Surfaces and Guideways

Topics: Concrete, Rail tracks, Portland cement Pages: 6 (2036 words) Published: January 12, 2013
Surfaces and Guideways Introduction Basic Components Structural Design of Pavements Portland Cement Concrete Design Asphalt Concrete Pavement Design THE END Thank you Surface - the term surface refers to Roadway pavement which includes Portland Cement concrete, treated soil (gravel or other aggregate materials) and Asphalt concrete Guideway - A track along which Automated Transit Vehicles are guided. Guideway include monorails, concrete guideway for rubber tired vehicles and conventional duo-rail steel-on-steel railroad track Surface Course - also known as the pavement. It is the material laid over the Base Course consisting of Asphalt Concrete or Portland Cement Concrete. Base Course - is the material laid on top of the sub grade consisting of crushed stone or gravel.They may be stabilized by means of lime, Portland Cement, or Asphalt Sub-grade or Sub-base - is the earth beneath the road, properly arranged and graded, compacted and stabilized. It is defined as the "supporting structure on which the pavement surface and its special under-courses rest" The design of pavements involves determination of the types and thickness of the various layers of material making up the pavement. The goal is to specify the most economical pavement which will perform satisfactorily over a designed life so that comparisons between the two require Total Life Cycle Cost Analysis The most common design for Portland cement concrete pavement is the AASHTO rigid pavement design method. Like AASHTO flexible pavement procedure, this method relates to soil conditions, traffic characteristics and pavement design characteristics to a performance index value expected at the end of the pavement life. Highway Pavements Components Life Cycle Analysis for Concrete Life Cycle Cost Analysis for Asphalt Result: Total Life Cycle of Concrete pavement VS Asphalt Concrete Design Considerations Portland Cement Vs Asphalt Concrete Portland Cement Concrete Portland Cement concrete pavement are considered to be rigid so that the slab rebounds after the deflections due to the load. Failure mechanism is to be fatigue caused by certain number of repetitions of a significant load Asphalt Concrete is considered to be flexible and the failure mechanism is assumed to be plastic deformation due to the cumulative load over the life of the pavement Asphalt Concrete Pumping - is the ejection of water and sub-grade soil through the joints and cracks along the edges of the concrete pavement. Fine materials in a saturated base form a slurry with the water in the base. This is what usually happens on a faulty design method: Asphalt Concrete pavements are often used on lightly traveled roadways. It is not always necessary to use complicated design methods for them; rather design may be by precedent with standard thickness being specified for each of the pavement layers according to the type of the roadway involved (such as local street, collector, and arterial) Design Considerations Design Considerations SN is an abstract number (SN) that represents the structural strength required for a pavement to perform in accordance with the design criteria. Gravel Equivalent Thickness Pavement Maintenance and Rehabilitation Pavements are subject to varying degrees of distress short of outright failure that reduces their serviceability. Asphalt Concrete pavements are subject to a variety of types of pavements distress or failure. these include: Transverse Cracking - Cracks approximately at right angle to the pavement center line. These may be caused by hardness and shrinkage of asphalt or differential thermal stresses of asphalt concrete or may be reflection cracking. Block Cracking - Cracks forming large interconnected polygon usually with sharp corners or angles. These cracks are generated by hardening or shrinking e.g. asphalt or reflection cracking for underlying layers such as cement treated base. Alligator Cracking - A series of interconnecting or interlaced cracks caused by fatigue of the...
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