Correct calendar for curing time

Hi Mike, I don’t work in the building industry (high rise) where I would expect concrete curing times are of more significance than in general plant construction. In most cases I am scheduling at the master schedule level where the activity ’install concrete’ generally implies detail earthwork, formwork, rheo, pour, cure & clean-up for, say, a typical slab foundation on which to set structural steel and I am not concerned that this duration may in fact include some ’fat’ during curing because of the effect of weekends/holidays. Can you not live with the use of the same calendar for curing as the reaminder and the possible bit of ’float’ which weekends/holidays may cause?

cheers,

Omar

Mike,

In these circumstances, does it not just generate extra free float for the Curing Activity, leaving the total float unmolested? Have just tried to replicate and that’s what happened to me.

Hi Gordon

No the total float is changed.

So in a simple cascade of:

Pour slab > Cure Concrete > strike forms and the cure concrete (24/7) lands in a holiday period then anything upstream of the pour slab activity drops off the critical path and does not appear in any filter.

It may not be much of a problem for construction planning but its a real nuisance in delay analysis.

Best regards

Mike Testro

Hi Mike,

Have you tried setting the critical path to being the longest path, rather than one with zero float?

I have had similar problems particularly where some activities are on a six day calendar and others on five day. I have had to dig out the real crtical path manually (not too difficult as you can generally filter on "Float <7" say and trace the logic back) then have a code field called critical to filter on.

I hope this helps
Adrian

Dear Mike,

Can you assume that whatever the calender number of hours were, the calender day is what you really want to count.

The curing will progress at the same rate. It depends on the spans and the concrete test cube results at 7 days. You do not have to wait the whole 28days.

Should the end of the curing period fall within a holiday, when the deshuttering activity should start, then it depends on the manpower available at site and that is governed by the work calendar that you have.

I hope that my answer helped in some way.

Best Regards,

Samer

Mike,

In these specific circumstances, would it not be appropriate to ascertain the minimum DOWNSTREAM float (to be honest that’s all I checked in my little mock up) and apply a corrective constraint to the start of the curing activity to transfer the smallest total float value to the predecessors of the curing activity (essentially bridging the activity). Not sure what the legal standing of these adjustments would be, but I’m sure they could be suitably substantiated.

Hi Gordon

In delay analysis the first thing to do is take out all constraints - including ALAP.

I have been doing a bit more research myself and I think I may have cracked it - only works in PowerProject though.

1. Set up the curing period with a lead lag link between pour and strike set to calendar days - not work days.

2. Add a buffer task between pour and stike and set to 24/7 calendar.

3. The buffer will fill the gap between pour and strike accross holidays and maintain the critical path.

Thanks everyone for your input.

Best regards

Mike Testro