Anchoring wrought iron railings to concrete porches and stucco or concrete block walls can be a real problem. Pourable expansion cement offers a simple, reliable solution. It sets to usable hardness in half an hour and has twice the compressive strength of ordinary concrete. Expansion cement comes in powder form and can be mixed either to the consistency of putty for vertical work, or to pouring consistency for work on horizontal surfaces.
If you are working in old concrete, use a masonry drill or roto-hammer bit 1/2-in. larger than the diameter or diagonal measurement of the post to be installed, and drill a hole at least 2 in. deep. Rock and rotate the drill slightly to enlarge the bottom of the hole, then clean it out thoroughly, using an air compressor, bicycle pump or vacuum cleaner. Dampen the hole with water, set the post in place, and fill it with expansion cement.
—Geoff Alexander, Berkeley, CA
Edited by Charles Miller
From Fine Homebuilding #3
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View Comments
How old is this tip?
How much expansive force does the expansion cement create?
There's an expansive material called Dexpan that's sold expressly for the purpose of breaking up concrete. Given that the holes for railings and the like are usually close to the edge of the slab, I can see the potential for breakage.
http://www.dexpan.com/dexpan-how-to-use-dexpan-non-explosive-controlled-demolition-agent-breaking.aspx