Audrius Vaitkus

Advanced shear tester for evaluation of asphalt concrete under constant normal stiffness conditions

This paper presents motivation and details on the development of an advanced shear tester (AST) device capable of investigating the response of 150-mm cylindrical specimens under constant normal stiffness (CNS) conditions. Based on the laboratory experience and field observations from the soil and rock engineering, CNS conditions are particularly desirable when the normal stress changes considerably during the shearing process. Such situations occur in asphalt pavement structures especially under certain loading configurations. The CNS conditions are complementary to the constant normal load conditions that are applied in the current shear-mode devices incorporated in testing of asphalt concrete (AC) and pavement interface properties. This paper demonstrates the complex state of stress in the upper AC layer of a typical pavement under moving truck wheel and shows the need for the CNS device. In addition to outlining unique AST design features, this paper presents also the verification effort conducted on the solid Ultra-High Molecular Weight Polyethylene specimens. The AST results matched very well the reference data that were obtained under the elastic regime in the stress-controlled mode from the unconfined uniaxial compression and indirect tension tests. Finally, this paper demonstrates the example results collected on the solid AC specimens prepared with two different nominal maximum aggregate sizes. The analysis confirmed the ability of the AST device to capture both practical and fundamental phenomena occurring during the shearing process in the AC. It is believed that AST-type devices that are rather simple in design yet allow to induce complex state of stress in the AC specimens should be more recognised in the future research efforts.

Monitoring the Mechanical and Structural Behavior of the Pavement Structure Using Electronic Sensors

Over the last decade, pavement instrumentation has become an important tool for monitoring the performance of pavement structures and materials under real climatic and traffic conditions. Stress, strain transducers, loop profilers, temperature, and moisture sensors could be reasonably used for sophisticated analysis of pavement performance. Commonly, such research projects involve only few pavement structures under accelerated loading tests. The unique experimental road section was constructed in 2007 in Lithuania. It consists of 27 different flexible pavement structures and all necessary electronic sensors. This road is affected by real climatic conditions and high-intensity heavy vehicle traffic. The aim of such research is to continuously monitor performance of different pavement structures and to elaborate on the most suitable and economically effective pavement structures.

Laboratory study on the influence of casting on properties of ultra-high performance fibre reinforced concrete (UHPFRC) specimens

AbstractThis paper presents a study on the effects of casting procedure and resulting fibre orientation on the properties of Ultra-High Performance Fibre Reinforced Concrete (UHPFRC). To investigate the impact of fibre orientation in the UHPFRC specimens, three approaches were employed. First, densities were measured from the top, middle and bottom zones of the cylinders to observe physical changes as the function of cylinder height. Secondly, two engineering fracture tests were performed in both compression and tension, and a comparison of fracture energies was conducted between different cylinder zones. While previous studies have explored the influence of steel fibres on the UHPFRC performance, the Semi-Circular Bending (SCB) and Disc Compact Tension (DCT) experimental setups have not yet been used in the UHPFRC fracture testing. Lastly, samples from different zones were scanned using X-ray computer tomography (X-ray CT). Both visual and digital image analysis of the X-ray scans were conducted in order...

Research of snow melting materials performance efficiency for road winter maintenance

AbstractIn 2012, the Lithuanian Road Administration initiated a three-year research project ‘The study of effective winter road maintenance of national significance roads in Lithuania’. The main purpose of this research was to optimize road maintenance in winter and to determine the most effective means of combating slippery conditions. The research project was carried out by two institutions: the Road Research Institute of the Faculty of Environmental Engineering of Vilnius Gediminas Technical University and JSC ‘Problematika’. JSC ‘Problematika’ conducted exploratory experiments, which were divided into two phases. In the first phase of the experiment, five different snow melting materials (Slipperiness Reducing Materials – SRMs) were investigated in the laboratory. Different test methods were used in this investigation. In the second phase of the experiment, three SRMs with different properties were selected, and experimental road sections were set up to determine the road slipperiness and the change i...

Performance of Soft Asphalt and Double Otta Seal within First Three Years

Gravel roads play an important role in the transport infrastructure. However, their maintenance (especially the control of dustiness using chemical dust suppressants) is expensive. Besides, the condition of gravel roads results in low driving comfort, longer travelling time, faster vehicle amortization, and so forth. Typically, these problems are solved by paving gravel roads with asphalt wearing layer. However, north countries practice had shown pavement structure high susceptibility to frost due to insufficient thickness of frost resistance layer. The construction of thicker frost resistant layer increases road construction cost by 25% and, in most cases, there is no need to increase bearing capacity by increasing total thickness of pavement structure. In 2012 19 gravel roads were constructed using cost effective rehabilitation technologies—soft asphalt and double Otta Seal in Lithuania. This paper focuses on those two technologies’ performance within first three years of constructed roads exploitation. The implemented experimental research consisted of three parts by evaluating constructed roads base layers bearing capacity; pavement roughness; and pavement distresses and defects. As a result, the acceptable performance indicators were determined for both technologies—soft asphalt and double Otta Seal. Also recommendations for construction and exploitation improvement were defined.

Soft Asphalt Pavement – Solution for Low-Volume Roads in Changing Climate and Economy

In Lithuania, it has always has been an important issue to find durable and cost-effective solutions for paving low-volume roads. The conventional asphalt concrete structures were built using paving grade bitumen with the penetration of 70/100 or 100/150 over the recent 20 years. The performance of those pavements was satisfactory. As an alternative solution, the use of soft asphalt pavements was proposed. This technology is widely used in Nordic countries. But in Lithuania it has never been applied. Research on the designed soft asphalt mixtures was carried out and the trial on-site sections were constructed. The results of laboratory tests and on-site research were positive and promising. Based on that, the technology could be considered as successfully implemented and good quality was achieved.

Performance of Pavements Affected by Static and Impact Load

Pavements of airdromes, ports and container terminals, logistics terminals, industrial areas, parking lots, waste recycling areas and etc. are affected by static and impact loads. These kinds of loading differ from typical loading of roads. Due to it, pavements affected by static and impact load are design by special models according to the main distresses – permanent deformations and thermal cracking. For this purpose, there are discussed characteristics conditioning performance of pavements affected by static and impact load.

Optimized Asphalt Mixtures for Noise Reduction in Lithuanian Roads

In the world of growing economy and population, the need of transportation is rapidly increasing also raising problems of noise pollution. Environmental noise levels are increasing in parallel with increasing traffic flows resulting negative effects for society, wildlife and economy. The article gives an overview about the main transport noise source tyre/road noise, its generation mechanisms and influencing factors. One of the most effective and promising tyre/road noise solutions is low noise pavements, which has different noise reduction approaches. Low noise asphalt pavements and theoretical noise reduction principles are analysed in the paper as well as the development experience of particular low noise asphalt pavements for Lithuanian conditions.