INVESTIGATION OF PORTLAND CEMENT CONCRETE EXPOSED TO AUTOMATED DEICING SOLUTION APPLICATIONS ON COLORADO’S BRIDGE DECKS

摘要

The Colorado Department of Transportation (CDOT) has identified potential performanceproblems in some portland cement concrete (PCC) bridge decks and approach slabs in the formof pattern surface cracking, spalling, and joint/crack deterioration, which are suspected to bematerials-related distress (MRD). External factors, such as the use of deicing/anti-icingchemicals, have the potential to initiate and increase the rate and magnitude of deterioration dueto MRD, thereby shortening the life of the structure.This paper details the results of a study conducted to investigate whether the applicationof highly concentrated deicer solutions through fixed automated spray technology (FAST)automated bridge deck deicing/anti-icing systems is disproportionately contributing to thedeterioration of PCC bridge decks and adjacent concrete approach slabs in Colorado and whethermitigation strategies being employed by CDOT are addressing the problem. The approach tothis investigation involved the use of visual inspection techniques, materials sampling, and theevaluation of the sampled concrete using petrographic methods.In the bridges studied, the concrete evaluated appears to be sufficiently resistant todamage from the intrusion of deicer chemicals, though where full-depth cracking was present,obvious signs of the movement of moisture and deicers through the deck were observed. Inaddition, some initial signs of possible chemical deicer attack were noted, and continuedexposure to highly concentrated deicers may contribute to long-term durability concerns.However, the use of polymer-modified asphalt/fabric membranes in conjunction with a hot mixasphalt (HMA) overlay appears to be very effective in preventing the ingress of chlorides intothe underlying concrete deck.