Application and analysis of preventive maintenance techniques: Chip seal and Otta seal

Gushgari, Sharif
Major Professor
Ashley F. Buss
Committee Member
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Civil, Construction, and Environmental Engineering

Since their first application, preventive maintenance treatments on pavement surfaces have cost millions of dollars to provide safe and accessible roadways to benefit the public. Chip seal and Otta seal treatments have been utilized since the early 1900s and mid-1960s, respectively. Chip seal has evolved over the years, from empirical approaches to rational design approaches, to enable practitioners to serve public needs on roadways. Otta seal was first applied in Norway in 1953. Utilization of chip seal and Otta seal treatments continued to advance based on the need to maintain older pavement surfaces accessible across the world and to sustain new roadways as the population worldwide continue to grow and expand. It is projected the needs of preventive roadway maintenance techniques will increase considerably because the world economy has shrunk by 5.2% in 2020 during the COVID-19 pandemic. Preventive maintenance techniques such as chip seal and Otta seal are alternatives to major rehabilitation treatments which can be applied to extend the service life of roadways. The first paper in this dissertation research studied Otta seal project implemented and evaluated on a total of 6.4 km (3.97 mi) of roadway. Otta seal was applied for the first time ever in Cherokee County, IA in collaboration with the Iowa Department of Transportation. Otta seal evaluation techniques involved visual inspections, international roughness index, light weight deflectometer, dustometer and loose aggregate tests at different construction and service periods. These evaluation methods performed on Otta seal surfaces in Iowa revealed that Otta seal surfaces can provide an economical and durable alternative bituminous surface treatment for low-volume roads to ensure safe roadways for public usage. In the second paper, a chip seal case study focused on investigation of adapting state-level pavement preservation specifications to meet local agency needs in Ohio was conducted. The case study revealed that chip seal is one of the most common preventive maintenance tools used by roadways engineers to extend the service life of pavement, and can be maximized if chip seal is applied under optimal pavement and weather conditions. Another major finding is that updating specifications to meet local agencies needs will allow local agencies to utilize chip seal under controlled standards. The third paper studied chip seal test sections that were constructed in Oregon in 2014, 2015, and 2019 in collaboration with Oregon DOT to investigate and research the possibility of adopting the New Zealand chip seal performance-based specification for chip seal roadways in Oregon. Performance-based specification was investigated in this study by utilizing the sand circle test which is capable of determining the macrotexture of chip seal surfaces. The Oregon test sections database of MTD for five years enabled for further investigation to generate prediction models probabilistically and deterministically. The implementation of performance-based specifications associated with chip seal is becoming an interest of roads agencies to provide roadways with measurable performance indicators and to enable contractors’ creativity for incentives and advantages.