Adding more water

Effects of 10 more litres to a cubic metre

We often get customers who insist we add more water to the concrete on site, so before we do we advise them on it and if they insist we get them to sign for more water.

If you ask the driver to add 10 more litres of water to a cubic metre of properly designed concrete: 

  • you increase the slump by about 20mm
  • you reduce the compressive strength by as much as 3 N/mm2
  • you waster the effect of 15 kg of cement per cubic metre
  • you increase the shrinkage potential about 10 percent
  • you increase the possiblity of seepage through the concrete by up to 50 per cent
  • you decrease the freeze thaw resistance by up to 20 per cent
  • you decrease the resistance to attack by de-icing salt