Hi I am working on a project involving pipe supports on new R.C pads. The anchors in the attached designed are to be cast in a new recently poured pad. Our client needs to drill and fix them as soon after casting as possible. What is the minimum time after pouring is drilling and setting permissible please?
Thank you for your enquiry. Whilst the design undertaken in the Profis Engineering software would be based upon the modelled concrete strength being attained onsite prior to the load being applied. That being said we have previously carried out internal testing regarding this subject. The conclusion from the testing is that the drop in resistance is coincident to the reductions identified within EC2 for early age concrete. Note that the cement used in the concrete mix has a significant influence before the 28days and as such the reductions shall be observed.
As practical rules please consider the following:
1) Before the concrete reaches 3 days of curing it is not advisable to install the anchors since the scatter for the concrete resistance is to high.
2) From day 3 to day 20 a reduction should be applied considering the values presented according to the EC2 expressions for early age concrete.
3) After day 20 the reductions are minimal regardless of the cement class and as such no special reductions need to be applied.