Tatjana Rukavina

Impact of calendering process on nonwoven geotextiles hydraulic properties

The influence of the calendaring process of nonwoven geotextiles on the water permeability normal to their planes, including influence of different loads, as well as pore characteristics investigated by two different methods has been studied. Methods of pore characteristics differ in obtaining different pore parameters. Two groups of samples were produced whereas first group is bonded by needle punching, while second group is needle punched samples taken from first group and additionally bonded by calendaring. Mass per unit area for both groups is in range of 150 to 500 g/m2, with increasing by 50 g/m2 for the next sample within groups. Calendaring process decrease water permeability of geotextile, but also decreases interval of geotextile water permeability change due to the applied pressure. Calendared geotextiles have controlled and predictable compressibility, respectively structure which will not significantly change in the practical application.

Application of GPR and FWD in Assessing Pavement Bearing Capacity

Abstract The process of pavement maintenance and rehabilitation starts by collecting the data which will form the base for evaluation of pavement functional and structural condition. Collection of data can be performed by destructive and non-destructive testing. Usually preferred are the non-destructive methods, that do not damage the pavement, and the process of pavement evaluation is objective and repeatable. Non-destructive testing methods are becoming more and more popular, especially for assessing the structural condition of the pavement. Non-destructive testing by a Falling Weight Deflectometer (FWD) and the analysis of so collected data by the process of backcalculations is today the usual tool for assessing pavement bearing capacity. One of the basic input parameters for analysis of the data collected by FWD is pavement layers thickness. The practice in Croatia is to determine pavement layers thickness by coring. This destructive method affects pavement integrity, so the number of such tests should be kept to the minimum. By coring the accurate thickness of all pavement layers is obtained on specific point locations. Thus, numerous deviations in layer thickness remain unnoticed, and in the end, use of such data for the process of backcalculations does not provide ac urate values of layer moduli. Coring can be replaced with non-destructive method of testing by Ground Penetrating Radar (GPR), which provides continuous information on thickness of all pavement layers. The paper shows the method for assessing the bearing capacity of the pavement based on the data collected by FWD, GPR and coring. The calculation for layer moduli was performed by the ELMOD software, separately for the layers thickness data obtained by coring, and separately for the thickness obtained by GPR tests. Analysis and comparison of the results of calculated elasticity moduli obtained by using various methods for collecting layer thickness data were performed in the paper.

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.

Proposal for the value of permitted tolerance on width of grooved rails

This paper describes a research in geometry of grooved rails (type Ri 60/R10). The research was carried out in the last seven years (from 1994 to 2001). The measuring of rails geometry was done before building-in of the rails in to the tramway track or during the supervision grooved rails of production in the factory. Special attention was given to the width guide of grooved rails because the technical specifications for grooved rails (VDV OBERBAU Richtlinien) have not defined permitted tolerance for a guide width of grooved rails. Therefore, some difficulties arise from this fact, during production and supervision of grooved rails in the factory. The results of research can serve as a recommendation for the value of permitted tolerance of the guide width of grooved rails. The results can also be applied as a proposal in the setting of European Standard for grooved rails.

The Effect Of Tram Track Permanent Way Closure System On The Level Of Noise

The paper deals with the analyses results of the noise level measurements carried out on the five different types of tram track permanent way closure while varying the following key parameters: load, speed and the type of the tram vehicle. The study involves the performance of the tram vehicles that are operating in the city of Zagreb. Measurement results were used for the choice of the system of the tram track permanent way closure. In addition to the noise level, the criteria included the economy of the performance and maintenance as well. The choice refers to the tram track closure system that is not separated from the road traffic, which means that the same traffic surface is shared by the road and tram vehicles. The next closure system proved to be optimal for the tram tracks in a separated lane.

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].

The Impact of Tram Track Fastening Systems on Noise Level

The paper presents the results of measurements of noise levels caused by traffic (tram and road traffic) in Drziceva Street in Zagreb (Croatia). Noise level measurements were conducted in cooperation with the City Office for Construction and the Zagreb Streetcar Company (ZET). The tram track in Drziceva Street represents one of the main connecting routes between the northern and southern parts of the city (a length of approximately 4km). The tram tracks are in a separate traffic area. They have been laid on a continuous concrete base and covered with crushed stone. The greater part of the tram track was constructed using the Zg 3/2 system (a direct elastic fastening system), whereas the remainder of the tram track was constructed using the DEPP system (indirect elastic fastening system). Noise level measurements were conducted at two measuring points (one measuring point was chosen for each of the fastening systems). Short-term noise level measurements were executed: two measurements in the daytime period (morning and afternoon), one measurement in the evening and one in the nighttime period. Speed and tram types were taken into consideration during result analysis, as well as geometrical irregularities of the rail running surfaces, the number and category of road vehicles and noise level protection measures already implemented. The conducted measurements have served to compare tram track fastening systems with noise level propagation when trams communicate the route. The results of the research have been of assistance in defining the extent of tram impact on noise level increase (dependent on type and speed of these) in comparison with that of road vehicles communicating the very same route. For the covering abstract see ITRD E129315.

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.