The Water Proofing Conundrum

1/26/2012 3:33:26 PM #

I have watched the compression question for quite a while. When I was trained in the business, I asked about the 2500 psi spec. At the time we were using an 8 bag mix with no problems. I was told that the spec was used in the contract to protect us in court. If the design could function with 2500# concrete and you applied 4500# concrete, all was good. Almost anything could go wrong and the mix would still hit 2500 psi. The goal was NEVER to aim for the 2500 mark.

As far as the waterproofing question---it is basically a sales question. What do you feel good about selling? Waterproofing typically adds a minimum of $500.00 to the costs, but if you do it, you have one more thing to seperate your firm from the competition. Can you get the extra money? Do we need both belt and suspenders?

Rob Lane

1/26/2012 3:57:51 PM #

How do you get from the same to better?
You have to be different.

Scott BAir

1/26/2012 6:44:12 PM #

To say concrete at a compressive strength of 4,000 psi makes you feel comfortable in regards to structure or water proofing ability is wrong.  Compressively speaking you can have a strong concrete mix design "6-7,000 psi" but the actual factors of whether the material is water tight is based on its density more than anything.  Yes higher compressive strength materials typically demonstrate higher resistance to permeation, but the issue of diffusion "permeation through pores and molecular gaps" is solved on the molecular level.  

I see the permeability of concrete as a larger problem than we like to admit.  The negative side affects are seen in colder climates such as the Northeast more often than in Southern California.  Trapped water freezes, expands and damages the structure and anything attached, plain and simple.  

By absorbing water you are in fact absorbing carbon dioxide and acidic compounds which results in lowering the pH levels around the steel reinforcement resulting in corrosive cells to form "rust".  Iron oxides developing on steel placed too close to the surface of the concrete equates to spalling.

As well you can have plaster delaminating as the surface conditions "chemistry" change beneath the finish.  We all know these are not the most common issues we face as builders but we do know deep down they are issues, just not life and death.

If money was no issue you could use a crystalline based admixture every time, I'm just not sure its economical.  High water tables always remind us we are building a structure underground that will potentially be exposed to water constantly.  In these cases, maybe the integrity of the builder should kick in and he explain to the customer why an admixture is needed.

My final point is this; Even if you could make the statement at "X psi" shotcrete/gunite is 99.9% moisture resistant, as Bill stated above, human effort in applying the material still is a factor.  Lets be honest, after 30 yds of shooting and 10 more to go, your nozzleman is not going to be following the text book.

Remy Genot

Remy Genot

1/26/2012 10:37:24 PM #

It is simple, let us not rely on the assumptions of what could or might happen during the pool building process. Let us instead rely on the experience of experts (like Skip Phillips) who have been hired to do forensic testing of failed projects (100's of them in fact) and has determined that rarely is a concrete shell installed 100% correct, and rarely is it 100% waterproof.  It is that issue that is also often the cause of simple or catastrophic failures of these projects.
Let us then look to that data and the difficulty of the projects we construct, and recognize that the only proper way to construct a pool vessel intended to hold water (or salt water) and protect that structure is to water proof it.  Period!  The data tells us that it is a necessity, the chemistry tells us it is a necessity; don't wait till I lawyer tells you it was necessary.  

Rick Chafey

1/31/2012 10:22:06 PM #

Rick has put it very well.  This is an ongoing discussion that surfaces yearly. Kudos to Drakley for his expert oppinion however to many variables exist. If your going to put 150K in glass tile alone into a new vessel, You had better cover all the bases.  Install a waterproofing barrier can not hurt anything.    

Peter Langevin

2/7/2012 10:45:58 AM #

This discussion alone raises the bar for pool construction and I am glad Aqua Mag keeps this in the forefront. I want to add a history comment here for shotcrete in the pool industry.  Years ago, ( decades ago ) a lot of pool builders did their own shot work, either wet or dry.  Quality control was much more prevalent than it is today.  We service a number of pools with only a gunned surface ( built in the 50's and 60"s. )  No leaks and no damp proofing  needed.  Concrete installed correctly has no need for today's sealing products.  However, what we have learned ( including me thru ACI examinations ) is that most subcontractors who shoot for the pool industry have settled on a performance criteria that is less than what the ACI expectations are.  Further more, engineered drawings are now designed around cost of inspections or a savings of cement bags.  This lowering of the bar necessitates  damp proofing and continued long enough sets a standard, albeit lousy, for pool construction.  This is where we are today.  Lousy concrete needs damp proofing to a point where we need to damp proof all shells just in case we have a fault.  I don't buy it.  Nor do I recommend that anyone not damp proof their $ 150k tile job.  My argument is and has been that for years shot products were water tight without any surface material added.  Compressive values averaged, repeat averaged, 6000 psi.  ( current ACI expected values in shotcrete are between 4000-8000+ psi )  Why we have accepted something less has to do with a lack of education and acceptance of substandard practices.  So, do I recommend damp proofing?  Absolutely!  I just don't like the idea that its a necessity of shotcrete construction because it never was in the past and should not be now.  Shotcrete is the ideal way to place concrete- a void free, well compacted dense in place structural member with low porosity and high strength which yields water tightness.  We do our own shotcrete with our own certified nozzlemen and I'm sure that's a huge difference between our product and others.   Just don't tell me damp proofing ( water proofing is the incorrect term because nothing is water proof over infinite time and under infinite  pressure ) is a necessity because its not.  Our last large tile job was 9,000 square feet HS featured in Water Shapes mag " Head of the Class "  We use the tile setting bed as the only bond to the shell.  No fingers crossed here and no lawsuit looming)

William Drakeley

2/7/2012 3:51:29 PM #

In my mind the permeability of shotcrete has no bearing on the ability of a pool to remain leak free when 99.9% of the time the leaks occur due to improper sealing of the penetrations through the shotcrete shell.

Mike Davis, Davis Pools of Washougal

2/7/2012 6:12:28 PM #

Bill,
Again your expertise is well noted in this field.  Not many or maybe none of us shoot our own shells.  I commend you on your passion in this area.  I do believe that raising the bar is a necessary step in the evolution of the industry.  We presently have one local shotcrete company in Orange County CA. that has one certified nozzelman.  That maybe hard to believe.   I have worked along side them for many years and have gotten in a habit of pointing out defects in their process. Our lab tests come back at 6K or higher on a regular basis.  With that said, The placement is in question at times.  Some areas we work in push the boundries on setting time.  For that reason alone I have decided to use waterproofing agents and in some cases use crystalline additives.  As far as concrete strenght is concerned, 4000 psi should be the standard and many cities have already addopted this as their minimum for over the counter engineering.  
If anyone knows of an installer that can raise the bar in my area please let me know.

Peter

2/9/2012 2:50:47 PM #

There still appears to be confusion between the terms "permeability" & "waterproof" as they relate to concrete.

Increased concrete densities provide for stronger structures (for which I am an advocate) and they REDUCE concrete's permeability, however they DO NOT render it WATERPROOF!

We need to stop alluding to the fact that higher psi concrete's are WATERPROOF - THEY ARE NOT WATERPROOF.  They ARE less permeable, but water will still weep through the concrete (just slower).

Bill Drakeley needs to stop confusing permeable and waterproof.

None of the following (references in my personal library) state that higher density concretes are "WATERPROOF."

Building Code Requirements for Structural Concrete (ACI 318M-08)
Steel Reinforced Concrete Structures, Mohamed A. El-Reedy (2008)
Reinforced Concrete Designers Handbook, 10th Ed Reynold & Steedman
Engineering Concrete Mix Designs & Test Methods, Irving, 1999
Advanced Concrete Technology Vol. #1 Constituent Materials, Newman & Choo, 2003
Advanced Concrete Technology Vol. #3 Processes, Newman & Choo, 2003
Advanced Concrete Technology Vol. #4 Testing & Quality, Newman & Choo, 2003
ACI 201.2R-01 Guide to Durable Concrete
Reinforced Concrete Design Theory & Examples, Macginley, 2003
Masonry and Concrete for Residential Construction, Beall, 2004
ASTM Steel Handbook, 3rd Ed, Bringas, 2002
Reinforcement for Concrete — Materials & Applications, ACI Educational Bulletin #2, 2006
ACI 506R - Guide to Shotcrete

Though one may be comfortable with the low permeability of 9,000 psi concrete, other trade standards specify the use of waterproof membranes (TCNA, CTIOA,).  Ignoring these other standards is as egregious as shooting a 2,500 psi pool shell!

The mere use of high density concrete does not provide protection from hydrogen sulfide or chloride corrosion of the concrete.  Protection from these ravages of nature can only be provided with special mix designs, concretes, admixtures and/or waterproof membranes.

Paolo Benedetti

2/14/2012 11:59:46 AM #

Mr Benedetti needs glasses.  We already discussed how nothing is water proof in the above blog.  Shooting techniques and performance of concrete should be water tight to a point where water loss equals that days evaporation rate.  High psi values indicate concrete is dense, strong, has a low porosity level and able to protect is reinforcement.

These are all facts w/o exclamations and uptightness))))


Bill Drakeley

William Drakeley

2/15/2012 12:18:27 PM #

MR. BENEDETTI put on his coke bottle glasses, Increased the font size on his computer monitor, turned on the "text to speach" software and opened his braille ASTM and ACI reference manuals.

I clearly read wherein Mr. Drakeley admitted that he chose to ignore the published installation standards of the TCNA and CTIOA.  Both STILL require additional waterproofing measures under tile in vessels, tubs, showers, etc.  Until those standards are repealed or modified, one cannot simply chose to ignore them.

I know that Mr. Drakeley is aware that the currently accepted ACI permeability tests have inherent flaws (we have discussed this).  The chloride ion penetration test (ASTM C1202) does not measure how rapidly the ions penetrate.  Nor does the test account for variations in hydrostatic pressures, a variable that increases the permeability as the hydrostatic pressures increase.

Though mix design and compressive strengths can deliver a sufficient low value of
chloride ion penetration, the use of this option without demonstrable in place chloride ion resistance, is beyond the scope of the current ACI 318 (which is the controlling document of most Building Codes).  

Both of us build concrete structures other than swimming pools, so Mr. Drakeley should be aware that WATERPROOFING is also required to protect concrete (and reinforcement) from sulfates, hydrogen sulfide and chloride degradation.   Waterproofing is oftentimes applied to the soils prior to the placement of reinforcement or to the outside of subterranean concrete structures prior to back-filling.  

The last time I put on my glasses, most swimming pools were subterranean.

Paolo Benedetti

2/17/2012 6:18:09 PM #

Bill/Paolo,
I'm sure glad you're both on my team!!!!
Skip

Skip Phillips

2/20/2012 9:15:58 AM #

Lets talk about testing shall we?

1.  To my knowledge, no association for tile or finished materials ( tubs, showers etc ) that require a water proofing ( again the wrong the term - should be damp proofing ) has ever conducted thorough, in depth tests on concrete correctly placed by the shotcrete process with in-place values above 4000 psi minimum ( not in ACI 506, ASA or ASTM ).  Therefore, that association's standard for protection does not have a direct correlation to shotcrete and is incorrectly stated because the substrates that the finished products are connected to are entirely different than that of  shotcrete and ACI 506.  ( i.e. w/c ratio, deflection, porosity, expansion etc )
2.  Except for ACI 506, building guides or trades that require water proofing from sulfate protection or ion degradation are not considering shotcrete placement techniques when it comes to encapsulation of the reinforcement or the concrete itself.  If they did, water proofing would not be as prevalent because of the low permeability and low porosity levels demonstrated by shotcrete encapsulation.
3. Soil protection, soil nailing, creek channelization is not a subterranean process that utilizes correct mixtures for shotcrete.  These installations ( according to the contractors that do this type of work from ASA ) are dumbed down in mix and w/c ratios to be competitive in the market place.  Never compare this to pool construction
4. Chloride Ion protection ( as Paul correctly alludes to ) is not an in place test.  Its a mix design test in a lab.   Collecting an in-place sample for an ion penetration test for pool would be extremely difficult and has not been done in the pool industry.  Referring to it for pool results of any kind would not be substantiated.

My point is this:  Don't be thrown off or think you need all these additions to your pool product.  There are many codes and many, many agencies that require this or that water ( damp ) proofing.   When you take a hard look at the evidence, very rarely does the concrete tested have to do with proper in-place shotcrete.  The academic and spec writing community always confuse this issue.  Cast, curb and gutter, or hand placed is a different animal than shotcrete and blanket statements of protection are not appropriate in correct shotctete technology.

Bill Drakeley.  

William Drakeley

2/20/2012 2:15:59 PM #

Bill-

I respectfully disagree.  Our industry is hostage, like it or not, to all applicable trade standards and procedures.  Case in point:  I've been retained as an expert witness in a civil action representing the tile installer on a pool.  Even though there are serious questions as to the engineering and execution of the shell, and there is no evidence the pool leaks through the waterline tile, his application failed to meet the tile industry criteria for waterproofing behind his work.  Checkmate- the only question is how much he owes.  We should promote compliance with all relevant standards- bar none, and promote that fact, just as we do the 4,000p.s.i. compressive minimum.

Skip Phillips

2/20/2012 4:02:39 PM #

Skip,


We are held hostage and I don't dispute your case.  However, light needs to be shed on this misnomer of information that falsely states all finish applications are treated the same solely because of the relationship with concrete without regard for the type of placed concrete.  

William Drakeley

2/23/2012 9:50:03 AM #

Bill,

THIS IS THE EXACT POINT THAT I AM MAKING.

There is no IN PLACE test for the measurement of permeability (chloride ion is for testing mix designs), therefore there is no way do an "end around run" on these other standards.

Until there is a SCIENTIFIC METHOD of proving "in situ" (in place) permeability, we are hostage to ALL of the applicable standards.

Waterproofing measures are not expensive nor labor intensive, so why not just comply with the other trade standards...

...at least until someone develops an "in situ nuclear solar refractive hydration resonance penetratometer."

paolo benedetti