Field Evaluation of Using Slag as Aggregates for Otta Seal Surfacing

Abstract

Otta seal surfacing technology is an application of thin bituminous surface treatment (BST) with graded aggregates and emulsified or cutback asphalt binder. Due to the employment of locally available aggregates and ordinary construction equipment, it dramatically reduces road resurfacing costs compared to traditional BSTs such as chip seal. In recent years, Otta seal has been tried for low-volume roads in a few states in the USA. However, most of the Otta seals adopted crushed limestone or river gravels, and recycled materials, such as slag, have never been investigated. To evaluate the performance of using slag for Otta seal, two gravel roads in Louisa County, Iowa were selected to be resurfaced. Slag collected from a steel mill was applied instead of regular road aggregates. To monitor the performance, dust caused by passing traffic was measured, and elastic modulus, skid resistance, and international roughness index (IRI) were tested before and after the Otta seal construction. The results indicate that slag-based Otta seal reduced the surface dust dramatically and maintained an acceptable skid resistance. However, it also presented a high IRI values due to the poor compaction and unsatisfied slag gradation. In addition, the newly constructed surface exhibited excellent appearance, and no distress was found after eight-month service. In summary, the findings from this study showed that recycling slag as an alternative aggregate for Otta seal is quite feasible.