Laserfiche WebLink
Chapter 3. Conclusions and Recommendations <br />Conclusions <br />The stripping of the HMA pavement after application of chip seal is caused by areas of high air <br />voids or low density. The lack of proper compaction allows water to permeate into the HMA <br />and cause pavement to strip. This also occurs in HMA that are not prone to stripping. A cause <br />for lack of uniform density is the use of the ordinary compaction method. For ordinary <br />compaction to work, inspections must ensure all areas of the pavement receive proper <br />compaction efforts at the correct temperature for the mat. <br />Recommendations <br />It is recommended that agencies use specified density methods to ensure proper uniform <br />compaction of the HMA paving. An observation by a city's personnel was when the city <br />switched to specified density the same Contractor brought two 20- to 25-ton steel rollers and a <br />20- to 25-ton pneumatic roller instead of one 6- to 8-ton steel roller they used in the past when <br />ordinary compaction was specified. The cost of the HMA was the same per ton. Areas that need <br />more research into are what effects recycled asphalt (RAP) now used in wear course have on <br />stripping. <br />There are currently three options for existing streets with low density and high air voids <br />variability. These options are as follows: <br />1. Do nothing and allow the street to fail prematurely. <br />2. Chip seal earlier in pavement life to try to keep pavement structure as dry as possible to <br />limit moisture damage. From the surveys in Task 1, it appears that chip sealing the <br />pavement within the first 1-4 years of life helped to limit the stripping issues. <br />3. Fog seal pavement with a CSS-lh diluted to one part water and one part emulsion. <br />6 <br />