No description available.

Concrete pavement systems have great capacity to provide long service lives; however, if the subbase layer is improperly designed or mismanaged, service life would be diminished significantly since the subbase layer performs many important roles in a concrete pavement system. The erosion of material beneath a concrete slab is an important performance-related factor that if applied to the selection of base materials can enhance the overall design process for concrete pavement systems. However, erosion of the subbase has not been included explicitly in analysis and design procedures since there is not a well accepted laboratory test and related erosion model suitable for design. Previous erosion test methods and erosion models are evaluated in terms of their utility to characterize subbase materials for erosion resistance. With this information, a new test configuration was devised that uses a Hamburg wheel-tracking device for evaluating erodibility with respect to the degree of stabilization and base type. Test devices, procedures, and results are explained and summarized for application in mechanistic design processes. A proposed erosion model is calibrated by comparing erosion to lab test results and LTPP field performance data. Subbase design guidelines are provided with a decision flowchart and a design assistant spread sheet for the economical and sustainable design of concrete pavement subbase layers by considering many design factors that affect the performance of the subbase.

Centrifugal separation is a crucial piece of technology, used in a wide range of industries. In cases where solid particles are included in the working medium, erosive wear of componentsinside a centrifugal separator is one of the reasons limiting its service life. In the present work, erosion of some candidate materials of metals, hard metals and polymers were tested to represent the erosive conditions inside a centrifugal separator, and to study the erosion behavior between different material groups. A literature study was conducted to give an overview of the field of erosion, and to evaluate which erosion parameters to consider for testing. A centrifugal erosion test rig was used for the testing, using natural sand, sieved to a size interval of 500 to 700 µm, as erodent, at both 90° and 30° impact angle. Every material was tested at 100 m/s impact velocity, while only metals and polymers were tested at 70 m/s. The erosion rates, volumes of material removed per mass of impinging erodent, were measured and used to rank the candidate materials within each respective material group. Surface analysis of the eroded surfaces were conducted, using SEM, to determine the mechanism of material removal. Relation between erosion resistance, erosion mechanism and material property were investigated.