3 Geosynthetics Modern civil engineering construction materials Modify/Improve soil/geologic material behaviourDeveloped/Synthesized for specific function or application in constructionMore than 1billion sq m annual use
29 Design Requirements for Asphalt Pavements Before dealing with the individual failure modes, it is appropriate to summarise the design requirements for an asphalt pavement.The surfacing is essentially cosmetic and provides skid resistance and, sometimes, waterproofing.The dense asphaltic materials provide the main structural layer which must have the properties shown.Composite construction can be used in which the lower part of this layer is made from cement treated material. This generates shrinkage cracks which can ‘reflect’ through the asphalt and measures are needed to deal with this problem. Geosynthetics can be applied.The term ‘durability’ has a special meaning in asphalt technology; it refers to resistance to effects of the environment, principally air and water, which can cause ageing and stripping of binder from aggregate respectively.The pavement foundation has to carry construction traffic in the short term (a small number of high stress applications) and provide good support in the long term (a large number of low stress applications).
30 Grid Locations for Asphalt reinforcement This slide shows the preferred locations for geogrid reinforcement of asphalt.One layer at the bottom of the asphalt deals with fatigue cracking, while the additional layer nearer the surface will be effective for rutting.These mechanisms have been demonstrated in research at Nottingham using the Pavement Test Facility.
31 Reflection Cracking Locate near to existing discontinuity Mechanistic design method still evolvingStiff geogrid bestGeotextile can waterproofThis slide sets out the principles for reinforcing an overlay to reduce reflection cracking.
32 Rutting in Overlays Locate where strains are largest; mid-depth Increase in life to critical rut of three timesRequires stiff geogridThis slide sets out the principles for reinforcing asphalt overlays to reduce rutting.
38 Impediments Most of the Geosynthetics are imported. Test Methodology they adopt is from country of origin.Test could be of:-International standards (ISO TC221 Geosynthetics).European Standards (CFN TC Geosynthetics).German Standards DIN textiles norms.British Standards BSAmerican Standards ASTM.Very few Indian Standards.
39 specifications Specifications are from international organizations. AASHO.British Textile Technology Group - BTTG.DGGT- EBGEO, Germany.Geosynthetics Research Institute, USAPresence of large number of test methods & specifications are a matter of concern and confusion.
40 Need for Testing Index Testing-Basic Properties of Products Quality control tests- Rapid testing to assure continuity of equality.Performance testing- Testing of Geosynthetics in contact with soil under standard conditions in the lab to provide better simulation of site conditions. Also in full scale on site.
42 R&D FACILITIES The existing Labs may have excellent facilities but May not necessarily have all relevant facilities for test house.May not maintain ambient temperature and humidity as required by ISO (21± 2°C &65%).May not have necessary Grips for all varieties of Geosynthetics.May not have skilled/Trained Technicians.Not accredited.
43 SUGGESTIONSNeed for establishing national organisation to address the problems.Role:-Functions as a Geosynthetics test house.QC checking at the place of manufacturer.Property assessment of the product for the designer.3rd party quality control testing of product.Testing & evaluation for product certifications.Testing for R&D needs.
44 SUGGESTIONS Render advice to the industry & Govt. Organise short refresher & training programs.Develop laison with all specifying dept. like BIS, IRC & International institutions.Immediate Standardization of specifications, test procedures.Code on the lines of BS 8006.