pbc825
Structural
- May 21, 2013
- 103
I’ve got a good question for everyone. How long does concrete last?
The context of the question is long-term mine opening closures. We’re contracted to close mine openings for a governmental regulator. We’re currently designing them to last a LONG time with stainless steel. They’re not back-filled and everything is available for inspection.
Some openings have an existing vertical concrete collar and a horizontal cover. Wall thickness is around 10” (250mm). Cover thickness is greater. Vertical concrete was back-filled. It currently looks brand new. The collar was constructed in the early 1960’s so its 50+ years old today. Typically the vertical concrete is heavily reinforced 4% range.
I seek to remove the horizontal concrete cover, foam fill the collar and replace the cover with a stainless steel cover. The reason for foam fill is to make the walls free of normal stress from bending moment induced from soil pressure.
So now the concrete is used for vertical support on the cover (for which it’s grossly oversized) and is not subject to typical environmental exposure. The environment does have freeze-thaw exposure.
Two questions.
1) what’s your prediction on how much longevity we have before the concrete collar would require replacement? Recall that it’s now 50+ years old and looks great. Also, we need approximately 1/2” of concrete for structural purposes.
2) is there any research to back up any predictions? For this client we’re going to need it for them to believe us. Without this “backup”, the client will be spending much more than I think they should be on vertical skirting, long columns and landscaping to prevent the backfill.
Thank you in advance.
The context of the question is long-term mine opening closures. We’re contracted to close mine openings for a governmental regulator. We’re currently designing them to last a LONG time with stainless steel. They’re not back-filled and everything is available for inspection.
Some openings have an existing vertical concrete collar and a horizontal cover. Wall thickness is around 10” (250mm). Cover thickness is greater. Vertical concrete was back-filled. It currently looks brand new. The collar was constructed in the early 1960’s so its 50+ years old today. Typically the vertical concrete is heavily reinforced 4% range.
I seek to remove the horizontal concrete cover, foam fill the collar and replace the cover with a stainless steel cover. The reason for foam fill is to make the walls free of normal stress from bending moment induced from soil pressure.
So now the concrete is used for vertical support on the cover (for which it’s grossly oversized) and is not subject to typical environmental exposure. The environment does have freeze-thaw exposure.
Two questions.
1) what’s your prediction on how much longevity we have before the concrete collar would require replacement? Recall that it’s now 50+ years old and looks great. Also, we need approximately 1/2” of concrete for structural purposes.
2) is there any research to back up any predictions? For this client we’re going to need it for them to believe us. Without this “backup”, the client will be spending much more than I think they should be on vertical skirting, long columns and landscaping to prevent the backfill.
Thank you in advance.
