Ground granulated blast…

Ground granulated blast furnace slag (slag) or fly ash or a combination of the two materials and shall be restricted to the following proportions by mass of the total cementing material:
a) Slag up to 25%.
b) Fly ash up to 10%, except for silica fume overlays and HPC where up to 25% is permitted.
c) A mixture of slag and fly ash up to 25%, except the amount of fly ash shall not exceed 10% by mass of the total cementing materials, in concrete other than silica fume overlays and HPC

Restricting the proportions of slag and fly ash in the concrete mix can compromise the material's long-term durability, elevate the heat of hydration, and reduce sustainability—contradicting MTO's greenhouse gas (GHG) reduction initiative. Additionally, it restricts the ready-mix producer from optimizing their mix design to deliver the most suitable mix for the intended application. Overall, this requirement significantly affects concrete performance in Ontario.

1350.07.04.02 Discharge Time
When concrete is transported to the site by means of agitating or mixing equipment, discharge of the concrete into the work shall be completed within 1.5 hours after introduction of the mixing water to the cement and aggregates, except when the air temperature exceeds 28 °C and the concrete temperature exceeds 25 °C, the concrete shall be discharged into the work within 1 hour after the introduction of the mixing water.

This requirement should be aligned with CSA A23.1, allowing for 2 hours and 1.5 hours respectively. With advanced admixtures now available, this restriction unnecessarily compromises concrete performance and results in added waste and costs from rejected loads.

1350.05.04.02 Hardened Concrete Requirements

The MTO remains the only owner in Canada that does not conform to CSA A23.1 exposure classes. Specifying 30 MPa for bridges in contract documents is not only imprudent but also negligent, and the concrete industry in Ontario strongly disagrees with the MTO’s approach to concrete specification. Although the MTO references CSA A23.1, it has no intention of adhering to its requirements, resulting in concrete that is not only less sustainable but also significantly more costly for taxpayers.