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Re: Patching small holes in conc. slabs

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Title: Re: Patching small holes in conc. slabs

        Curt,

                If the hole you describe were in the 4" thick flange of one of our double tees, I would:

                1. For about 4" diameter and less, form up underneath the hole and fill it with LA Repair Mortar from ThoRoc (I think it still is considered ThoRoc, though degussa owns it now).

                2. For larger diameters, cut grooves into the top of the slab up to almost 2" deep on both sides of the hole long enough to develop #3s. Lay #3s in the grooves and secure them with Simpson Epoxy-Tie adhesive, then form up underneath the hole and fill it and the top of the grooves with LA Repair Mortar. If the fire which is to be resisted were to heat the bottom of the groove above the temperature that the epoxy would tolerate, I would use just the cementitious repair material to secure the bars, though this would probably require longer development.

                Finally, I would call for the surface to be blended with the existing surface if exposed concrete.

                There are a lot of things that should happen in these processes like cleaning the grooves of dust and applying the mortar to saturated, surface dry concrete, etc.

                Why those products? Because those are the ones that our crews use on a fairly regular basis so we have them in our warehouse and the crews have familiarity with them and are comfortable using them. I take comfort (maybe more than I should) that a familiar product will be applied better than an unfamiliar one. Though there has been a lot of consolidation in cementitious and adhesive products vendors' ownership lately, there are surely lots of competing brands' products that will do just as well.

        HTH,

        Jim Getaz

        Precast Engineer