J.K.Reynolds
Structural
- May 24, 2021
- 1
Need some help with a concrete overlay design.
Just completed a job walk and the request is to overlay a new concrete slab on top of an existing 100ftx300ft slab. The existing slab does not appear to have any significant structural damage and the only reason for the request is to provide a different drainage design versus the original design. Looking at it briefly in the field, the new slab will need to be at a minimum 6" thick at the LP El to accommodate prefab HDPE Trench Inserts.
My first thought was that this will be a simple task, however I started to read ACI 325 and it appears a little more went into the design than I originally expected. Working out the invert elevations and locating the trench should be fairly straight forward. Where I would like some insight are on the topics below:
***Bonded Versus Unbonded Application. - The existing slab seems fine. My thoughts were to roughen existing surface and provide a bonding agent before applying new concrete.
***Reinforcement - To help with Temp Shrinkage, my thoughts were to include WWF.
***Joint Spacing - I understand this will be critical to manage shrinking. Do I need to try to match the joints on the existing slab?
***Concrete Mix Design - Need to provide a concrete design that will reduce shrinkage.
***Anything else not on my radar?***
Anyone that has experience on this type of design and could provide guidance would be greatly appreciated!
Just completed a job walk and the request is to overlay a new concrete slab on top of an existing 100ftx300ft slab. The existing slab does not appear to have any significant structural damage and the only reason for the request is to provide a different drainage design versus the original design. Looking at it briefly in the field, the new slab will need to be at a minimum 6" thick at the LP El to accommodate prefab HDPE Trench Inserts.
My first thought was that this will be a simple task, however I started to read ACI 325 and it appears a little more went into the design than I originally expected. Working out the invert elevations and locating the trench should be fairly straight forward. Where I would like some insight are on the topics below:
***Bonded Versus Unbonded Application. - The existing slab seems fine. My thoughts were to roughen existing surface and provide a bonding agent before applying new concrete.
***Reinforcement - To help with Temp Shrinkage, my thoughts were to include WWF.
***Joint Spacing - I understand this will be critical to manage shrinking. Do I need to try to match the joints on the existing slab?
***Concrete Mix Design - Need to provide a concrete design that will reduce shrinkage.
***Anything else not on my radar?***
Anyone that has experience on this type of design and could provide guidance would be greatly appreciated!
