Guild of Project Controls: Compendium | Roles | Assessment | Certifications | Membership

Tips on using this forum..

(1) Explain your problem, don't simply post "This isn't working". What were you doing when you faced the problem? What have you tried to resolve - did you look for a solution using "Search" ? Has it happened just once or several times?

(2) It's also good to get feedback when a solution is found, return to the original post to explain how it was resolved so that more people can also use the results.

HOW TO SHOW CURING OF CONCRETE ACTIVITY

25 replies [Last post]
Kumar I
User offline. Last seen 11 years 23 weeks ago. Offline
Joined: 15 Jul 2003
Posts: 52
Groups: None
IS THERE A MEANS OF SHOWING THE CURING OF CONCRETE ACTIVITY ACCURATELY RELATED TO THE CASTING OF CONCRETE ACTIVITY.

CASTING OF CONCRETE-FS-CURING ACTIVITY (DURATION 7 DAYS),THE SUCESSOR OF THIS ACTIVITY MAY START LATE,BUT THE CURING ACTIVITY HAS TO COMMENCE THE DAY AFTER THE CONCRETE IS CAST AND THE SAME WILL BE DONE FOR 7 DAYS,HOW TO SHOW THIS RELATIONSHIP WITH ACCURATE FLOATS,OTHER THAN USING THE ZERO TOTAL FLOAT CONSTRAINT

Replies

Mike Testro
User offline. Last seen 15 weeks 20 hours ago. Offline
Joined: 14 Dec 2005
Posts: 4409

Hi Kumar

Yhis is the only time that I use a FS link with a lead lag that is set to the approriate number of calendar days.

For a slab you may need to outgoing links - 1. to remove forms say 3 days 2. to remove props say 28 days

Best regards

Mike Testro

Rafael Davila
User offline. Last seen 3 hours 40 min ago. Offline
Joined: 1 Mar 2004
Posts: 5078

Vladimir,

If we have a job in which curing is specified to be done by “Fog Curing” and we have a lot of concrete and a limited amount of Fog Curing equipment then our pours can be limited by the availability of this resource.

Curing is an activity that must start almost immediately after concrete pouring, usually starts before the end of big pours. Therefore, the link between concrete pouring and curing must be a “strong link”.

Take a look at the following schedules:

  1. The first schedule screen is from a sample job before leveling.
  2. The second is from a leveled schedule without using strong links.
  3. The third is from a leveled schedule using strong links. In Spider Project Strong Link option prohibits increasing lag between activities in resource constrained scheduling.

curing 01

I believe this was one of the wishes from our friend David Kelly, a very relevant wish. Spider Project got a solution that yields a workable solution that in occasions can be near optimal or even optimal but in others will not. Seems like a very complicated resource-leveling issue that the more activities you add to the train it becomes exponentially more difficult to solve, maybe a compromise to limit the model to two continuous activities will help to solve most of the issues (a single strong link per activity) very close to optimal.

Although not used frequently "strong links" are very useful functionality when you need it, I would like to see this functionality also on logic links.

Because we do not use fog curing here I do not need to resource load the curing activity, as a matter of fact we use a FS lag for these purposes even when not considered to be a "good practice" by many, here even people out of the construction business know concrete must be cured and need no further explanation for the lag when they look at the schedule. With Spider Project this is even easier as we can define the lag calendar to be Calendar days while preceding and succeeding activities use other calendars of their own while other software complicate such simple thing.

Regards,

Rafael

Rizvan,

I don't know the software that you use but in Spider Project concreting and curing may be delayed only together and thus have the same float.

Best Regards,

Vladimir

Naveen Paladugu
User offline. Last seen 5 years 9 weeks ago. Offline
Joined: 7 Jul 2010
Posts: 47

You can define that activity as a "Level of Effort" activity.

Hussain M Rizwan
User offline. Last seen 5 years 24 weeks ago. Offline
Joined: 30 Oct 2007
Posts: 7

Kumar,

Scenario 1:

For Car park Slab ; there is no superstructure on it . with the curing the activity is completed.

Scenario 2:

For Ground floor Slab; the continuous curing for 7 days must start immediately after concrete casted & wait till ground slab to take load of form works for 1st floor. You will definitely have Zero Float for this.

Scenario 3:

If you make concrete cube sample casted on site & make curing with the structure in actual condition , and you tested the cube in 3 or 4 or 5 or 6 days as proof of sufficient concrete strength was gained at site to stop curing then & go to next activity (which is the best practice specially for precast slabs, still can be used to other areas of concrete )

Scenario 4:

Don't show the curing activity separately just say 'Concrete Casting & Curing' as one activity & make sure successor activity based on this will have lag 7 days. Hope this is very simple Not a Problem of Float.

Rizwan.

Hussain M Rizwan
User offline. Last seen 5 years 24 weeks ago. Offline
Joined: 30 Oct 2007
Posts: 7

Valdimir,

To reinforce my comments check this scenarios;

Scenario 1:

For Car park Slab ; there is no superstructure on it . with the curing the activity is completed.

Scenario 2:

For Ground floor Slab; the continuous curing for 7 days must start immediately after concrete casted & wait till ground slab to take load of form works for 1st floor. You will definitely have Zero Float for this.

Scenario 3:

If you make concrete cube sample casted on site & make curing with the structure in actual condition , and you tested the cube in 3 or 4 or 5 or 6 days as proof of sufficient concrete strength was gained at site to stop curing then & go to next activity (which is the best practice specially for precast slabs, still can be used to other areas of concrete )

Scenario 4:

Don't show the curing activity separately just say 'Concrete Casting & Curing' as one activity & make sure successor activity based on this will have lag 7 days. Hope this is very simple Not a Problem of Float.

Rizwan.

Hi Rizwan,

I have an idea about Concrete Technology & Practice.

Your explanations confirm that concreting and curing activities shall have the same total floats.

Best Regards,

Vladimir

Hussain M Rizwan
User offline. Last seen 5 years 24 weeks ago. Offline
Joined: 30 Oct 2007
Posts: 7

Valdimir,

To understand CASTING OF CONCRETE-FS-CURING ACTIVITY link, you better have an idea about Concrete Technology & Practice.

Technology says; 

After concrete poured in place, it will start setting withing 3 hours of time (initial setting) & finish setting by 10 hours.

you must start curing immediately after initial setting time of concrete finished.

 

Practice is;

If slab this is possible, but for columns & walls its already covered so you can cure only top part which is very small area.

Concrete will gain more than 66% of strength in seven days & 100% of strength in 28 days. As long as the concrete can take (3 to 7 days) enough strength the form work can be removed & the start curing immediately.

So, in case of wall if you say curing for seven days it will consume total 10 days if you wait for striking form works in columns after 3 days. so, leaving form works in column also is one type of curing as it not allowing to dry columns.

So the FS is correct irrelevant to other activities for ASTING OF CONCRETE-FS-CURING ACTIVITY link.

Rizwan.

Kumar,
I don’t know about the existence of this option in Primavera. But this option is extremely useful only when project has limited resources and prevents succeding activity to be delayed without delaying the preceding activity. In case of curing the problem does not exist because curing does not need resources that are limited (if not to use material leveling). Different floats can appear only due to different calendars of casting and curing activities (work hours and vacations are not applicable to curing). So floats may be different but planned start of curing will be scheduled at proper time. If resources are limited planned start and early start may differ.
Regards,
Vladimir
Kumar I
User offline. Last seen 11 years 23 weeks ago. Offline
Joined: 15 Jul 2003
Posts: 52
Groups: None
Vladimir,
I agree with u casting and curing activities should have the same float,it is not necessary for these activities to have zero floats
Kumar I
User offline. Last seen 11 years 23 weeks ago. Offline
Joined: 15 Jul 2003
Posts: 52
Groups: None
Vladimir,
Is there an option in primivera,similar to the option you have mentioned in spider project
Clive Randall
User offline. Last seen 13 years 51 weeks ago. Offline
Joined: 15 Aug 2005
Posts: 744
Groups: None
Kumar
If you really need zero float on curing you need to date constrain and in my mind this flys directly in the face of good planning
Clive
Kumar,
I still don’t understand - if casting activity has float then curing shall have float too, isn’t it? How its float can be zero if the preceding activity has positive float?
In Spider Project there are so called firm (strict) links when preceding and succeding activities are pasted and can be delayed only together. In this case casting and curing will have the same float but it still may be positive.
Regards,
Vladimir
Kumar I
User offline. Last seen 11 years 23 weeks ago. Offline
Joined: 15 Jul 2003
Posts: 52
Groups: None
Hi Friends,

Thanks for your posts and appreciate your efforts.
The Issue is curing activity has to mandatorily start after the concrete has cast and it cannot be delayed ,even if there is float on the sucessor activities like waterprofing,and how to show it in p3
Clive Randall
User offline. Last seen 13 years 51 weeks ago. Offline
Joined: 15 Aug 2005
Posts: 744
Groups: None
Kumar
I am assuming that you have a situation as you outline on a retaining wall. Take the following scenario of a 3 bay wall
Say bay 1 is cast on day 1
Formework which is for this example considered a resource is able to be struck on day 2 under the spec.
Bay 2 formwork erection occurs on day 3
Assuming bay 2 cannot be cast for 3 days after bay 1 due to shrinkage constraints the earliest bay 2 can be cast is day 4
Assuming bay 1 was in the middle then bay 3 can be cast after removal of bay 2 formwork and reerection ie day 7.
Now if you want to do all your waterproofing in 1 go and waterproofing can only proceed after curing the earliest waterproofing can start is day 15 ie cast on day 7 strip on day 8 cure day 8 to day 14.
On this basis bay one would have 14 days of float or 7 days of float on curing and bay 2 would have 10 days of float or 3 on curing. Bay 3 would have no float.
Why do you not get these floats is related to other relationships which affect the backward pass calculation.
I have done the numbers quickly so a day may be in error on some of the floats but it is the principle I am explaining I hope.
I dont see why curing must have zero float and this seems to be unneccassary logic.
If you really want it you must date constrain but thats not planning but manipulation
Hope this helps
Clive
Charles Halwass
User offline. Last seen 5 years 3 weeks ago. Offline
Joined: 12 Oct 2005
Posts: 8
Kumar,

I hope I understand your querry correctly:

P3 is set to Early Start for activities thus curing commences the day after you pour your concrete (in P3). Using FS from pour/cast -> cure -> de-shutter(strip forms) -> waterproofing etc. would give cure the same Total Float as cast/pour (assuming no other influencing links in this sequence) - do you agree with this so far?

Now if deshutter has, say 100days float, then curing will also have at least that much float (depending on how soon you plan to deshutter) So if deshutter starts on Day 8 (7-day cure) then "curing" would also have 100 days float, if there is a delay in de-shutter, then "curing" would have even more float --- correct?

So is your point that: since curing by nature occurs once concrete is mixed/set/poured (unless you freeze it) you want to show it curing with zero float???

If the preceding is a correct interpretation, then I (unfortunately) do not have a great solution to your issue.

However, I don’t agree that this 100 day float on curing is incorrect. Based on the successors, the curing would not technically NEED to finish any differently than the free-float and total-float would indicate in P3. Though, by nature, it would finish much earlier. Also, if you are using early dates in P3 (as most of the world wuold) then your timing for the cure would always be correct as well.

Why do you find it neccessary to show TF=0 on curing? When I have done P3 work on concrete jobs I have usually added an FS lag (1 to 4 weeks depending on concrete strength requirements for successors) after the cast/place activities. If someone wanted to see a curing activity I added one, but we didn’t get hung up on the float. The curing would always be after the pour/cast.

Doing winter concrete work in northern climates at times requires testing with maturity meters or breaking of cast cylinders/cubes to determine when formwork/shuttering, removing shoring supports and loading activities can commence and thus the duration may not be fixed either. I know of one project in Canada where concrete froze in a bridge deck pour. This delayed further activities by months and the curing did not continue until the concrete temperature was raised above 10 degrees centigrade again. I’d sure be glad to have float in that situation.

I’m not sure if this has been any help, but I hope I interpreted your question correctly. Could you explain the importance of showing TF=0 for curing?

Cheers,

Charles H
Kumar I
User offline. Last seen 11 years 23 weeks ago. Offline
Joined: 15 Jul 2003
Posts: 52
Groups: None
Dear Charles,
This is a very valid thread,you check the floats of curing activities in any schedule and u will come to know of the problem,for example the sucessor of curing activity of retaining wall ,may be stripping of formwork,whoose sucessor may be waterproofing and backfilling.

Now curing has to be done immediately after the concrete is cast where as the sucessor of curing like deshutter and water proofing will generally have considerable float,due to which the curing activity will also show an incorrect float! and incorrect late starts

Whats the solution-One is to make the curing activity with zero total float which i want to avoid?Suggest if you have a solution
Charleston-Joseph...
User offline. Last seen 19 weeks 2 days ago. Offline
Joined: 10 Jul 2005
Posts: 1347
Groups: None
Hello,

What kind of thread is this? Kumar, the float should be the same.

How it comes different was due to the logic and network of the succesors activities that you done which we dont have access in the first place.

The onus is with you to make sure that the float should be the same, hence, you need to re-visit what have you done in your logic, predecessor-successor realtionship.

Regards,

Charlie
Casting and curing activities can have different floats due to their different calendars. Why does it matter?
Curing activity can be defined as dependency lag but in this case it will not be seen and besides curing may need heating and thus resources (electricity in particular) may be assigned.
pmkb .
User offline. Last seen 10 years 27 weeks ago. Offline
Joined: 15 Sep 2005
Posts: 79
Groups: None
If casting and curing have a FS relationship, they should have the same float. The only two possibilities which could cause the float to differ are:
  • a disjoint between working calendars (ie. between the casting task and the curing task’s successor - assuming that curing is a 24 hour calendar)
  • the casting task has some other successors with a lessor float path than the curing task
Either way, I really don’t see what the problem is. The early start, early finish and float should all be calculated correctly given the defined parameters. Any additional hours on the curing task’s float (beyond the casting task’s float) should not impact the critical path should the casting task be delayed to it’s late start.

Stacy
Project Management Knowledge Base
Kumar I
User offline. Last seen 11 years 23 weeks ago. Offline
Joined: 15 Jul 2003
Posts: 52
Groups: None
Mr Clive,

The curing activity has to start say 1 day after the concrete is poured mandatorily,hence the late start of this activity cannot be displayed in relation to its sucessor

The float of the curing activity and concrete casting activity should be the same
Trevor Rabey
User offline. Last seen 2 years 20 weeks ago. Offline
Joined: 29 Nov 2005
Posts: 528
Groups: None
The time for concrete to cure (or paint to dry or fibreglass to go off) is not an activity/task at all because it is not something which someone or something has to do, is it? It is the time between the end of pouring concrete and the earliest that we can begin to strip formwork. It’s lag on the FS link between pouring and stripping.
Clive Randall
User offline. Last seen 13 years 51 weeks ago. Offline
Joined: 15 Aug 2005
Posts: 744
Groups: None
Kumar
Does it matter and if so why
The earlist date is 7 days after casting the latest is whatever you have linked it to say strike falsework etc.
I cant see the issue here
Clive
Kumar I
User offline. Last seen 11 years 23 weeks ago. Offline
Joined: 15 Jul 2003
Posts: 52
Groups: None
The Relatioship below is ok.Curing of concrete should have the same float as casting of concrete activity,but in p3 this is difficult to show correctly,as the float of the curing activity is incorrectly displayed at it takes the float of its sucessor activity ,as the sucessor of this activity can start late,but the curing activity has to mandatorily start after the concrete is cast
Kumar,
I don’t understand what is wrong with CASTING OF CONCRETE-FS-CURING ACTIVITY link?