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I thoroughly researched how to waterproof concrete throughout 2012.
Since then I have been very public criticising admixture manufacturers for not being as honest as they make out.
I could be out of date now, but no one has contacted me in any way to say that they have improved anything - so I don't expect that I am out of date.
How to Waterproof Concrete. Science Lessons.
How the science evolved.
Two or three decades ago, Japan spent a fortune trying to keep their economy moving by building huge infrastructure projects. Some years later many repairs were needed to the concrete. It turned out the labourers had been reluctant to do the heavy work vibrating the concrete properly so some concrete was poorly compacted, and that is what failed.
Academics looked for a way to make vibrating unnecessary.
Plasticisers were generally waste lignin from wood processed to make paper. Incredibly cheap with some electrostatic repulsion. Electrostatic repulsion is what makes two magnets the same polarity repel. The liquid in the wet concrete repelled itself and flowed better.
Super-plasticisers work the same way. They are mostly naphtha based which means they are made from crude oil. Deliberately manufactured. Cost more. Better. But still it is only the liquid repelling the liquid.
The Japanese academics came up with a much longer, far more effective molecule with more electrostatic repulsion; and they found a way to stick this molecule to a solid. It was better because neighbouring solids repel neighbouring solids. Solids slide past each other much better.
Polycarboxylate Ethers (PCEs).
The Japanese found that they could make what they call High-Performance Concrete very easily with PCE. PCE is what makes self-compacting concrete possible.
If the same C40 concrete mix is used with PCE instead of Naphtha super plasticiser, the mix will
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Be more workable, cohesive, denser and stronger.
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Therefore the same strength can be achieved with less cement.
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Or waterproof concrete can be achieved with PCE, more cement and less water.
Throughout Japan, Korea and China most concrete is made with PCE to reduce the amount of compaction needed and to make concrete with less cement.
The evidence.
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.
By 1988 no one had created the plasticiser that would make concrete delivered to construction sites sufficiently workable at 0.50 water to cement.
Traditional plasticisers work by separating cement particles from flocculation with electrostatic repulsion.
However the Japanese developed polycarboxylic ether polymer chains (PCEs) during the nineties.
The backbone side of a PCE gets adsorbed while the side chains on the other side can have chosen chemicals added to them for a variety of benefits, not just for concrete. PCEs are used in textiles, printing, paint and cosmetics as well as concrete, depending on what useful chemical is added to the backbone molecule.
The Japanese invented a way to stick water reducing plasticiser on to cement grains, instead of the plasticiser moving around in the water. This increased effectiveness by many times.
See Advanced Concrete Technology by Professor Zongjin Li, page 71 (2011), Wiley: New Jersey, for more explanation.
This means completely waterproof concrete has been produced in Japan since the nineties.
But this knowledge did not find its way into UK text books for about 15 years.
2011: "concrete with a low water/cement ratio ... make the capillaries discontinuous ... water would not be able to enter the interior of the concrete"
On the same page, under the heading Autogenous Healing "Fine cracks in fractured concrete, if allowed to close without tangential displacement, will heal completely"
Neville, A.M. (2011). Properties of Concrete. 5th ed, p330. Harlow: Pearson Education.
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