Evaluation of performance and cost-effectiveness of polymer-modified chip seals

Chip seals provide a durable and functional pavement surface and serve as a highly economical highway maintenance option when constructed properly. Data and literature suggest that chip seal sections constructed with polymer-modified emulsions (PMEs) provide better initial and long-term performance than those with unmodified emulsions and extend the overall service life of pavements. Laboratory test results were used to compare the performance of chip seals constructed with PME (CRS-2L) with those constructed with unmodified emulsion (CRS-2). Both types of emulsion are used to fabricate samples in the laboratory. The overall performance evaluation in the study is based on rutting, bleeding, and aggregate retention performance measured by the third-scale model mobile loading simulator (MMLS3). Results from these MMLS3 tests indicate that, because of improved mechanical properties, the CRS-2L PME enhances chip seal performance to extend the service life of the pavement. Life-cycle cost analysis of two scenarios (one rehabilitation technique that uses chip seal over existing hot-mix asphalt pavement and another that uses chip seal as original construction), indicates that PME becomes a cost-effective solution if the polymer modification can extend the service life of the chip seal from 5 years (typical service life of an unmodified chip seal) to 7 years. The limited laboratory performance test results provide strong evidence that this extension is possible with the CRS-2L PME used in the study.