Date of Award
Master of Science
Civil, Construction, and Environmental Engineering
Civil Eng ineering ( Geotechnical Engineering)
Jeramy C Ashlock
Granular surface roads in rural Iowa were frequently subjected to freeze-thaw cycle. Which resulting road damage such as frost heave, frost boils, thaw weakening, rutting and potholes. These damages increase the maintenance costs, bring public safety issues, and cause inconveniences to the traffic. Several stabilization methods have been tested by pervious study Phase II Iowa Highway Research Board Project TR-664 “Low-Cost Rural Surface Alternatives: Demonstration Project” for improving the resistance towards freeze-thaw cycle damage, and this project focused on investigating additional soil stabilization methods for preventing Iowa's rural roads from freeze-thaw cycle damage.31 test sections in four different Iowa counties were selected in fall 2018 for this project, and six mechanical methods and five chemical stabilization methods were implemented and examined in all these sections. To analysis the damage caused by freeze-thaw cycles, field and laboratory tests were continually performed for the next two years, including winter 2018, spring 2019, winter 2019 and spring 2020. The field tests include road surface survey, falling weight deflectometer (FWD), light weight deflectometer (LWD), dynamic cone penetrometer (DCP), nuclear gauge density and sample collection. The laboratory tests include sieve analysis, Atterberg limit tests, shear strength tests and durability tests. Along with two years of study, shear strength and composite elastic modulus were significantly improved by combining cement treatment methods and the optimized gradation with clay slurry method compare to other Test Sections. The steel slag sections show good resistance performance at beginning but cannot keep it well at the second year. Except the cement treatment method, all the chemical stabilized methods are worse than control sections. The ground tire rubber section works awful so the research team eliminate this section at beginning. Accordance with the cost results, the 12” subgrade cement-treatment method are too expensive on hauling and equipment renting. The steel slag sections have relatively high cost on hauling since the material resource are distance away from construction site. The cost of RAP asphalt material is also going up these two years. Above all, the most cost-effective method was found to be the 4" surface cement-treatment method combined and the optimized gradation with clay slurry (OGCS) method.
Xue, Ziqiang, "Contsruction and performance of chemically and mechanically stabilized granular road test sections" (2020). Graduate Theses and Dissertations. 18430.