This is a comment on the…

This is a comment on the Prestressed Concrete Girder Guidelines (August11 2023).pdf document but more specifically on OPSS.PROV 909 clause 909.07.12.01.

Specifically, the clause in question is: "Moist curing of exposed surfaces shall be applied within 2 to 4 m of concrete placement, except for girders produced in an indoor precast concrete plant and not containing silica fume; for such girders, exposed surfaces may be covered with moisture vapour barrier between concrete placement and concrete finishing, for the shortest practical time period and in no cases exceeding 40 minutes."

First, it is unclear if 2 to 4 m means 2 to 4 minutes or 2 to 4 metres. The unit symbol needs to be removed and the full word used to make this sentence clear.

Second, this is too restrictive to be practical. OPSS.MUNI 909 allows a cumulative total exposure of 3 hours during the moist curing period. The provincial requirement to apply moist curing within 2 to 4 minutes is not reasonable. If this could be relaxed to applying moist curing within 15 to 20 minutes of concrete placement then it would become possible for more precast fabricators to bid provincial projects and allow for competition in the precast concrete girder market. Right now there is only one fabricator in Ontario who can meet this requirement. Most other fabricators will bid municipal projects but refuse to bid provincial ones solely because of this clause. This is driving the cost of precast girders up and pushing the industry to steel girders. Which is the reason for this comment, since if you don't relax the requirement of OPSS.PROV 909.07.12.01 then there is no need for the Prestressed Concrete Girder Guidelines document.