Type G admixtures
Posted by Frank from Abu Dhabi, OT, AE on March 25, 2007
Bruce,
We have a mix design using type G admixture to improve the slump/workability and retardation of settting time for marine piling works (ie barged concrete). Is it acceptable to redose on site with the same Type G admixture to increase not only the slump but the time allowed for placing even though the specifications require a maximum time of 1.5 hours?
A Type G admixture can be used for re-dosing in specific cases. The factors influencing would be the amount of admixture added while re-dosing, the slump of concrete before re-dosing and target slump. Re-dosing will cause retardation, the extent of retardation would depend on the ambient temperature. At higher temperatures re-dosing will have less influence on retardation.
I would advice you to contact the admixture company from whom you are buying the admixture, provide him the mix design details and ask their opinion about this matter.
If the purpose of re-dosing is just to increase the slump and you are not looking for a longer slump retention, the best option would be to re-dose using a Type F admixture.
