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Waterproof Concrete.
A waterproof concrete basement, properly designed, properly prepared, properly reinforced, properly poured, properly compacted and properly cured under proper supervision is the best material with which to build a new basement.
It will be fully waterproof with waterproof joints and nothing, whether scaffolders carrying poles, bricklayers and their heavy boots or craning materials around will damage it.
You may be sick of reading about it on this web site, but in 2022 BS8102 changed. A complete U turn. Internal drainage is out. Building your structure to be waterproof is in.
Building your basement, properly and with care, with waterproof concrete is the simplest and cheapest solution most likely to succeed.
But the design team, main contractors and sub contractors must all change their ways, because their ways have been failing clients for too long.
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This text box is repeated on other pages.
I have a number of large text boxes each repeated a few times throughout this web site, because each topic is very important and I want readers finding different web pages the first time they find me to find all the text boxes before they move on.
Any box with same title and same border colour will always be identical.
I hope you find you can read pages more usefully and more quickly if you recognise a text box as one you remember.
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Waterproof Concrete.
Waterproof concrete is a specific mix of completely normal aggregates, cement and water.
Waterproof concrete has extra sand to completely fill the spaces between the stones.
Waterproof concrete has extra cement to completely fill all the spaces between the sand.
Waterproof concrete has a lot less water so that grains of cement are not pushed apart. Grains of cement almost touch neighbours in the fresh, wet waterproof concrete mix.
Normally concrete has more water that pushes grains of cement apart reducing the friction and adding workability, which is why extra water is very popular with labourers. More water significantly reduces the amount of work they need to do.
But more water weakens the concrete, increases drying shrinkage cracking and makes concrete more porous. The problems caused by more water in concrete are unpopular with clients.
As the surface of each grain of cement blends with the surface of the water against it, gel is formed with a slight expansion. The gel turns into long, thin, tangled (interlocking) crystals.
Therefore, the essential difference between waterproof concrete and the rest is:
a complete sheet of interlocked crystals, continuous around and between every grain of cement throughout the entire batch of concrete, made soon after the concrete begins to set.
As more cement reacts with more water, this continuous sheet of interlocked crystals thickens to a mat.
Rather than, with more water:
Grains of cement surrounded by interlocked crystals that, for a long time depending on how much water pushed cement grains apart, have no connection with crystals surrounding neighbouring grains.
Until crystals interlock throughout the batch of concrete, no concrete has been produced.
Depending on how much extra water there is, the eventual continuous mat of crystals will be thinner and less dense being watered down by remaining water not used to cure any cement.
The mat in waterproof concrete gets thicker and thicker until remnants of grains of cement are left trapped one side of the mat and remnants of water are left, sealed in tiny pockets, the other side of the mat. Sometimes called the skeleton.
When no more water can reach remaining cement grain all reaction stops. The concrete is waterproof.
That is ....
until ....
there is a crack.
Concrete warms up and expands when it cures and cools down and shrinks as it cools, usually a day or two later.
It is inevitable that concrete will crack upon cooling in parts of a concrete structure that are restrained at the ends. In my experience, a 20m long basement retaining wall of waterproof concrete will shrink about 3mm.
The 'trick' is to have sufficient horizontal steel reinforcing bars that grip the concrete either side of a crack instantly and prevent that crack opening more than 0.2mm.
This will make the concrete crack again and again until all the cracks add up to the total thermal shrinkage which, in my example, is 3mm over 20m, which requires 15 cracks if each is 0.2mm wide.
When waterproof concrete cracks it is the continuous mat of interlocked crystals that cracks. Unused water will find remnant of cement grain and the curing process begins again. A crack up to 0.2mm wide will completely heal. This is called autogenous healing.
Some other concrete elements, such as basement floor slabs, are not restrained and can expand then shrink as a whole without cracking.
Non-waterproof concrete will always be weaker and more porous than waterproof concrete because the waterproof concrete is a better blend of solids and less water pushing the solids apart. Increasing the water increases the amount of cement that is turned into crystals but extra water reduces the amount of crystals surrounding one grain of cement that interlock with crystals surrounding each neighbour.
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Proving that you have Waterproof Concrete.
BS 8102 deals with the waterproofing of beneath ground structures.
From 9.1 of BS 8102:2022 on page 36.
"Concrete structures containing a water resisting admixture should be deemed to have a lower degree
of water / vapour transmission when the design of the concrete mix and casting of the structure is
adequately supervised and the admixture is assessed and certified (see 9.2.1.3)."
I deal with 9.2.1.3 in the text box 'What academia says about Waterproof Concrete'.
"Where the waterproofing admixture has been assessed and certified by a UKAS-accredited body or
a European Technical Approval body, certification information should be referred to for guidance on
use and the extent or limitation of technical benefit."
On page 53 of the new BS 8102:2022, BS EN 12390 part 8 is quoted.
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Click on this image to open an original test certificate.
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This is the start page on the British Standards web site for BS EN 12390, Testing Of Hardened Concrete.
Part 3 is used thousands of times every week: Compressive strength of test specimens
Part 8 is Depth of penetration of water under pressure.
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Here is a photographed extract from my copy of "Advanced Concrete Technology", the volume called "Processes", the Chapter called "Concrete construction for liquid-retaining structures" by Tony Threlfall, 2003, Butterworth-Heinemann. Page 16.2.
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Click on this image to be able to read the text from the whole page.
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The pass mark for BS EN 12390 part 8, depth of penetration of water into hardened concrete, is 20mm.
If your architect, structural engineer, building control officer, warranty provider or lender insist on you using a product with a BBA certificate. Fight back. They will think they are still correct trying to meet the 2009 version of BS 8102. They are not meeting BS8102:2022. Go here to the
BS8102 page where I reveal the truth behind BBA certificates. This is the same as the link above.
Nowhere does BS 8102:2022 mention BBA or BBA certificates.
Another certificate. ESG became Socotec between 2016 and 2018, but they are from the same lab.
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What Academia says about Waterproof Concrete.
First, I promised elsewhere to return to 9.2.1.3 in BS8102:2022.
"
9.2.1.3 Concrete containing water resisting admixtures
COMMENTARY ON 9.2.1.3
There is a range of products, generally categorized as water resisting admixtures, which seek various ways to increase the inherent resistance of concrete to water and water vapour. As the mechanisms used each product to achieve these aims are quite diverse, it is not possible in this British Standard to give specific guidance on their use.
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From the summary on page 55 of the report cited below: "Section 2 lists the types of materials that may be categorised as water-resisting admixtures and describes some of the mechanisms by which they may resist water penetration. However, the working party was unable to obtain details of the constituents in most of the commercially available water-resisting admixtures."
and:
It seems that with regard to water-resisting admixtures the available information has not been expanded
on from what was available nearly 20 years ago when Neville (see Section 4) commented:
"Unfortunately, little information is available to make it possible to explain and classify the actions
involved so that reliance has to be based on the manufacturers' data coupled with experimental
evidence on the performance of any particular waterproofing admixture".
A working group of 18 academics, major contractors, engineers and consultants decided to investigate whether and how corrosion of steel reinforcement might be prevented when the reinforced concrete was formed against sea water in the Arabian Peninsular. They sought to avoid stainless steel reinforcement by finding out how concrete might be improved to reduce corrosion.
They published:
The influence of integral water-resisting admixtures on the durability of concrete. Concrete Society. 2013.
For all the years since 2013, I have had my eyes open looking for clues. Cement and anything else that might be harmful has to be declared on safety documents. Cement and cement substitutes, such as calcium carbonate, are present in several brands including, I believe, in Pudlo, Sika, Xypex, Kryton and Triton.
In addition, all the brands require their admixture to be added to a very dense mix of concrete with limited water content.
It is my assertion and firmly held belief that water resisting admixture suppliers all want their admixture added to already very water resistant concrete.
The same report quotes the Pudlo BBA certificate, which is fairly typical of many BBA certificates for so-called water-resisting admixtures.
Pudlo BBA Certificate 01/3842
"Concrete containing the product will have enhanced resistance to reinforcement corrosion when
compared to the equivalent plain concrete". "Under normal conditions of service, concrete
containing the product is more durable than an equivalent plain concrete".
If more cementitious powder is added to an already very dense mix of concrete, it will make that concrete a little bit more dense and reduce the water cement ratio very slightly and the claims made on the Pudlo BBA certificate are exactly what you would expect.
Obviously, it would be easier and cheaper to ask the readymix producer to increase the cement content by the same amount.
At an exhibition, Kryton told me their paper sack contained sand as well as cement because the sand was necessary to break the paper sack open quickly.
In section 4, the report reviews the available information. They found that all the BBA certificates for water-resisting admixtures were based upon tests with very different control concretes, making the different brands impossible to compare side by side.
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Pudlo immediately seems to be much better.
But, actually, if Pudlo had been added to the other control concretes it would have had similar results to those other brands.
Caltite is not here because the Caltite BBA certificate had less information. The report says the Caltite control concrete was not even as good as typical structural concrete. An academic paper cited in the report stated that Caltite only reduced transportation of water in much wetter concrete. It did nothing in low water concrete. This will be because Caltite contains no additional cement product. It contains a polymer emulsion that only works if it is thoroughly dried, which, obviously, has to be after the concrete has cured or else drying the concrete too early would affect its strength because the necessary chemical reactions would stop too soon.
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Page 16.
"
When the original tests were conducted, the aim was to demonstrate the increase in performance over respective control concretes and so the various materials cannot be directly compared. This is demonstrated by the range in 28-day compressive strengths for the concretes containing water-resisting admixtures (59-82 MPa) and their control concretes (47-63MPa). In addition, many of the water resisting admixtures achieve a reduction in water/cement ratio and caution must be exercised when assessing performance (see Section 5.3) to differentiate between the effect of the change in water/cement (which could be achieved with a water-reducing admixture) and any additional effects.
"
Nevertheless, the same report states on page 36 "water/cement ratio .... primary measure of water penetration and hence the durability of the concrete."
1988: "Theoretically, cement pastes with a water / cement ratio of <=0.5 achieve capillary discontinuity"
Lea, F. and Hewlett, P. (1988). Lea's chemistry of cement and concrete. 4th ed, p888. Oxford: Butterworth Heinemann.
But in 1988 no one had discovered how to add sufficient workability to such a dry mix. Super plasticisers could not be used in sufficient quantity without getting unwelcome effects, such as flash setting or weeks of retardation.
In 2011, the new edition of a long-respected university text stated more clearly than ever before that completely waterproof concrete could be produced without admixtures.
"concrete with a low water/cement ratio ... make the capillaries discontinuous" Neville, A.M. (2011). Properties of Concrete. 5th ed, p330. Harlow: Pearson Education.
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For years I have always used the concrete mix that is proven to always be completely impermeable. Without any proprietary admixture not proven to do anything but cost a lot of money.
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Waterproof Concrete Admixture Suppliers.
I found the guarantees given by some of these brands.
None of them seem to guarantee anything beyond what should be expected of structural concrete without any water-resisting admixture.
There are two examples of the Caltite guarantee on this web page. Where Caltite might have misled you is confusing the fact that Everdure Caltite, that contains a polymer, will waterproof non-waterproof concrete if the concrete is first kept moist inside and fully cured (which might take a month) then oven-baked long enough to dry the concrete and the polymer completely. They may have shown you an example where concrete above ground in Australia did exactly this. But beneath ground in Britain the polymer could not and will not work. Indeed, academic evidence is that if the polymer does not dry out it actually increases the transportation of water through concrete. The opposite effect.
You need to go to page 26 to find the exclusions in this Sika guarantee. Over the years I have had a few phone calls from people whose lives have been severely blighted by new basement construction suffering seemingly incurable waterproofing problems. All the worst sagas involved Sika. I was once called by someone calling himself a Sika sales manager who claimed this claim of mine was untrue. I was able to give him the phone number of one of these unhappy people. I didn't hear from him again.
If you go to the Kryton web site It all sounds very good until you realise that, like Sika, they are selling some extra cementitious powder and they promise only what extra cement will achieve. 0.25% extra cement does very little. But to say more water resistant, stronger, more durable would all be true even if only 0.25% true.
Pudlo and Xypex are selling extra cementitious powder as well. Let us not forget that the David Ball Group, that includes Pudlo, have a leak repair division as well.
Actually, the clever ingredient in every one of these admixtures is not a waterproofer but a powerful plasticiser. I am using the sixth I have found, each time having found better, and people who know tell me mine is best. Obviously, it is also the most expensive I found as well.
All powerful plasticisers are based on PCE, polycarboxylate ether, which is a very long molecule that clever chemicals can be fixed to.
Producers invent their own combinations of clever chemicals and patent them.
PCE with clever chemicals are used in concrete admixtures for a variety of uses, such as plasticiser, retarder and so on, and also in inks, paints and cosmetics.
Powerful plasticiser is a combination of PCE, electrostatic repulsion and glue.
The electrostatic repulsion isn't greatly different to naphthalene super plasticisers invented over 50 years ago. But with naphthalene it was liquid repelling liquid and its effect was limited.
PCE powerful plasticisers stick to the cement grains so that the solid cement grains are repulsed from each other and friction is reduced many times more than it was with the older technologies.
PCEs vary enormously. To have sourced a PCE is a long, long way from having sourced a very powerful plasticiser.
Beware of liquid PCEs. The 'glue' soon falls off after the stock arrives in the UK from the Far East. They effectively revert to a 50 year old super plasticiser technology in terms of effectiveness.
Never allow a liquid PCE plasticiser.
Every one of these product BBA certificates or the product literature or the safety document confirms that all allegedly waterproofing admixtures for concrete contain a powerful plasticiser. I believe the rest of what they say to be smoke and mirrors.
Since 2013 I have travelled to the USA and Asia many times looking for better and better plasticiser. The one I have now is very powerful indeed.
Waterproof concrete is so dense nothing can get through. But this very dense mix would be too dry to pump and properly compact. It (only) needs very powerful plasticiser.
I put my powerful plasticiser into the concrete at site.
It is the only way I can be sure that the batching plant limited the water content.
The concrete arrives with stones rattling loose in the drum and the concrete breaks apart as it is turned slowly.
My powder is added and I count 6 revolutions per cubic metre. It is quite clear, listening to the concrete, that my powder works because it becomes more workable, the stones stop rattling and the truck becomes stable and peaceful. Whereas it lurched at the start each time a huge volume of dry concrete crashed as the drum turned.
I feel that adding my admixture at site is the only way I can be certain the concrete has less water and that my plasticiser is definitely working.
None of the brands do this, as far as I am aware.
In particular, how could a liquid brand like Caltite know whether the tiny amount of essential powerful plasticiser within the 30 litres of mostly bituminous emulsion still works? Hasn't fallen to pieces?
Pudlo used a control concrete without admixture a lot more water resistant than the concrete other brands achieved even with their admixture.
Proving that waterproof concrete is at least as good as the Pudlo concrete with Pudlo in it. Or, perhaps waterproof concrete is a lot better. Perhaps it is zero and off the bottom of the chart by miles.
The proper test for waterproof concrete is BS EN 12390 part 8. But no BBA testing involved this proper test.
Pudlo's improvement wasn't greatly different to the improvement others obtained. If Pudlo was added to any of the others' control concretes, it would not be significantly different.
I think Pudlo continued to cheat long after they got a BBA certificate.
Pudlo have had presentation to specifiers slides available on the internet. This image is from that presentation.
They highlight in bold, I added the white circle, a figure a thousand times better than the figure above, which is Caltite. These are the same figures from BBA certificates plotted on the chart above.
This table would allow you to believe that Pudlo is 1,000 times more effective than the product above. Whereas the chart shows you it made a similar tiny improvement comparable with the others.
If you look at the water cement ratio figures to the right of my white circle, the ratio in the control is 0.45, while the ratio in the test was 0.35.
10% less water by weight of cement could not be explained just by adding more cement to the control concrete, because 45% of 350kgs is 157.5 kgs or 157.5 litres of water per cubic metre of concrete.
To reduce the WCR by 10% to 0.35 would require another 100kgs of cement per cubic metre of concrete. Exactly 450kgs.
I have seen Pudlo at a batching plant. The paper bag could easily be held in a hand.
It weighed nothing like 100kgs. Probably about 8kgs.
Significantly reducing the water this much surely means three things.
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They doctored the control concrete before they added their product by reducing the water in it. Cheating.
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The concrete was made with insufficient water to make the 5% gypsum in OPC react first, meaning the concrete had a flash set instead of 2 hours working time. If this concrete was delivered to site it would barely come out of the drum. It would not go through a pump. It would take many more men the same time to spread it, compact it and finish it.
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The grains of cement are not pushed apart at all. Pudlo seem to have managed to compact their test sample and, properly compacted, it would be a very strong and waterproof mix. Which is why they reduced the water in the way they did.
The massive increase in strength is only slightly because of their product. It is mainly because they reduced the water content.
If you think Pudlo is better because you saw this slide, you might now think you were duped.
Some time after I wrote this page, the David Ball Group that includes Pudlo went into administration.
This link opens a press article.
We will have to wait and see whether it reappears, and whether any guarantees will be worth anything.
Incidentally, the slide above shows more clearly than my chart which data Caltite omitted. I think the Caltite admixture made the concrete weaker.
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This link opens the Material Safety Data Sheet for my powerful plasticiser powder.
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