fly ash-stabilized mixes.

Stabilized mixes are used in the construction of bearing layers in asphalt and concrete pavement structures. Two nondestructive methods: resonant frequency method and ultrasonic pulse velocity method, were used for estimation of elastic properties of fly ash–stabilized mixes. Stabilized mixes were designed containing sand from the river Drava and binder composed of different share of cement and fly ash. The aim of the research was to analyze the relationship between the dynamic modulus of elasticity determined by different nondestructive methods. Data showed that average value of elasticity modulus obtained by the ultrasound velocity method is lower than the values of elasticity modulus obtained by resonant frequency method. For further analysis and enhanced discussion of elastic properties of fly ash stabilized mixes, see Dimter et al. [1].

COMPARISON OF PAVEMENT STRUCTURES IN TUNNELS

Tunnels pose many fire risks. It is difficult to fight fires in tunnels due to their limited accessibility, the quantity of smoke, and high thermal radiation. Temperatures in tunnel fires can reach 1000 °C, and these fires can spread quickly and persist for long periods, the longest recorded in Europe lasting 53 h. The main requirements of tunnel pavement structures are driving safety and comfort, as well as low construction and maintenance costs. Choosing between using concrete or asphalt pavement structures in tunnels requires the assessment of many criteria, including safety, cost, ecology, and energy use. One must also consider the availability of technologies (finishers) and resources (bitumen or cement), as well as the probability of achieving the required contractor experience level, which impacts pavement management. This paper describes our analysis and process for deciding the pavement structure to be used in tunnels, as well as current European technical regulations for safe traffic flow in tunnels.

Application of an artificial neural network in pavement management system

The era of intensive construction of new roads is behind us, so road agencies are now focused on maintaining and preserving existing pavement surfaces. As they are faced with limited founds for maintenance it is important to utilize the money by selecting the best maintenance strategy. Selection of appropriate maintenance strategy is a complex task which includes factors such as current condition of the pavement, road classification, traffic volume and type of pavement distress. These factors can be automated and implemented in pavement management systems to achieve standardised approach to road pavement assessment and management. One of the key components of a pavement management systems are pavement performance prediction models which simulate pavement deterioration process and forecast its condition over time, one of such model is artificial neural network. This paper analyzes the possibility of using artificial neural networks in pavement management systems for evaluation of existing pavement condition and its possible application for defining the maintenance strategy of state roads. Backpropagation algorithm was applied on 481, 3 km of state road in Osijek-Baranja County which represents 7% of total length of national road network in Croatia. Obtained results indicated that artificial neural networks can be used for optimization of maintenance or rehabilitation strategies as well as assessment of pavement condition at project and network level.

Contemporary approach to engineering education in the field of transport infrastructure

The current legislative and regulatory framework in the field of higher education as well as the Education, Science and Technology Strategy directs the education of construction engineers towards construction innovations, new design concepts, technologies, and materials according to globally set goal - resource saving. These requirements demand the application of contemporary teaching methods like learning through work, research, putting into function learned concepts, using acquired knowledge and skills in actual examples, learning in the context of division of work and communication with other participants in teaching. This education approach is realized within the course of the Substructure of Transport Infrastructure, compulsory course at the first year of graduate study at the Faculty of Civil Engineering Osijek. The aim of the course is to familiarize students with the design and construction of the lower structure of roads and facilities therein, technology planning and the quality control of works. Familiar, classical performances of lectures and exercises are complemented with workshops, independent work of students in the laboratory, independent work on computer programs, field teaching and participation of practitioners as guest lectures. An important part of the knowledge acquisition is the work in the laboratory where, apart from getting to know how to use the equipment, students perform the standard Proctor’s experiment. That way, they extend the theoretical knowledge of Proctors experiment, remove possible confusion and understand the standards requirements that determine the experiment and make the results relevant. This paper describes the contemporary approach to the education by analyzing the concept of Substructure of Transport Infrastructure course.

The contribution to the urban heat islands exploration: underpasses and their elements

ABSTRACT Final and other layers of road structures and their corresponding elements significantly affect the generation of heat islands in areas in which they are located Air temperature increases in relation to the surrounding areas during the formation of heat islands. This paper presents the results of field research which measured the temperature of all elements of two road underpasses, which are integral parts of the D7 (E73) state road in the city of Osijek, the Republic of Croatia. The tests were conducted from April to November 2014. The aim of the performed tests was to determine the effects of solar radiation on the temperature of constituent elements of road underpasses. The measurements were performed with the aim of determining the dependence of location of individual elements of the construction in space and material properties of which the same are made. The obtained test results indicate that the temperatures of the observed elements of the road underpasses significantly vary depending on the position within the construction, surface albedo and external weather conditions.

Possibilities of bioash application in road building

Biopepeli su neizbježan proizvod ispunjavanja zahtjeva za sve vecom primjenom obnovljivih izvora u proizvodnji energije. Ekoloski i ekonomski prob