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The use of reclaimed asphalt has become a common practice and necessity in many developed countries whereas there are several options how to deal with elevated content of such material which is typical for some level of degradation and heterogeneity. Well-developed and widely used are solutions where reclaimed asphalt is cold fed by up to 20%. Higher portions of reclaimed asphalt are still challenging and need additional focus. Quite common in last few years is use of rejuvenators which are understood as special chemical compounds which help to partly restore the degraded bitumen and secure sufficient performance behavior of asphalt mix containing higher portions of reclaimed asphalt. Recent study focused on use of several market established rejuvenators and some newly developed variants which are predominantly based on renewable materials. A typical asphalt concrete AC16 has been selected and 50% natural aggregate was replaced by reclaimed asphalt of 0/8 mm grading. Rejuvenators were added in a content of 5–7% of the bitumen content presented in the reclaimed asphalt. Several tests have been performed focusing on water susceptibility, deformation behavior (stiffness) and resistance to crack propagation. At the same time bitumen extracted from the reclaimed asphalt was mixed with rejuvenator and selected bitumen tests were done to find some relation between binder and asphalt mix behavior.

The paper describes the situation in BIM implementation in public projects in the transport sector within global powers and the Czech Republic, emphasising the specificities of the construction market and legislation base in the Czech Republic. The specialised part presents the proposed methodology of BIM implementation in road construction, and demonstrates the different levels of detail and information using a BIM model. Last but not least, there is a risk analysis and the risks identified are briefly introduced.

The lifetime cost and environmental footprint of asphalt pavements hugely depend on their durability. It is widely accepted that water action plays a crucial role in the deterioration of hot mix asphalt concretes. Researchers seek solutions for promoting adhesion between bituminous binders and aggregate to avoid debonding (stripping) due to the presence of water and mechanical loading. In this research study, five different adhesion promoters were studied at multiple scales. The impacts on bituminous binders, their interactions with water and aggregates, and macroscopic properties of a selected type of asphalt concrete were assessed using both custom and standardized experimental test methods. The study revealed that the performance of additives cannot be assessed based on the results of a single test. A correlation was found between bituminous binder adhesion to aggregates, fracture-mechanical properties of asphalt concretes, and their susceptibility to deterioration in mechanical properties. The results indicate that silane-based adhesion promoter holds the biggest promise for increasing the resistance to stripping in asphalt concrete pavements.

Sleep is important for the development of preterm infants. During sleep, neural connections are formed and the development of brain regions is triggered. In general, various rudimentary sleep states can be identified in the preterm infant, namely active sleep (AS), quiet sleep (QS) and intermediate sleep (IS). As the infant develops, sleep states change in length and organization, with these changes as important indicators of brain development. As a result, several methods have been deployed to distinguish between the different preterm infant sleep states, among which polysomnography (PSG) is the most frequently used. However, this method is limited by the use of adhesive electrodes or patches that are attached to the body by numerous cables that can disturb sleep. Given the importance of sleep, this review explores more unobtrusive methods that can identify sleep states without disturbing the infant. To this end, after a brief introduction to preterm sleep states, an analysis of the physiological characteristics associated with the different sleep states is provided and various methods of measuring these physiological characteristics are explored. Finally, the advantages and disadvantages of each of these methods are evaluated and recommendations for neonatal sleep monitoring proposed.

Knowing the relationship between the stiffness modulus and the empirical mechanical characteristics of asphalt concrete, road engineers may predict the expected results of costly laboratory tests and save both time and financial resources in the mix design phase. In fact, such a model would make it possible to assess a priori whether the stiffness of a specific mixture, characterised in the laboratory only by the common Marshall test, is suitable for the level of service required by the road pavement under analysis. In this study, 54 Marshall test specimens of high modulus asphalt concrete were prepared and tested in the laboratory to determine an empirical relationship between the stiffness modulus and Marshall stability by means of shallow artificial neural networks. Part out of these mixtures was characterised by different types of bitumen (20/30 or 50/70 penetration grade) and percentages of used reclaimed asphalt (RAP at 20% or 30%); a polymer modified bitumen was used in the preparation of the remaining Marshall test specimens, which do not contain RAP. For the complex and laborious identification of the neural model hyperparameters, which define its architecture and algorithmic functioning, the Bayesian optimization approach has been adopted. Although the results of this methodology depend on the predefined hyperparameters variability ranges, it allows an unbiased definition of the optimal neural model characteristics to be performed by minimizing (or maximizing) a loss function. In this study, the mean square error on 5 validation folds was used as a loss function, in order to avoid a poor performance evaluation due to the small number of samples. In addition, 3 different neural training algorithms were applied to compare results and convergence times. The procedure presented in this study is a valuable guide for the development of predictive models of asphalt concretes’ behaviour, even for different types of bitumen and aggregates considered here.

High-modulus asphalt concrete is a specific type of asphalt mixture which is used for several decades in pavement engineering. It was originally invented as a solution which should help to minimize the effects of permanent deformation caused mainly by heavy traffic and mainly during the periods with elevated temperatures. These mixtures are used either in binder or base courses, whereas for base courses, it is important to combine reasonably the high stiffness with good fatigue life to avoid premature pavement failures not caused by rutting but by fatigue cracking. In this respect, various types of HMAC used and designed in the Czech Republic were tested first and foremost to determine stiffness. The stiffness modules were tested according to EN 12607-26, test method IT-CY, at selected temperatures representing cold, moderate and high service temperatures. The susceptibility to temperature change can be shown by thermal susceptibility for each mixture. In the parallel test, specimens were laboratory age to identify the changes in stiffness caused by thermo-oxidative ageing. This allows calculating a simple measure of the ageing index. Not presented in this paper but performed as a very last test was resistance to crack propagation.

The usage of certain amount of reclaimed asphalt (RA) is a well-established trend, which can be seen in many developed countries. Regrettably there are some countries or regions which still have very strict standard restrictions about RA usage in asphalt mixtures, mainly in surface layers. For example in current technical standards in the Czech Republic the use of RA in stone mastic asphalt mixtures or asphalt concrete for premium surface layers is banned. Recycling of construction materials saves direct primary costs like new material purchasing and at the same time also facilitates savings of other costs like energy, material disposal and transport etc. Those factors are connected to environment-friendly approaches, primarily in the case of emission and greenhouse gas production reduction. Material disposal can subsequently be reduced solely to waste or by-product materials which have no way of further utilization.

In developed countries there is a clear shift from new pavement structures to rehabilitation works which usually use the mill and fill method by replacing some of the asphalt layers. This process on one hand creates material which has to be milled and on the other hand requires new material for producing asphalt mixtures which are used back to the pavement structure. To improve the economic efficiency and reduce environmental impacts reuse or recycling are presently supported in elevated extent. To make the highest possible use of reclaimed asphalt rejuvenation is seen as one of the options. On the other hand excessive heating of reclaimed asphalt should be avoided to not overburn the bitumen or even to avoid additional ageing of already aged material. Combining effects of rejuvenation and warm mix technologies seems as an interesting option. In this respect a trial section was designed including 13 different options of warm mix asphalt with 0–50% reclaimed asphalt. The asphalt mixtures differed in amount of used reclaimed asphalt (RA) 0/11 mm (0%, 30% and 50%), the gradation of used paving grade bitumen (50/70,70/100) and warm mix asphalt additives or used techniques. In asphalt mixtures there were used bituminous binders with selected low temperature additive, which have primarily the function of reducing the production temperature, or the benefit in terms of improving the properties of the asphalt mixture, the adhesion improvement (in some cases) and in at least one of the cases the potential for reducing the characteristic odor of asphalt mixtures. Additives based on organo-silanes and different types of synthetic waxes (FT paraffin, amide wax, PE wax) have been used. Additionally foamed bitumen technology was applied as well. The asphalt mix performance was assessed by term of stiffness, resistance to permanent deformation, water susceptibility and thermal induced as well as fatigue cracking. The key findings will be presented by the paper.

Bitumen-aggregate adhesion is one of the crucial characteristics related to an asphalt mix. It affects the mix durability mainly in terms of its moisture susceptibility. Wide range of adhesion promoters is available to the market and can be used in regular practice, nevertheless usually only limited attention is paid to the long term activity (mainly the effective substances) and stability of the additives in the bitumen and the asphalt mix. Research done at the Czech Technical University in Prague is focused on studying the impact of differently aged asphalt mix using selected procedures defined in prEN 12697-52 as well as developing a self-defined procedure by applying the PAV equipment used since many years for long-term bitumen ageing. The results of aged mixtures were always compared to unaged control mixes. In parallel use of aged bitumen was assessed as well. The results were further compared to a simple adhesion test to get a more complex understanding of the activity of selected additives. In total more than 5 additives were selected and tested on one type of asphalt concrete with the application on a more hydrophilic aggregate type. Results gained during this experimental study are presented in the paper using as a criterion indirect tensile strength ratio determined either by EN 12697-12 or by modified procedure according to AASHTO T283. In parallel because of elevated temperatures used during ageing suitable covering of cylindrical test specimens was analyzed as well to avoid unnecessary deformations or even disintegration of the tested specimens. For this reason two types of protective collar were chosen – PVC and thin steel mash – in both cases fixed by plastic belts. It is assumed that steel mash can better simulate the effect of ageing keeping the envelope partly free for direct contact with hot air and pressure. Results of this comparison are presented in this paper as well.

Highly important issue related to good pavement quality and job performance is in case of asphalt mixtures the compaction rate of asphalt layers. Compaction rate is a factor which has very significant impact on the durability, strength properties, resistance to cracking, etc., of asphalt pavements. Even though the compaction rate influences the lifespan of a pavement, it is very often neglected or the attention which is given to proper compaction is not sufficient enough. In this experimental study the asphalt mixture test specimens were compacted at different temperatures and using different compaction energies to evaluate the influence of poor compaction rate on the mixture properties. The chosen tested mixture was asphalt concrete for wearing courses with maximum particle size of 11 mm. The specimens were compacted on Marshall impact compactor by different amount of blows. The stiffness modulus at three, respectively, four testing temperatures was measured on all of the specimens. Additionally, some of the test specimens were exposed to artificial laboratory ageing to evaluate the effect of compaction rate to fatigue resistance of the mixture. The result shows very strong dependence between compaction rate and decrease of stiffness modulus.

Within the actual transnational road research programme of Conference of European Directors of Roads (CEDR) project COREPASOL (Characterization of Advanced Cold-Recycled Bitumen Stabilized Pavement Solutions) will be supported in the period 2013-2014. This project is realized by an international team of Czech Technical University in Prague, University of Kassel, University College Dublin, Laboratorio Nacional de Engenharia Civil, I.P. (LNEC) and industrial partner Wirtgen GmbH. The project focuses mainly on harmonizing mix design of cold-recycled bitumen stabilized materials following the existing scientific and engineering experience and approaches. The key objective in this relation is to develop and recommend comprehensive mix design and characterization by studying compaction methods, curing procedures and performance tests. Besides the overall focus of the project COREPASOL partial results on comparison of compaction methods used for preparation of test specimens for cold recycled mixes are presented.

One of today's most commonly used test on a Dynamic Shear Rheometer (DSR) is the Multiple Stress Creep Recovery (MSCR) test. The test is described in the standard EN 16659, which is valid in the Czech Republic since October 2016. The principle of the test is based on repeated loading and recovering of a bitumen sample, according to which it is possible to determine the percentage of elastic recovery (R) and non-recoverable creep compliance (Jnr) of the bituminous binder. This method has been recently promoted as the most suitable test for assessing the resistance of bituminous binders to permanent deformation. The test is performed at higher temperatures and is particularly suitable for modified bituminous binders. The paper deals with the comparison of the different input parameters set on the DSR device - different levels of stress, temperature of test, the geometry of the measuring device and also a comparison of the results for a different number of loading cycles. The research study was focused mainly on modified bituminous binders, but to compare the MSCR test it is performed even with conventional paving grade binders.

One of the environmentally most important factors of asphalt pavements is the energy demand necessary due to satisfactory workability and compactability of an asphalt layer. Economical energy consumption on one hand and sufficient quality of asphalt pavements on the other hand can be seen as important factors of its sustainability. Both characteristics have therefore crucial role in the so called environmental compatible pavement structure. There are several possibilities or techniques how energy demand can be reduced and durability preserved or increased. Important set of these techniques, called warm asphalt mixes has been in this respect developed during the last ten years in Europe and the United States. There are several possibilities, how these mixes can be produced.The paper presents warm asphalt mixes experimentally prepared and assessed with various additives of synthetic waxes or polyphosphoric acid. For the experimentally prepared asphalt mixes a comparison of their mechanical as well as rheological properties is summarized and discussed.

In road construction various recycling techniques are well-known and long-term developed worldwide. Commonly recyclable materials, known as reclaimed asphalt pavement, are used. These materials are gained during the pavement rehabilitation process. In some cases further secondary granular materials are used, e.g. masonry or concrete recyclable material (MRM or CRM) coming from demolition works. Utilization of recyclable materials in pavement structure is specified in Czech Republic by technical requirements, focusing above all on recycled asphalt pavement (RAP), lesser then on other granular materials especially for the sub-base layers. The trend is to use recyclable materials in one structural layer of the pavement.Authors are introducing experimental design of an alternative pavement structure, where the recyclable materials are used in protection layer, sub-base and/or binder course all at once, eventually in wearing course as well. The main techniques are: MRM reinforced by synthetic fibres and cold recycling technique with RAP, bituminous emulsion (or foam bitumen) and cement as combined binder. Pavement rehabilitation techniques based on cold processes are from the environmental and economic point of view without any doubt of benefit. The paper summarizes the present laboratory experience with these techniques and comments results of experimental tests of odd structural materials and the pavement structure with both materials. Strength properties as well as stiffness and cohesion of two layers made by different technique is introduced and discussed.

The use of fly-ash stabilizers, materials from fluidized combustion fly-ash, and other solid coal-burning residues, which are called coal combustion by-products (CCB), have good potential for application in subgrade structures and roadbed materials of roads as well as in the structural pavement layers. One of the many factors limiting the application of some CCB sorts is the relatively low resistance in repetitive contact with water, volumetric changes, and the risk of partly unsatisfactory hygienic and environmental parameters. With respect to the aforementioned negative characteristics of CCB, which occurred primarily under the repetitive impact of water and freezing, the experimental examination focused on improving CCB resistance to frost and water, verification of volumetric changes, and improvement of pozzolana characteristics of CCB by increasing the percentage of fine particles in the original material (e.g., by means of mechanical and/or chemical activation, including combination of both types). At the same time, the road construction industry strives to find a suitable substitute for the traditionally applied hydraulic binders as well as expand the existing base of the binders applied. The experience with using CCB as a binder or binder component has not been as extensive so far as to allow any generalisation of conclusions. Therefore, the possibilities of applying alternative additives as a replacement for the binders traditionally applied have been researched. Another application of the coal combustion by-products tested was in cold recycling mixes. In this case, the fly-ash from fluidized combustion is used as a substitute for the hydraulic binder. The fly-ash tested was subjected to mechanical activation, while the parameters of the mix under scrutiny reflected the impact on the strength and deformation parameters of the mix; last but not least, the water susceptibility indicator was also monitored. From the environmental perspective of practical applicability of the mixes a chemical analysis and leaching tests have been done.