Using electrical resistance to evaluate the chip seal curing process

Chip seals are among the most cost-effective surface treatments available for pavement preventive maintenance. However, frequent issues associated with asphalt emulsion early mechanical strength development, resulting in premature surface treatment failure, have led to the need to improve the characterisation of the chip seal curing process. As such, the use of an electrical resistance measurement has been studied to develop a sound construction methodology that prevents common failures that occur soon after construction. This paper presents a novel approach, based on electrical resistance measurements, to determine when a chip seal has developed enough binder adhesive strength to bond to the existing pavement while keeping the aggregate chips in place. The electrical resistance measurements provide a rapid, non-destructive indication of the amount of curing that has occurred. By implementing this methodology the user can determine when a chip seal has gained sufficient mechanical strength to allow for brooming or opening to unrestricted traffic without an undue loss of cover aggregate. Laboratory and full-scale field trials were conducted using a variety of materials. The electrical properties of the fresh seal coats were quantified by employing a handheld electrical device with a two-point probe resistance measurement. The experimental results suggest that chip seal systems have gained significant mechanical strength when the initial electrical resistance measurement increases by a factor of 10. As a result, this study establishes that electrical resistance measurements can be used to determine when a fresh chip seal has sufficiently cured to withstand the shear forces of brooms and uncontrolled traffic. The implementation of the technique could potentially impact chip seal construction quality, as well as service life performance.