Date: January 1, 2010

News - Adding Water to Concrete on the Jobsite

Water can be added on site if some of the water from the mix design was held back during the initial mixing. Otherwise, if additional water in excess of the design mix is added, the purchaser assumes responsibility for the resulting concrete quality. The alternative of using a water-reducing admixture or superplasticizer to increase concrete slump should always be considered because adding to much water may weaken the concrete or cause cracking.
  • Before concrete is discharged, the slump of the concrete should be determined using a sample from the first ¼ cubic yard of concrete that is discharged.  
  • When water is added at the jobsite, it should be added to the entire batch. 
  • Adding one gallon of water per cubic yard increases the slump by one inch, decreases compressive strength 150 to 200 psi, wastes about ¼  bag of cement, and increases shrinkage by 10%.
  • Measure and record all water added on the jobsite.
  • Mixer drum should mix in the water with 30 additional revolutions at mixing speed, or 10 revolutions at 20 revolutions per minute.
  • After more than small portion of the concrete is discharged, do not add any more water.

Other news articles from January 2010