Establishment of MTO RM ASR CA6 as a Replacement for Spratt No. 3

This paper presents the results of the Ontario Ministry of Transportation’s (MTO’s) work to validate a new alkali-silica reactive (ASR) reference material (RM) as a replacement for the internationally recognized Spratt No. 3. Availability of Spratt No. 3 has been restricted in recent years due to the limited quantities remaining, and the need for MTO to conserve remaining resources for control and calibration of AAR test methods until a comparable replacement material could be established and validated. Prospecting for a new MTO ASR RM source in the same geological formation as, and with comparable characteristics to Spratt No. 3 was undertaken by MTO between 2018 and 2020. Screening of prospective sources included sampling and testing, i.e., accelerated mortar bar testing (AMBT) to assess the level of reactivity, and insoluble residue (IR) testing to assess the general composition. Once exploration identified a suitable candidate source, further investigations including geological examination, sampling and testing were conducted to pinpoint the most highly ASR areas and strata within the quarry in preparation for aggregate production. MTO RM ASR CA6 was produced (drilled, blasted, crushed, transported) and placed in stockpile in MTO’s Aggregate Storage Building in September 2020. MTO RM ASR CA6 has been included in several Soil and Aggregate Proficiency Sample Testing Programs (SASTP) conducted by the Soils and Aggregates Section of the Engineering Materials Office since 2021. Data generated by the SASTP has been utilized to obtain material properties and to validate and establish MTO RM ASR CA6.

Preliminary SASTP results indicate that MTO RM ASR CA6 gives similar or higher expansions in both the 14-day AMBT and 1-year CPT as compared with Spratt No. 3. Additional geochemical and petrographic data further confirm the comparable nature of MTO RM ASR CA6 and the Spratt aggregate.