Federal Highway Research Institute

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Concrete pavements

Optimisation of the practical suitability of porous concretes for road construction (08.0266)
For some years now, the optimisation of the noise properties of road pavements has been increasingly pursued in road construction. In this context, research activities on the use of open-pored concretes (OPB) have been intensified again in the recent past. The aim of the investigations was to develop and test an alternative, noise-reducing road surface with high durability by exploiting the special material properties of concrete. In the course of the present project, the requirements for an OPB are to be investigated in comparison with road surface concretes with a dense structure, taking into account different construction methods and service life. As a result, the construction method using OPB as a road surface with improved noise properties is to be brought up to a technical level that for the first time enables the purposeful construction of a test section on a section of a federal road or federal motorway.

Performance-oriented road surfaces with exposed aggregate concrete or grind texture (08.0260)
Due to the constantly increasing volume of traffic, noise pollution from road traffic continues to rise, so that noise protection is becoming more and more important in road planning. In concrete road construction, the production of longitudinal, low-noise textures by means of grinding type S (texture grinding) and type S+ (grinding with grooving) is therefore being investigated and tested as an alternative to exposed aggregate concrete textures. The aim is to develop a process-safe surface texturing for the production of concrete road surfaces with reduced rolling noise. Within the framework of the further development and testing of texture grinding, the tyre-road interaction is also to be investigated. Here, a complex consideration of all pavement surface properties is necessary in order to avoid conflicting goals when optimizing the surface performance. The objectives of this research project are to deepen the understanding of the tyre-road interaction from the point of view of concrete road construction and to optimise the texture properties with regard to the avoidance of the groove wander phenomenon as well as the formation of tyre abrasion.

Sustainable construction methods with concrete pavement - recycling and reuse of concrete (08.0256)
In this research project, the use of demolished concrete for high-quality reuse in road pavements is to be investigated. The aim is to provide an overall view of the current situation of road concrete recycling by means of engineering studies and by considering all process phases and participants: state of the art, problems and obstacles, issues. Existing interrelationships and mutual influences in the overall context of recycling are to be recorded and prepared for manageable consideration in the planning phase. The focus of the project will be on the constructional aspects. With the help of the results of the project, recycling in concrete road construction is to be facilitated and thus the development process of a cycle-oriented use of raw materials in road construction is to be advanced. Objectification through an evaluation based on relevant parameters is an important key function in order to increase the acceptance of recycled building materials in the construction industry and to reduce prevailing uncertainties.

Investigation of a novel grinding process for the production of fully defined surfaces (08.0267)
The focus of the research project is on the further development of the grinding technology for the production of performance -oriented surfaces. The aim is to use an optimized cutting shaft configuration that produces fully defined surfaces with homogeneous ridge heights. The project further focuses on the influence of the cutting pattern on the relevant surface properties (including skid resistance, drainage, acoustics) and the reliable achievement of improved acoustic properties with high durability, taking into account the stresses that occur (traffic, climate). The installation of a test track will enable the combined investigation of the grinding textures on the one hand and the large-scale application of the optimized cutting shaft equipment on the other.

Acoustic optimization of concrete road surfaces by surface texturing (08.0222)
The research project aims to create the metrological prerequisites for the geometrical recording and evaluation of the temporal development of longitudinal surface textures in-situ and in the laboratory. Thus, the project aims at developing, testing and applying a measuring method based on stripe light projection for the defined, repeatable, spatial acquisition of textured concrete surfaces in situ and in the laboratory. This also includes the development, testing and application of suitable evaluation routines for the qualitative and quantitative description of textures and texture changes taking into account the segmented hardened concrete components. These form the basis for the objective analysis of the temporal development of changes in the surface texture as a function of the external effects of climate and traffic. In addition, a multi-stage procedure is to be used to examine the influence of the concrete recipe on the durability of the concrete depending on the texture. The influence of the concrete composition as a function of the texture on the grip, the drainage capacity, the noise properties in the context of the wear susceptibility will be systematically analysed.

Influence of concrete composition of road concretes on splitting tensile strength under consideration of sufficient durability (08.0255)
Within the framework of the project, the influence of the concrete composition - especially on special concrete formulations developed for grinding technology - on the splitting tensile strength determined on cylinder disks is to be determined. Here, in comparison to current standard formulations, the exact relationships between the individual starting materials, the resulting concrete compositions and the splitting tensile strength are to be examined and evaluated in detail. In order to enable a targeted design of such concretes and to be able to take targeted countermeasures if the requirements are not met, the effects of all relevant concrete technology parameters must also be determined. At the same time, the durability of the concrete is to be discussed on the basis of a proven splitting tensile strength. The results are to be used to develop current and, in particular, new concrete formulations for road pavements with a view to achieving the required splitting tensile strength. In addition, it should be possible to make well-founded statements on the relationships between the splitting tensile strength and the concrete properties or characteristic values relevant to durability and to define possible requirement values.

HESTER (3715008)
Pavements are exposed to the effects of traffic as well as climate. Since both of these variables are subject to varying degrees of change, only limited recourse can be made to existing data based on past experience when assessing the durability of the pavements. There has been a fivefold increase in traffic load in the past 30 years, for example, and the heavy goods traffic volume is expected to double during the next 30 years. The effects of climate change can likewise be clearly seen already. Upgrade systems that can be used in a relatively short period of time are needed to maintain road availability, and a priority here is the durability of the maintenance measures conducted. The project’s objective is to further develop the precast concrete method for road surfaces in order to boost the durability of pavements, reduce construction times in situ, improve efficiency and make careful use of resources both for new builds and maintenance. Application fields are opened up primarily in the municipal sector – notably bus lay-bys and bus stop areas as well as roundabouts and busy intersections in urban and non-urban areas that are subject to considerable stress from braking and acceleration processes.

Analysis of the structure-related solubility behaviour of potential ASR sensitive aggregates (06.0108)
Developments in recent years as well as ongoing research, for example in the areas of continuously reinforced concrete road surfaces and/or fibre concrete, show that concrete road surfaces still have considerable potential in terms of extending load-oriented service life. One problem that has not been satisfactorily solved in recent decades is the damaging alkali-silica reaction (ASR) in the area of concrete construction. The objective of the research project is to investigate, analyse and describe the physical and chemical processes as well as the connection between the structure of grit in the surface area and its solubility in an alkaline environment for selected aggregates with differing degrees of alkali sensitivity. This is specifically designed to establish and extend the knowledge and understanding about the reaction processes on the surface of aggregates. The collected findings should in future contribute to the ability to conduct a fast and reliable assessment of aggregates with respect to their behaviour in an alkaline environment, in order then to be able to estimate their resistance to ASR.

Use of open-pored concrete in road construction (3712002)
The objective of the project is to develop a concrete road surface whose top layer is produced from open-pored concrete. Unlike the currently practised two-layer construction method "fresh-on-fresh" in this method the top concrete layer is applied on a hardened surface in a first step. Another objective is optimization of the construction method, so that permanent noise reduction hand in hand with high drainage capability and good skid resistance can be ensured. The development of permanent noise-reduced open-pored concrete road surfaces is intended to establish an alternative to open-pored surfaces in asphalt construction method in order to provide road construction administrations with a scope for organising work in road construction design in spite of increasing requirements for noise reduction.