Agenda - Council - 02/11/2020 - Laserfiche WebLink

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CHAPTER 1: INTRODUCTION 1.1 BACKGROUND Preventative maintenance ensures that roadways at all agency levels provide a maximum return on investment. Effective maintenance efforts rely on an understanding of pavement loads (environment and traffic) and proper construction and materials. A critical variable that relies on engineer experience and awareness is timing, or when to initiate maintenance on a given roadway. Unfortunately, the timing of maintenance events, such as chip sealing, can be complicated by unforeseen distresses that reduce the life span for a treatment. Identifying the factors that contribute to chip seal, or seal coat, performance has been a pavement engineering research concern for many decades, with studies on surface treatments dating back to 1928 (Gransberg & James, 2005). In addition, recent major studies have attempted to isolate factors (such as materials, design, and construction practices) that contribute to better performing chip seals (Gransberg & James, 2005). These major studies provide sound, general advice on the use of chip sealing as preventative maintenance; however, ultimately chip seal performance is a local issue given that (1) the treatment itself is thin and short-lived, (2) small variations in materials or construction, which are known to vary by source/location, can have large effects on performance, and (3) overall performance can depend heavily on the environment. At the 2014 City Engineers Association of Minnesota, a discussion on asphalt paving mixes included the topic of stripping under chip seals, which was emerging as a major concern for over one-half of city engineers (Garrity, 2014). Stripping is understood to be the loss of asphalt concrete material near the asphalt surface (at the bottom of the chip seal), due to a break -down in the bond between the binder and aggregate in the asphalt. This phenomenon is illustrated in Figure 1 using a sample taken from a Minnesota road during the research. Figure 1b shows how material from the stripped asphalt remains bonded to the chip. 1