AMENDMENT TO OPSS 1002, APRIL 2018 - Concrete Aggregates

This posting aims to seek feedback from industry stakeholders on the following key changes:

1. Add air-blast furnace slag to the list of “Unacceptable Material” when tested by LS-616 because it reduces concrete durability and workability. This change is consistent with the current typical practice as air-blast furnace slag has been prohibited in some concrete specifications such as OPSS 909 for prestressed concrete and OPSS 912 for precast concrete culverts with spans greater than 3.0 m.
2. Require that aggregates used in concrete shall come from only the sources on the Structural Concrete Aggregate Sources List or the Concrete Aggregate Sources List for Concrete Base/Pavement Coarse Aggregates (CASL). This change is consistent with the current typical practice and is expected to further facilitate contract administration by waiving the requirements of some lengthy aggregate reactivity tests during production in an MTO contract.
3. Remove the requirement for equivalent cement and alkali content to improve practicality in the evaluation of acceptance of aggregates based on past field performance of a concrete that is at least 15 years old.
4. Change the requirements of total sulphur contents for individual coarse and fine aggregates based on the sulphur data from the submissions received for 2021 CASL. These new requirements were met by all the sulphur data submitted for 2021 CASL.
5. Add a clause for situations where a lot could not be completed due to closure of the construction season or changes in production. This is expected to facilitate contract administration of aggregate quantity used within the year and acceptance of incomplete lots due to such circumstances.
6. Modify the section for acceptance for gradation. This change allows a price adjustment for lots that are subject to a total payment adjustment factor of up to 15%, unless the lots are rejectable for not meeting other requirements of the specification. This change is expected to reduce the risk of directly rejecting material that deviates from the specified grading band by a small fraction. The price adjustment is capped to further reduce the financial risk.
7. Remove CSA test methods from specific sections of the specification and only LS methods are used in QA acceptance. QA and referee labs are practising LS methods for QA acceptance. No CSA but LS methods are included in MTO annual aggregate correlation to maintain the testing proficiency of the industry. Hence it would benefit the industry to use the same LS methods for QC.