ROADS: Constructions under increasing loads

Road and Railway EngineeringCivil Engineering and Geoscience

Durable and Sustainable Road Constructions for Developing Countries

This paper discusses the possibilities to build durable and sustainable pavement structures in developing countries. Attention will be paid to geometric design aspects which have a significant effect on pavement life. Following this attention will be paid to the importance of controlling wheel loads rather than axle loads. Also the importance of controlling tire pressures is discussed. The paper continues with a discussion on the importance of proper construction. Finally it is shown that re-use of construction demolition waste and hot recycling is very well possible and results in good quality materials which can be used to build durable and sustainable pavement structures.Structural EngineeringCivil Engineering and Geoscience

Structural performance and design of flexible road constructions and asphalt concrete overlays

Summary in DutchCivil Engineering and GeosciencesCivil Engineering and Geoscience

Estimation of fatigue characteristics of asphaltic mixes using simple tests

A simplified procedure for estimation of fatigue characteristics of asphaltic mixes is presented. The procedure requires the determination of the so-called master curve (Le. the relationship between the mix stiffness, the loading time and the temperature), the asphalt properties and the mix composition. It is shown that the master curve does not only give information about the variation of the mix stiffness, the loading time and the temperature, but also on the fatigue behaviour of asphaltic mixes. This information can reliably be obtained from rather simple tests, which can be performed in any road-engineering laboratory. Procedures of the determination of the fatigue characteristics of asphaltic mixes from simple tests are of special interest in mix design procedures where the quality of various mixes with respect to fatigue and crack resistance has to be evaluated. It is obvious that such a procedure is also extremely attractive for specification and pavement evaluation purposes. An insight is provided as to how the fatigue parameters for an asphaltic mix can be estimated using the Wohler approach.Laboratory for Road and Railroad ResearchCivil Engineering and Geoscience

Application of aging methods to estimate long term performance of secondary materials for road construction

Long term performance of secondary materials is becoming a challenging aspect in road construction since due to their benefits they are being used on a large scale, but on the other hand their future behaviors are difficult to estimate. In this study, aging is proposed as a means of exploring the long-term mechanical and physical performance of secondary materials. A Blast Furnace Slag (BFS) mixture which is routinely used in the Netherlands in road (sub-) base construction was selected as a reference material. The A32 motorway in the Netherlands was used as a source of field aged granulated BFS materials. The base layer of this motorway, suddenly experienced serious failure. Different failure mechanisms have been hypothesized. In order to estimate future behavior of secondary materials and to prevent similar problems to occur an aging protocol was suggested to detect at an early stage potential poor material performance. Two types of aging approaches were chosen and applied to the field aged and fresh materials being steam aging and cyclic freezing and thawing. Both aging treatments have affected mechanical and chemical characteristics. The study of response variables showed there is a linkage between compressive strength, expansion, micro cracking and amount and type of binder.Structural EngineeringCivil Engineering and Geoscience

The crack growth mechanism in asphaltic mixes

The crack growth mechanism in asphalt concrete (Ac) mixes is studied. In cyclic tests on several asphaltic mixes crack growth is measured, both with crack foils and with cOD-gauges. It is found that crack growth in asphaltic mixes is described by three processes which are parallel in time: cohesive crack growth in the mortar, adhesive crack growth between the mortar and the aggregates and a crack stoppers process. Differences in overall crack growth in asphalt concrete are due to differences in the contributions of each individual process to the overall process.Road and RailroadCivil Engineering and Geoscience

Characterization of Blast Furnace Slag to be used as Road Base Material

In congested areas around the world, traffic has significantly grown beyond expectation both in terms of volume and weight. Any hinder to the traffic causes severe delays resulting not only in economic loss but also in extra pollution of the environment. Therefore, maintenance works are desired to be reduced as much as possible. Application of self-cementing materials such as Blast Furnace Slag (BFS) for base courses is one of the methods to reduce the need for maintenance, since such base courses can provide a significant increase of the stiffness and the strength of the pavement structure. However, this type of stabilization appears to be associated with undesired deformations and distresses such as heaves formation and cracking that occurred, e.g. on the A32 motorway in the Netherlands. Different failure mechanisms have been hypothesized. This means, the use of BFS in a road (sub-)base layer requires a good knowledge of its characteristics. This paper presents data on the chemical and mineralogical characteristics of fresh and field aged BFS materials from a case study in the Netherlands. Furthermore a microstructural study was done on samples which have experienced freezing and thawing cycles.Structural EngineeringCivil Engineering and Geoscience

The Prediction of Fatigue Life Based on Four Point Bending Test

To be able to devise optimum strategies for maintenance and rehabilitation, it is essential to formulate an accurate prediction of pavement life and its maintenance needs. One of the pavement life prediction methods is based on the pavement's capability to sustain fatigue. If it were possible to have a prediction that closely represent what is observed, we will come up with right decisions for pavement maintenance. The aim of this paper is to predict the fatigue life of gravel asphalt concrete based on four point bending tests and compare it with observation of two accelerated pavement test sections. New gravel asphalt concrete (GAC) specimens were made based on the original GAC mix design. The Four Point Bending Tests were carried out in the same frequency range as loading frequency (loading time) applied in the accelerated pavement test. The result shows that the observed fatigue life is higher than the predicted.Structural EngineeringCivil Engineering and Geoscience

Investigation of the resilient behavior of granular base materials with simple test apparatus

In many developing countries, where resources are at premium, thin asphalt layers or chip seals are widely used to provide a durable all weather pavement surfacing. In such pavements the role of granular layers is very important in the general performance of the structure. Pavement designs in these countries are empirical in nature and rely on simple input parameters like California Bearing Ratio (CBR) values. Although widely applicable the traditional CBR test does not provide the mechanical properties such as resilient and permanent deformation characteristics of granular road materials. This paper documents the characterization technique developed to determine the mechanical behavior of granular (sub-) base materials based on CBR test using repeated load cycles. The confining pressure developed in the complex CBR stress state is estimated using strain gauges. Finite Element analysis has been attempted to model the repeated load CBR (RL-CBR) and derive an equivalent resilient modulus. Furthermore, a large scale cyclic load triaxial test was carried out on coarse unbound granular materials (UGMs) to validate the result of the RL-CBR. The RL-CBR test reasonably estimates the resilient modulus of UGMs which can be used as an input in mechanistic pavement design analysis in the absence of triaxial testing facilitiesStructural EngineeringCivil Engineering and Geoscience