Pouring new concrete slabs in brownfields
Pouring new concrete slabs in brownfields
(OP)
I am an agricultural engineer working on a development in a brownfield site in Philadelphia. The project is the construction of a 10,000 square foot hydroponics facility that will include several 100'x 20' low-walled reservoirs. The site is over 75 years old, the original slab is still present and in terrible shape. Is there a manner in which new concrete slabs can be formed on-site without removing the old concrete slabs. It is vital that the reservoirs not crack.





RE: Pouring new concrete slabs in brownfields
Carl Bauer
www.bauerconsultbotswana.com
RE: Pouring new concrete slabs in brownfields
RE: Pouring new concrete slabs in brownfields
Thank you for that information. I hadn't considered the strength the side beams will be adding to the structure, but it makes great sense.
There are areas on the old slab where settlememt has taken place, where chunks are missing and where pieces of old foundation walls have been left in place. I am assuming that we will be able to grade the area with fill to keep the thickness of the new slab from variating too greatly over its area. Do you think this is important, and do you think it will work (again the goal is to keep the slab from cracking due to inequalities in thickness).
dik-
a brownfield is an urban parcel that was the former site of some industrial facility. Normally these parcels (to be dubbed brownfields) have undergone some demolition, and an environmental assessment that has characterized the property as a major environmental risk. Often they are cleaned by the USEPA or state agency to some degree of safety but are still difficult properties to redevelop - often because they are located in blighted neighborhoods. Philadelphia, like a lot of large cities has many acres, often hundreds of acres, of these properties available for development. Ironically, agriculture may be one of the best uses of these lots.
RE: Pouring new concrete slabs in brownfields
Can you advise the client that due to the uncertainty of the founding material that differential movement may occur; this is unlikely to be catastrophic and that if movement occurs then it will have to be addressed at that time. Can you detail a level of ductility into the structure that will accommodate slight movement (using liners, etc.?)
RE: Pouring new concrete slabs in brownfields
The reservoir will either have to be designed as waterproof concrete (limiting crack widths) or have liners. As dik suggested the liner option might be the one to go for since you just can't be sure of the subgrade. This would then allow some cracking.
Carl Bauer
www.bauerconsultbotswana.com
RE: Pouring new concrete slabs in brownfields
When you suggest a mat type foundation - are you suggesting that the reinforcement be greater than for an ordinary slab. I had been expecting that we should have to do this. Is there a guide I can follow for increasing the reinforcement. As you know, there won't be much weight to bear (12" of water)but if increased reinforcement will help our chances in avoiding multiple cracks I would like to investigate it. Is it also advisable to strike contraction joints (these will not interfere with the function of the reservoir).
We are about to begin construction of a prototype to test the design. It will only be one-quarter of the size of the design model but hopefully we will learn a lot about the capabilities of the waterproofing, and our ability to adequately prepare the old surface to support the new slabs.
RE: Pouring new concrete slabs in brownfields
The 12" of water does not seem to be a very high load and should be able to be supported by almost any reasonable base material.
Will take a gander to see what waterproofing admixtures can be used... even for Olympic sized pools, I've just used regular concrete...