Use of chemical injection for waterproofing exisitng concrete works 2

[Hsang]

I inspected a commercial building where part of the first floor is exposed to the weather and a ground floor below of carparking area and offices. The first floor slab is partly of conventional reinforced and steel deckform concrete slabs, beams and columns. New pavers were recently installed in the last 4 years to the first floor. After 20 years, stormwater on the first floor penetrated the slabs at crack locations (evident by the presence of ettringite on the concrete), pipe locations, movement joints, other service locations (eg stormwater pits), planter boxes watering pipes and the like. I am persuaded by the client to come up with a system of waterproofing the concrete works without removing the exisitng pavers (on cement bedding) on the first floor. I intend to undertake levels survey of the first floor surface, some intrusive exploratory works to understand the surface runoff flow paths and the probable causes for the leaks etc etc. I am let to understand the original slab was waterproofed using dentritic crystals.

For the water proofing of the slab/beams concrete works (excluding pipe penetrations), I am considering the use of pressure injecting hard gel at regular centres in the affected concrete areas. Can someone enlighten me on how I can get my hands on publications that explains how to consider the use of such chemical injection methods and how to specific them. Rgds

 

[Ingenuity]

I am not sure what you mean when you refer "pressure injecting hard gel".

It is more common to consider the use of 1) non-structural urethane injection (hydrophobic or hydrophilic) for active/heavy water flow, or 2) structural crack injection via epoxy resins, with a water-tolerant resin?

Given 20 years of water ingress, it is prudent to investigate any corrosion of embedded reinforcement BEFORE undertaking repair or waterproofing work.

"...steel deckform concrete slabs..."

Does this refer to the use of metal/steel pan decking used as permanent formwork? If so, with significant water ingress from the top surfaces water may have accumulated on the top of pan and caused corrosion.

Doing permanent waterproofing from the "negative" side of a slab (or wall) is difficult.

 

[DamsInc]

We have used hydophilic polyurathane injection for waterproofing cracks in concrete walls. It works ok. The problem is that once you seal one visible crack, the water will migrate to another, unseen crack and all you have done is redirect the water to the next most permeable location. It could work well depending on the quality of the concrete and amount of water you are dealing with. As a first step, it's not a bad solution since it's easy to do and relatively inexpensive compared to a full blown waterproofing solution. Just don't expect any miracles.

 

[Hsang]

Thanks Ingenuity & DamsInc for your thoughts. They are appreciated. I am aware of the issues of corrosion and hence the intrusive exploratory works discussed. I believe I will be able to manage them. The steel deckform refers to are the steel pan deck (bondek) and are probably structural. I am organising the discovery of the drawings from the local council for inspection. I am considering the use of polyurethanes/acrylates for waterproofing (hence my term 'injecting hard gel' in my first thread which, in hind sight may be misleading and poorly described. My problem is in the specification of the Work to ensure the client's interests are protected and that the issues eg (the water being directed to the next 'exit' point/s)which in the mind of the client may believe we have 'made the problem worse'. Hence my reference to 'publications that explains how to ...... specify them'. I will be advising the client of the pros and cons of the system cf the conventional physical tanking process. I am also considering pressure testing the slab with water using packers at selected areas to provide an indicator the flow paths (ie leaks from cracks/cold joints etc in the concrete).

questions in my mind include:
Do I specify the chemicals? Do I lean on Sika, TAM and the like to assist me in the specification or leave the choice of chemicals to the Contractor (ie performance spec)?
How do I minimise wastage of the chemicals (eg sealing of the cracks on the underside of slab to prevent the chemical from coming out of the slab instead of chasing the cracks and sealing them)?
Are there publications that will assist me in my understanding/specification?
Rgds

 

[amlinerrichard]

Try to find suppliers of Avanti Grouts and DeNeef Grouts. they come either hydrophilic or hydro phobic. In colder climates I have heard that beeswax, heated and pours in cracks does a good job.

 

[Ingenuity]

Hsang,

Where are you located?

You used the name "bondek" so are you in Australia?

Any product or brand-type recommendations given here are going to be specific to local availability.

If this project is going to be bid I would go performance-based specification, provided you fully explain the parameters and outcomes to which the contractors are to bid. Such performance specs enable you to stay away from specifying any "means and methods".

Often specialised local contractors will provide you some advice that can assist with getting a spec together to which all bidding contractor can competitively bid using techniques they individually feel is appropriate.

 

[Hsang]

Thanks amlinerrichard and Ingenuity for your contributions.
I am in Australia. Temperature is mid 40s[sup]o[/sup]C in summer. I will consider the use of polyurethanes/acrylates for waterproofing as one feasible options. I will document one or more options for tender following review of report by the client (eg traditional tanking and the chemical method discussed above). Of course the traditional tanking will result in the removal of the 'recently' laid pavers. The specification will be performance based.
The repair of the concrete at locations will precede the waterproofing works.
Thanks all. Rgds.

 

[Hsang]

Two photographs of corrosion of steel deckform and water leak through slab/beam.
Rgds

 

[Ron]

Just because the owner wants something doesn't mean that it's practical, reasonable or even do-able. You are the professional and you will be judged by the success of whatever method you choose.

Injecting anything into concrete to achieve consistent waterproofing is a shot in the dark and likely will not be successful, particularly for the long term. Concrete is non-homogeneous in density and has a variable moisture content internally, particularly near the location of leaks. This will make the migration and absorption of any type of hygrophobic injection material difficult and inconsistent. Further, injection pressure will vary with the concrete density. Absorption will vary with the moisture content.

Remove the pavers, put a proper membrane on the concrete and replace the pavers.

 

[CELinOttawa]

I vote membrane as well.

 

[hokie66]

I also agree with Ron. You will likely spend a lot of money, time, and effort chasing your tail. Decks cannot be waterproofed with "dendritic crystals".

 

[JedClampett]

If you want to see an extreme example of poorly repaired roof leaks causing secondary issues. See Algo Centre Mall collapse.
There's a link to a report that is excruciatingly complete.

 

[Hsang]

Thanks for all the comments. Interesting views. This is engineering and different views are expected.

My take is that conventional tanking is tried and proven when they are properly installed. However the use of polyurethanes/acrylates for waterproofing has been around for a while with international brand names. The use of chemical injection is that the control is in the hand of the specialist contractor using chemicals that we do not have 'control' (eg amount of chemical required, setting time to 'chase' the cracks in the concrete etc).

The advantage of the injection method is that the whole place will not need to be closed to the public (being an office block) during the remedial work and hopefully cost effective cf the traditional tanking process. I will advise the clients of the pros and cons in the use of chemical injection for waterproofing (amount of chemicals cannot be accurately ascertained, no physical confirmation etc). It is probable I will document both the traditional tanking and the chemical injection methods for costing purpose.

Of course investigation of the corrosion in the structural deckform and reinforcing bars/welded fabric is required before tanking of the area is carried out. Some areas will require exposure and confirmation (eg movement joints, pipe penetration and sealing etc).

Thanks all again. Rgds

 

[dcarr82775]

Agree with Ron also.