Better Roads Digital Magazine
Issue link: https://read.dmtmag.com/i/86539
BaseBreakthroughs A HighwayContractor By John Latta quick look at some recent research into sub-bases presented at the American Society of Civil Engineers (ASCE) GeoCongress 2012: State of the Art and Practice in Geotechnical Engineering, held this spring in California, suggests that sub-base options are increasing rapidly. The full ASCE papers (below are ab- stracts) are available through the society's website, www.asce.org Reusing Glass The recycling industry continues to grow as a means of utilizing waste materials in today's world and as such more markets must be urgent- ly established for recycled products. Currently in the state of Victoria, Australia, 186,000 tonnes of recycled glass are stockpiled annually and these stockpiles are growing. However, there is little known reuse application for recycled glass in pavement sub-base applications due to lim- ited knowledge of its geotechnical properties. The reuse of recycled glass in road pavement applications will provide the opportunity not only to get rid of the waste glass stockpiled and minimize the use of virgin materials in pavement applications but also to minimize the valuable land being used for stockpiles. This paper pres- ents a preliminary laboratory evaluation of select geotechnical properties of recycled glass when used in blends of up to 50 percent with recycled crushed concrete in pavement sub base applica- tions. Laboratory tests discussed in this paper in- clude modifi ed compaction, Los Angeles abrasion loss, consolidated drained triaxial compression test and California Bearing Ratio (CBR) test. The fi ndings of this laboratory evaluation indicate that potentially up to 30 percent recycled crushed glass of particle size less than 4.75 mm could be safely added to Class 3 recycled crushed concrete in pavement sub base applications. Paper is entitled: Potential Use of Recycled Crushed Concrete-Recycled Crushed Glass Blends in Pavement Subbase Applications Triangle Power A fi eld study was performed to document the benefi t of a punched and drawn polypropylene triaxial geogrid. The triaxial geogrids have triangular apertures and increased rib thickness as compared to many geogrids with square apertures. These fundamental changes to the geogrid struc- ture, coupled with high junction effi ciency, gives greatly improved aggregate confi nement and interaction, leading to improved structural performance of the mechanically-stabi- lized layer (MSL). The project consisted of the widening of La Media Road as part of the Highway 905 improvements. La Media Road and Highway 905 typically experience heavy truck traffi c loads from the Mexico/U.S. border crossing. The subgrade material beneath La Media Road is comprised of clayey sand and clayey sand with gravel. Additionally, cobbles ranging up to about 8 inches in diameter were ob- served on the surface of the subgrade. R-Values of 21 and 24 were determined for the subgrade material. Laboratory testing included grain size analysis, Atterberg limits, maxi- mum density, optimum moisture content and R-Value tests. The fi eld-testing consisted of 5-inchdiameter plate load tests on the subgrade and at various levels of the pavement cross- section. Results of plate load testing indicate that the triaxial geogrid increased the modulus of the mechanically stabi- lized section relative to the conventional unbound aggregate pavement section. The measured improvement of the MSL sections ranged between 27-percent and 52-percent greater than the 30-percent thicker unbound aggregate conventional design section. Paper is entitled: Performance Verifi cation of a Geogrid Mechanically Stabilized Layer Flexible Pavement Design as Part of the La Media Road Widening Project Researchers dig into sub-bases Better Roads October 2012 7