What type of surface finish should we specify for the top surface of precast stepped grandstand, that will be smooth enough to be able to be kept clean, but not so smooth as to be slippery when wet? The grandstand is in Ontario, open air, and not used in winter, and there is only a crawl space below. Is there any standard top surface finish that is normally specified for this?

I would specifify a broom finish. Slipping should be your major concern. Cleaning is secondary.

May I take it from that, that you have designed/built bleachers with a broom finish?

The top surface of the precast could be formed, depending on details. If either formed or trowelled, an acid wash 1 day after pouring leaves a surface about like sandpaper, & a good sealer will keep it that way. Lousy (well, okay almost impossible) to mop but for an exterior surface it's pretty good if you clean it with a hose. I can't imagine anyone here (I'm in Ontario too) sending you precast with a broomed surface.

Shobroco - thanks for this information. Much appreciated. What acid woould you use. I would be hesitant about hydrochloric acid because it would contaminate the concrete with corrosive chlorides.

Have you ever heard of casting the bleacher slab upside down and then treating the formed surface so that it is not so slippery (perhaps with an acid as you suggest)? I think that is what may have done at the Rogers Centre, but I am not sure.

Must be a lot of precast bleachers around. Anyone know what is usually done?

I think you should leave the concrete finish specification to the architect. Not sure if you want to take the liability for any issue that comes from an accident (slip) in the future.

ajk1...you're not likely to get the precaster to change their methods. Acid washing or grit blasting is easy, just make sure all the acid is consumed or neutralized. Another is to use an epoxy coating with sand broadcast into it before curing. Works well.

I have not seen bleacher seats cast with a rough finish on the walking surface. I've load tested and inspected lots of them and as I recall, the surface texture is an add-on of some sort (even the 3M adhesive grit strips have been used). I've seen many with no surface treatment. Weathering takes care of it.

Sure-Klean 600 used the day after pouring does a good, controlled job of etching a smooth surface. It won't produce noticeable effects in a rough surface.

Rinse well when done.

thanks all. i will contact a precaster and the architect.

This is a link to several non-slip coatings.

BA

BAretired - thanks for the link.

I spoke to the precaster and he says what thye do in their precast arenas is a broom finish.

Our normal procedures are :
(The big question is interior or exterior exposure.)
Usually exterior is broom finished,
and interior is a no line float finish ( not a hard trowel)

In my opinion coatings usually do not hold up for the long term.

The Architect should dictate the finish with guidance from the local precast providers. If they can't / don't want to provide what the Architect wants then a coating is a option.