Alkali-silica reactivity in the state of Montana

Abstract

While ASR has been documented as an issue in many states, little work has been conducted to determine the presence/potential of ASR in Montana. Thus, the primary objective of this research was to evaluate the potential for deleterious ASR in the state of Montana. In connection with this goal, a literature review was conducted to summarize the ASR practices used by neighboring state departments of transportation, as well as several federal agencies. Three potential cases of ASR damage in the state were identified and investigated using the Los Alamos Staining Method and ASTM C856. These sites included two at the Billings Logan International Airport and one at the Willow Creek Dam Spillway. Additionally, the reactivity eight aggregates, selected from various locations around the state, was tested in accordance with ASTM C1260 (Accelerated Mortar Bar Test), AASHTO T380 (Miniature Concrete Prism Tests). The literature review concluded that Canada and all other regional states explored, with the exception of North Dakota, directly addressed ASR in their material specifications, to varying degrees. The FHWA defers to individual states to determine ASR practices, while the FAA has fairly stringent specifications. The hardened concrete analyses conducted for the two Billings Logan International Airport Los sites indicated the presence of ASR in both locations; more specifically, the damage was classified as severe/Type V according to two separate criteria. The results of the Willow Creek Dam Spillway petrographic examination indicated the severity of the ASR distress observed in the spillway varied based on location, with advanced ASR detected in the ogee. This aspect demonstrated that cases of ASR in Montana do exist, and that the infrastructure in the state is susceptible to this type of failure mechanism. The results of the aggregate testing indicated that all the fine aggregates were reactive and very highly reactive according to ASTM C1260 and AASHTO T380, respectively. Two of the four coarse aggregates were innocuous according to ASTM C1260, while all of the coarse aggregates were reactive, to varying degrees, according to AASHTO T380. It was concluded that Montana's aggregates are susceptible to ASR.