Computer Simulation of Low Volume Roads Made from Recycled Materials
— Low volume roads are widely used all over the world. To improve their quality the computer simulation of their behavior is proposed. The FEM model enables to determine stress and displacement conditions in the pavement and/or also in the particular material layers. Different variants of pavement layers, material used, humidity as well as loading conditions can be studied. Among others, the input information about material properties of individual layers made from recycled materials is crucial for obtaining results as exact as possible. For this purpose the cyclic-load triaxial test machine testing of cyclic-load performance of materials is a promising test method. The test is able to simulate the real traffic loading on particular materials taking into account the changes in the horizontal stress conditions produced in particular layers by crossings of vehicles. Also the test specimen can be prepared with different amount of water. Thus modulus of elasticity (Young modulus) of different materials including recycled ones can be measured under the different conditions of horizontal and vertical stresses as well as under the different humidity conditions. Using the proposed testing procedure the modulus of elasticity of recycled materials used in the newly built low volume road is obtained under different stress and humidity conditions set to standard, dry and fully saturated level. Obtained values of modulus of elasticity are used in FEA.
Performance-based specifications for pavements
Pavement represent a very substantial portion of the public's investment in infrastructure. It is essential that this investment be preserved through cost-effective planning, design, and maintenance. One way of achieving this is through the use of long-term performance-based specifications. This paper describes the current practice for pavement specification. For the most part, these specifications are "recipe" orientated. Very specific requirements are set for procedures, such as compaction, or as constructed properties such as density. With the proposed system, the contractor would be required to warranty the actural performance of the pavement over an extended term. The paper describes the overall scope of the system, its key elements and advantages, and the major risk factors. As well, the measures that can be used to characterize performance and a model for estimating performance are identified. A stochastic formulation of the model is used to present a method of determining the risk to the contractor based on a design example. Finally, the paper explores some of the concerns associated with the implementation of the system and how these concerns might be addressed. (A)
The effect of compaction on the mechanical behaviour of mix granulate base course materials and on pavement performance
This paper describes the influence of compaction on the mechanical behavior of a granular base course material and on the resulting performance of pavements. The results of triaxial tests performed to establish the failure, resilient, and permanent deformation behavior of a specially composed mix granulate compacted to 97%, 100%, 103%, and 105% of maximum Procter density are also presented. Various stress dependent models have been applied to study the observed behavior. By means of finite element calculations in which the modeled behavior has been incorporated, the performance of a 50 mm and a 100 mm asphaltic pavement and of a 80 mm concrete block pavement are analyzed. For these 3 pavements, only the degree of compaction of the base course is used as a design variable. The performance of all of these 'pavements' was analyzed not only on the basis of the conventional design criteria of asphalt and subgrade strain, but also on the basis of stability and permanent deformation of the granular base and sub-base layers.