bonding new concrete to old load bearing colums


Old 03-29-18, 10:03 AM
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Join Date: Mar 2018
Location: Puerto Rico
Posts: 1
bonding new concrete to old load bearing colums

I am purchasing a lot with 3 year old foundation and partially poured columns to support concrete second floor.
Any tricks to bond the new concrete to the existing columns that have 2 feet of rebar extending out? Do i need to clean the rebar and the top of the existing columns? Any bonding agent I need to use?
I would hate to just bulldoze and start over.
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Old 04-06-18, 07:55 PM
Join Date: Dec 2013
Location: usa
Posts: 1,333
diamond grind off the tops of the conc columns to expose new conc,,, wire brush (4" grinder) to remove scale & rust,,, use a bond promoter, form, & place new conc
Old 04-07-18, 06:05 AM
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Location: NC, USA
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What stadry described will work well. In many parts of the world adding onto old columns is commonly done and they rarely do anything more than put up the forms and pour concrete. Stadry's method will insure that the new has a better bond to the old but the extended rebar is the primary thing that will be holding the new in place.
Old 04-07-18, 01:00 PM
Join Date: Dec 2013
Location: usa
Posts: 1,333
the new steel reinforced conc will act as another column sitting on an existing column,,, the steel just keeps it in lateral position,,, steel doesn't add much compressive strength (if any) but does add flexural strength,,, we've done it this way due to job specs,,, when taking core samples, 1/2 pass'd & 1/2 didn't[ far's an actual 'bond'

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