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self build basement concrete waterproof self build basement formwork shuttering wall form self build basement drainage membrane self build basement concrete waterproof consultancy self build basement concrete waterproof supervision training
Concrete additives to make your work easier and better Formwork accessories to make your results waterproof and flat Budget external drainage membrane Consultancy and advice On site supervision and training

 


Admixtures for concrete.

We can sell you an admixture that makes concrete waterproof.

As good as any of the rest out there.

For less money.
£23 a m³. If we come to you, train and supervise, and you buy all other relevant products and services from us, I will personally guarantee your structure will not visibly leak. Concrete or joints.

This is absolutely unique. I will guarantee your workmanship if your team did everything my way.

We don't go into the science here. You can read all the science on this discussion web site www.waterproofconcrete.co.uk.
 


Concrete can be made a million different ways for different advantages.

This concrete is absolutely waterproof.

But it goes stiff quickly.

You cannot get a perfect finish on this concrete

Unless
easy float slab nut leveller
  1. You are very experienced with this concrete, and

  2. You bought our slab levelling kit so that you spend very little time raking concrete around before you can try and get a float finish, and

  3. You get your concrete placed by an overhead boom pump, not by a line pump, and

  4. You have 5 hard working guys.
overhead boom pump


This page is in 5 parts Click on these links to go straight to the part you want to read.

waterproof readymix concrete  
  1. £23 a m³. You buy it and put the powder in yourself.

  2. £23 a m³, £300 a day and rods, nuts, poker hire as appropriate.
    We come to you, supervise and guarantee your workmanship.
 
  1. Mixing concrete on site and making it waterproof.

    Liquid admixture £5 a m³
  waterproof readymix concrete  

basement concrete pump over house  
  1. Pump-Save Retarder.

    You need this to get good joints between different loads of concrete.

    Each dose to add to the last 0.5m³, £4.50. To avoid problems like this.
  concrete leaks

slab levelling nut  
  1. Slab levelling System.

    You resin fix our fibreglass rods vertically into holes you drill into your concrete blinding.

    Use the rods with nuts or rails.
    Nuts cost more but they are far easier and quicker.

    Rods are £7 for 2m. Nuts are £2.20 each.
  slab levelling rails


All prices subject to delivery cost and VAT.


Powder to make drum-delivered readymix concrete* waterproof -
    Added by you.

Making readymix delivered in large trucks waterproof yourself.

* The concrete purchased must be the mix we prescribe.
P350
CEM 1
over sanded for pumping
You want to order 60mm slump if you add the product on site.
   120mm slump if you give the additive to the concrete supplier to add at their plant.

no other additives

Tell your readymix supplier that you will be adding and mixing in your own super plasticiser when the concrete arrives.
If you are asked, don't open a can of worms about Health and Safety unnecessarily. The plasticiser will be put in for you by the pump operator who will toss the sachets in from the back of his pump truck, without standing on, climbing up or even touching the concrete truck.

Let them know that it is a very powerful plasticiser so they should only put in the water for 60mm slump - less than usual.

Most important. Mix the powder in 6 revolutions per cubic metre. Any less and the powder won't be thoroughly mixed and the pump will block when it pumps any concrete with too much powder. The clean up or repair bill will be several thousand pounds. YOU MUST COUNT EVERY REVOLUTION YOURSELF. YOU CANNOT TRUST ANYONE ELSE TO MAKE SURE THE POWDER IS PROPERLY MIXED. ESPECIALLY NOT THE TRUCK DRIVER OR THE PUMP OPERATOR.

If the concrete is still dry with the additive in add water cautiously. Only 5 litres at a time.

Be quick with everything. The concrete will start stiffening quickly.

Very occasionally, and usually only in hot weather, if you have had to add more than 20 litres of water and the concrete is still stiff, the batching plant put in way too little water and the concrete is setting prematurely. You have to find and put in water in 50 litre doses as fast as you can. Use the concrete as fast as you can. Try to find somewhere less important for this load, such as the bottom of the slab

If you haven't bought Pump Save Retarder, tell the pump man to keep an eye on things if there is a delay between trucks. But don't let him think it will set solid in his pump. It is still just concrete, it might stiffen quickly, and he might have to do an extra washout (wasting £25 of your concrete) but it won't make crystals of concrete for hours. Keep your slab wet well into the evening to prevent it drying out too quickly.


If you buy the sachets of powder to put in yourself, you need to know that each sachet is sufficient for 2 cubic metres of concrete.

When the driver complains about cost of diesel, look him straight in the eye and tell him you have paid for mixing. Tell him to mix it or take it away.

You should not be persuaded to add any more water to make the concrete runnier because then you will lose essential grout out of gaps in your formwork and the concrete won't be waterproof. You need all the sand and cement to get the required density. (Don't worry about a thin dribble, but worry about losing half a shovel full.)

Click here to open the Material Safety Data Sheet for this powder.


The admixture for readymix concrete can only go in drum trucks that carry concrete batched back at the batching plant. I cannot waterproof volumetric mixer concrete. Neither can anyone else unless they got a truck specially adapted to suit a particular chemical.

waterproof readymix concrete


Powder to make drum-delivered readymix concrete* waterproof.
    Added by me when I come to supervise.

We come to you, we put the admixture in the concrete*, we supervise your team as best we can.

Price £23 per m³ to treat the concrete. £300 for the supervision visit**.

For a little more money we will guarantee your workmanship won't leak as well.
  1. Buy our rods and nuts, as appropriate, rather than anyone else's. Ours are waterproof.

  2. Rent our pokers rather than anyone else's. We know ours are powerful.

  3. Form joints and walls as we explain on various web pages.
concrete waterproof powder
£23 per m³ is about half the price of other admixtures but our service is a 100 times better because we guarantee your workmanship if you followed our advice. No one else does, they only guarantee their chemical to the value of their chemical - even if they attend site and watch.

They would also get you to spend a lot of money on something to go in the joints. If your workmanship is bad these extras don't work anyway. If your workmanship is good you don't need them. So listening to us and doing as we say will save you money as well as avoid leaks.

Making readymix delivered in large trucks waterproof.


* The concrete purchased must be the mix we prescribe.
P350
CEM 1
over sanded for pumping
target slump before additive 60mm
no other additives

Tell your readymix supplier that you will be adding and mixing in your own super plasticiser when the concrete arrives.
If you are asked, don't open a can of worms about Health and Safety unnecessarily. The plasticiser will be put in for you by the pump operator who will toss the sachets in from the back of his pump truck, without standing on, climbing up or even touching the concrete truck.

** Subject to minimum amounts per visit, depending on travel distance. Give us a call, number at the bottom of this page.

We have lots of other information on our basement building web site:
Basement Expert Ltd

It is the concrete that will be waterproof, not the admixture. As such a BBA product certificate is not appropriate and we do not have one. However we have had many successful tests for water permeability under pressure.

Many, many large sites routinely test concrete for strength to BS EN 12390 part 3.

We get concrete tested to BS EN 12390 part 8 as well. Depth of penetration of water under pressure on concrete. The pressure is equivalent to a depth under water of 30m and the pressure is maintained for 96 hours.

Click on either image to the left to see two original test certificates.
  concrete compressive strength report to BS EN 12390 3 concrete permeability report to BS EN 12390 8


I have included here a photo extract from "Advanced Concrete Technology, volume called Processes", Chapter called "Concrete construction for liquid-retaining structures" by Tony Threlfall, 2003, Butterworth-Heinemann. Page 16.2.

It says that any result better than 50mm is good. You will see on the certificate for impermeability that our results in this case were 1, 1 and 3mm. We have dozens of similar results going back years, so we tend not to pay for this test (£600 plus VAT) any more.
  Click on this image to be able to read the text from the book.   from Processes, water retaining BS EN 12390 8


I will not be persuaded to add any more water to make the concrete runnier because then you will lose essential grout out of gaps in your formwork and the concrete won't be waterproof. You need all the sand and cement to get the required density. (Don't worry about a thin dribble, but worry about losing half a shovel full.)

Click here to open the Material Safety Data Sheet for this powder.


The admixture for readymix concrete can only go in drum trucks that carry concrete batched back at the batching plant. I cannot waterproof volumetric mixer concrete. Neither can anyone else unless they got a truck specially adapted to suit a particular chemical.

waterproof readymix concrete



Mixing concrete on site and making it waterproof.
£10 for enough additive to make at least 1m³ of concrete on site. You will be supplied with a measure with your order.

mixing waterproof concrete on site

You will need to make some gauges. I use two buckets for the ballast and a pot for the sharp sand. I cut bags of cement in half with a hand saw.

A typical batch will be
30 litres of ballast
2 litres of sharp sand
half a bag of cement
start with 2 litres of water
correct dose of liquid admixture purchase.

You will get instructions and a measure with your liquid admixture.

Add more water very slowly until the concrete flows, but is not runny, in the mixer.


Mixing concrete by hand is very expensive compared to full loads of readymix. You should probably only mix by hand where readymix would be too much at once unless you paid a lot extra for a small delivery or extra time on site.

There is no need to buy retarder for hand mixed concrete.

Wash the mixer every hour so that it is easy to keep clean.

Click here to open the Material Safety Data Sheet for this liquid.




Pump-Save Retarder. £4.50 a dose.

We could have called it "Cold Joint Preventer" instead. But getting soild concrete out of a pump pipe is worse than chiselling out a joint and refilling it. So it is called Pump-Save Retarder even though it prevents cold joints as well.


Concrete is the result of water and cement being mixed. After about 2 hours water merges with the surface of the cement grains and the mix becomes very stiff. Some hours later the merged parts form gel and by the evening crystals are forming from the gel, releasing excess water to merge with more cement, and so on.

Waterproof concrete has more cement and less water than usual, so it gets to the stage where it is too stiff to move sooner.

The concrete arrives stiff. The admixture is mixed in and the concrete flows. The pump hopper gets filled and the concrete is pumped until the truck is empty. When the delivery truck pulls away it leaves the hopper and the pipes to the top full of concrete - that sets where it is if it is there long enough.

readymix concrete 60mm slump   concrete waterproof powder   waterproof concrete sits in the hopper   concrete sits in the pump pipes

Concrete setting in pipes takes a lot of getting out. The extra bits of line can be cleaned with a jet washer and rodding them with steel. It might take an hour but they can be cleaned. But to clean the pipes up in the air they have to be taken off back at the yard and the concrete pushed out with a hydraulic ram. This takes a couple of days so the penalty charge is big.

If the pump is completely bunged up and more concrete arrives, you will have to pay for that concrete but send it back because you cannot pump it. That means you will have to pay up to twice as much again for its disposal.

It doesn't usually get to that. But somewhere in between is common. If the concrete in the pump had the water added back at the plant more than 2 hours before the next truck arrives, it will probably pump out. But it won't compact. And where it won't compact it will leak.

waterproof concrete set stiff in pipe   set concrete from the pipe   leaking cold joint   concrete leaks

Concrete does not arrive two hours old and you can usually get most of the concrete in and compacted with time to spare. It is the last half cubic metre or so that sits in the pump's hopper and throughout its pipe system that sometimes gets to be two hours old before new concrete arrives and pushes it through.

So it all depends on when the next truck arrives - and that is out of your control.


But I hear you say, "if this is so common why haven't I heard about this before?" Because in the real world the pump operator or the workforce add water to the concrete in the pump hopper and circulate it through the pipes as soon as they realise there is a delay. In that way they keep the concrete liquid and they get good looking joints without blocking the pipes.

But extra water pushes the grains of cement further apart. Google 'effects of too much water in concrete' for yourself and these are what you will find.
  • The concrete cannot become waterproof. Instead it will be porous.

  • More water makes the concrete weaker.

  • After a few years the concrete will crack (so presumably leak).

  • The concrete could segregate. That means the stones and the cement end up in different places and the stones have no glue.
These are problems no one can see while the workforce is still on site. The concrete will look fine for several months at least.

But if it is going to be your basement, or if you will sell it with a 10 year guarantee, you will be responsible for poor workmanship, not your insurer.



The simple solution is to add a sachet of Pump-Save Retarder to the last half cubic metre of concrete in the delivery truck to give that concrete another couple of hours or so before it begins to set. With no harm to the concrete at all.

Keep tapping the drum and when there is about half a cubic metre left inside it, stop the discharge, toss in a bag of retarder and mix it 6 revolutions.

Carry on using the concrete. If you timed the retarder just right the concrete left in the pump will not go stiff for another couple of hours at least.

Important note. The retarder can only work if the concrete is still runny. If you are discharging the concrete very slowly you might need to retard much more concrete. In average weather add the retarder after less than 2 hours from when the concrete was batched. Sooner in hot weather.

It might be wise to buy twice as many doses as truck deliveries you expect, so that you have some spare doses in case one load is being discharged very slowly and you need to retard a lot more than half a cubic metre.



Please don't be afraid of paying me to attend your site when you concrete. Experienced people are not experienced at using concrete that is really quite different, because they have much less time than they are used to. Inexperienced people get it all wrong. Save money later by making me responsible for any leaks - and I will make sure you don't have any.

This is a very recent job where they thought they could do it without me. They have leaks everywhere. Not through the concrete but through all the gaps and bad joints.

concrete leaks


It should not look like that, it should look like this. The difference is only that I was there supervising.

waterproof basement



Slab Levelling Systems.

Two purposes.
  1. The more visual guide you have, the more accurately you can place concrete with just the right amount everywhere, reducing the amount of concrete you need to rake around.

  2. The more guides you have the flatter you can float your concrete.
If your concrete is not level
  • You will walking through puddles while you build your walls and everyone will be miserable.

  • You will have some added expense overcoming the undulations with your screed and you might lose some headroom in your finished basement.
 
simple screed rails result


What's happening in this photo looks all very well until you understand all the issues with it.
  1. The scaffold pole is 50mm diameter, so it exceeds the 40mm cover specified by the engineer. There is an element of cheating and not following the design is your responsibility not your engineer's.

  2. Support stools would not go through the steel. So although it looks like it will be a smooth finish, it won't be a level finish because the poles are tied to the steel.
    Where the steel is high the concrete will be high. Where the steel is low the concrete will be low.

  3. As the work continues, someone will have to walk through finished concrete to cut the tying wire and remove the poles.
  slab level scaffold
A much easier and better system for a basement slab costs £7 for a 2m rod that you cut into several lengths and whole nuts £2.20 each.

A basement floor slab always gets covered in insulation and screed because building regulations say so. Therefore you want it flat and level. It does not need to be a pretty finish.

slab levelling stool   Two problems with chairs for scaffold tubes
  1. They don't go in between all the rebars all the time. They won't go through spacing less than their size and they won't go through where mesh overlaps. Neither will they go through where the top mat isn't exactly over the bottom mat.

  2. Secondly a scaffold tube is 50mm diameter and the concrete cover is usually only 40mm.


We recently invented the simple solution that will also always be waterproof. A fibreglass rod with a nut on top to adjust accurately to the required concrete level.

You have the choice of the top of the nut being top of concrete, so the nut will be cast in and sacrificed.
Or adjusting it so that the bottom of the nut is top of concrete. You can rescue the nut and cut off the last bit of rod in the morning.

The rod might be an offcut if you used our products before.
  nut leveller


18mm diameter threaded rods made with fibreglass. You only need to get a long drill bit through the steel.

The simplest, fastest method is to cut rod to length and resin fix it in a hole you drilled. Sometimes offcuts from a previous wall form will do.

Whole nuts cost £2.20 each. You screw them on till they are at concrete level.


We tried a number of variations. In trials, numerous rods with adjustable nuts on top were by far the quickest to install and most popular with the concreting gang.

They did not like the timber batten because it floated and curved up. How thick the rails can be is determined by your cover. If your top cover over your steel is 40mm you probably have to use a rail only 30mm thick.

slab levelling rails

If you want rods cut to a particular length and slots cut into one end, and you want nuts cut into thin nuts, guide prices are at the end of these instructions.

  • Accurate

  • Cheaper

  • No Mess

  • No Fuss

  • No Injuries

  • No Work Done Twice

  • No Puddles

  • Workers Happier

  • Satisfied Client
  The best Process we found to create lines of rails. Youtube video here.
  1. Drill holes about 2m apart in lines across the slab.

  2. If you can drill right through the blinding you can often tap the rods down so the tops are "Top of Concrete". Otherwise cut a bit off the bottom of the rod first as required.

  3. You can fix the rods with a little squirt of resin.

  4. Screw a thin nut on to each rod.

  5. Measure between rods and cut 2x2 a few mms shorter.

  6. Tap in a 40mm nail one end at the bottom and the other end in the middle.

  7. Fit the rod first where the pour will start, with the lower nail at the edge of the slab.

  8. Continue across the slab then continue each line.

  9. Wind up the thin nuts so that the top of rail is "Top of Concrete". You can see that it is the thin nut that is taking the weight of the rail. The nails just keep them located.

  10. When you have the rails in place you can squirt a little bit of resin into the slot so that the nails get glued in and the thin nut can't turn.

  11. As you concrete and finish the surface with your screed bar, you can yank out the 2x2 from the edge of the concrete thus far, bending the nail and leaving it behind. Then you can pull the far end of the 2x2 off the nail at the far end and carry the wood away - easily.

  12. Finally, mix up some sharp sand and cement and fill the voids left by the 2x2 after the slab can be walked on and before it gets dirty.
 

slab levelling drilling

slab levelling slits

  slab levelling resin   slab levelling done   slab levelling slits 2


One slab levelling kit comprises 1 rod with a slot cut at one end and 1 thin nut.
You fix 2 rods into your screed,
measure the distance between them,
cut 2x2 to suit and put a 40mm nail in each end,
use the thin nuts to bring the top of the screed rail to finished concrete level,
you can glue the nails and the thin nut to the rod with a drip of resin glue.
As soon as the rail is finished with, rip out the end nearest you then pull it off the far end.
Dead simple.

Flush sets have rods 400mm long.

Visible sets have rods 600mm long and longer slots.

Prices
Flush sets £2.38 each plus delivery and VAT.
Visible sets £2.79 each plus delivery and VAT.
  Just a suggestion

Screwfix code for the quick-setting resin we use

Rawlplug-R-Ker code 85750








Phil Sacre:

01438 900303




07773 377087





Email me:

philsacre@basementexpert.co.uk

 

self build basement concrete waterproof self build basement formwork shuttering wall form self build basement drainage membrane self build basement concrete waterproof consultancy self build basement concrete waterproof supervision training
Concrete additives to make your work easier and better Formwork accessories to make your results waterproof and flat Budget external drainage membrane Consultancy and advice On site supervision and training
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SELF BUILD MY BASEMENT

Case studies