There is more than one way to account for modeling concrete cure time in Primavera P6 Enterprise Project Portfolio Management (EPPM). Let’s look at how to create a schedule in Primavera P6 EPPM that models cure time as a separate task.
In the precedence diagram lag is the waiting time between a predecessor and successor activity. One common lag application is to model the cure time of concrete as a positive lag. This concrete cure lag is unique because concrete cures 24-7.
Primavera P6 EPPM has the functionality to assign this cure time lag a 24-hour calendar. Modeling concrete cure time this way, is effective to continue the concrete curing process through the weekend non-work days. The one negative of this approach is that lag is not very transparent. The concrete cure lag appears on the Gantt chart as a simple line and having no explanation as to the actual process. This has led schedulers to model the concrete cure time as an actual task, which is more transparent than lag.
This article demonstrates modeling concrete cure time in Primavera P6 EPPM release 16.1, as an actual task.
Primavera P6 EPPM and Modeling Concrete Cure Time as a Task
First, this demonstration uses the classic view in Primavera P6 EPPM release 16.1 to create and analyze our concrete cure schedule. We have our demonstration schedule in Figure 1.
Figure 1
This schedule has a positive lag between pour concrete and strike forms to model the curing of concrete process. This schedule uses a 24-hour calendar to schedule relational lag, which works well to model the curing of concrete during the weekend days. The negative of this approach is its lack of candor; it is not very transparent.
To more clearly describe the concrete curing process the concrete cure is modeled as a unique task, Figure 2.
Figure 2
In our demonstration the concrete cure planned duration is 5-days, but the concrete cure process continues for 7-days. This is because our standard 5×8 calendar does not account for weekend cure time. We need to update the calendar for the concrete cure task. To do this select Administer | Enterprise Data, Figure 3.
Figure 3
In Figure 4 we define a ‘7-Day Week Cure Time’ calendar.
Figure 4
Note the everyday Sunday through Saturday is an eight hour work day. This way we can log a full day’s curing on each of the weekend days, Saturday and Sunday.
In Figure 5 we assign the concrete cure task a ‘7-Day Week Cure Time’ calendar.
Figure 5
The updated schedule computes as displayed in Figure 6.
Figure 6
Concrete cure is a five day activity that includes weekend activity. Great! Everything looks good. And we have a more transparent schedule. But this method of modeling cure time is not without issues. Watch what happens when the concrete curing concludes on Friday, Figure 7.
Figure 7
We lose our critical path, because activities upstream of strike forms now have 2-days total float, Figure 7, indicating they can delay the two days and still not impact project completion. This is not good! We have lost the map of our critical path that tells us which activities to compress to optimize the schedule. How do we regain our critical path?
In resolving this issue we have two alternatives. We have two ways to update the definition of critical activities. The first way is to define critical activities as 16-hours total float or less. This way any activity that has 2-days total float or less is flagged as critical. This works to include our two weekend days on the critical path. But it runs into issues when Monday is a holiday.
Another preferable approach is to define critical activities as longest path. This way all activities that rest along the longest path through the network are logged as critical. In Figure 8 we choose to define critical activities as longest path.
Figure 8
And as displayed in Figure 9 we again have a continuous critical path through the network of activities.
Figure 9
We also have achieved more clarity in our true project situation.
Summary
To improve schedule transparency in Primavera P6, model a concrete curing process as a task that has a unique 7-day workweek calendar. This technique works well to include the weekends in the curing process. There are always issues when the curing of concrete concludes on Friday.
This generates 2-days total float on activities upstream of the strike forms effort, and we lose our continuous critical path. But defining critical activities as longest path restores the one unbroken critical path through the network, which is helpful to have for P6 schedule optimization efforts.