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Hello, I'm working on a simple plan for an office building. it's some how decided that project life time is double concrete work life time. so, what I'm looking for is productivity rates regarding to concrete work as well as Method Statement for Concrete Work (Foundation, Slabs, Columns, etc....) something to tell me what is my limits instead of putting 140 workers to finish 5000 sqm slab in 10 days.
Regards,
Ahmad Abdrabou.
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good advises, thank you Mike
be safe.
Hi Ahmed
With a deep excavation you need to consider the method of support for the excavation.
It is essential that you talk to the construction team because there are many methods depending on the site circumstances.
For instance if there is plenty of space around then the cheapest method is to batter and backfill.
If there is very little space then you need some support system in place.
This could be temporary using steel sheet piles or permanent using contigous piling or sheet steel and ground anchors.
Don't forget to check for underground services that may be in the way.
Dewatering is only a problem if the excavation is unsupported or in particularly unstable ground. It is usually best covered with sumps and powerful pumps. Other methods such as a ring and and wash down pumps would not be suitable for such a large basement - nether would freezing or solidifying gel.
The excavation may have to be in two stages using walings and cross beams - depending on the engineering design.
I cant tell you about this - you must study the drawing and ask someone who knows more about the job.
The problem with a 1.4m thick slab is the heat generated by the curing process will crack the salb if it is poured in one go - so it is best not to pour it in one layer - 3 layers would be better and again in checquer pattern with the layers over lapping.
If the retaining walls are insitu concrete then they may be an integral part of the slab.
The back earthwork support may be used as permanent formwork or it may need a backform.
Again the walls must come up in levels to suit basement upper slabs which are the same sequence as the upper floors.
Waterproffing can be any sort of membrane or none at all where ground water trickles down behing the retaining wall and is taken away by a gravel drain. Again you need to check what system is required.
Finally whenever I am faced with something that I do not know I ask someone who does. There is no such thing as a stupid question - which is why I am trying to help you now.
Best regards
Mike Testro
Dear Mike, thanks to you my mind is pretty well organized for superstructure concrete work.
Now for the substructure, from what I see the plan as follows:
-Site levelling and grading
-Excavation
-Dewatering (I know nothing about it)
-Backfilling and compaction
-Plain concrete 1st layer
-Waterproofing
-Plain concrete 2nd layer
-Reinforced concrete / Foundation (massive one, the foundation hieght is 1.4 mt)
-Basement concrete work (does it differe from superstructure floor work?)
-Water protection for basement external walls
-Backfilling arround the main building (do I have to finish it before superstructure work?)
END OF SUBSTRUCTURE WORK
Still one item is missing which is Retaining walls, I don't know about this either, where to start & where to finish.
I'd appreciate if you confirm / modify this sequence of substructure work with explaining in brief for questions.
Regards,
Ahmad.
Hi Ahmad
I would not reccomend pouring a 5,000m2 slab in one pour as it will cause shrinkage cracks I would suggest 8 bays about 25m2 laid checquer pattern and then you can pour the whole slab in 2 days. 1000m3 a day is achievable with a pumped pour. You will need extra time for the bay formwork.
You should be able to work on the slab the next day.
Best regards
Mike T.
Hey Mike,
Thanks a lot for your reply, very profissional.
about missing information:
- the building is designed to be made of a slab foundation, 2 basements and 6 floors, basement area is 8000 sqm, floor area is 5000 sqm. Also it shall has 2 expansion joints.
I made a small plan for the repeated floors, based on the activity sequence you mentioned and the quantities i've, productivity as well, and came up with 40 working days for floor without inspection time. Is that reasonable for 5000 sqm slab? do I've to divide the work according to expansion joints? best senario is to work the whole floor at once !
when I finish a typical floor slab pouring ! when can I start next floor column work?
Thanks Again
Ahmad
Hi Ahmad
I am assuming that you have no experience whatsoever on insitu concrete.
You have been told that the insitu structure is usually achieved halfway through the project duration - or at least that is what I think you said.
If so that is not true - weathertight condition is usually about half way through the the project.
You do not say what is the structure for foundations and basement levels so I am are starting from the ground floor slabs or the pile caps. Let me know if you need any help on the foundation section.
First you need to look at the engineering floor plan to see where the expansion joints are located as this will determine the size of each section.
If there is more than one section then you have to decide the number of gangs to be deployed. It is good practice to bring every level up before starting on the next level.
A simple cascade of tasks using bottom up planning from level 4 is:
Form Column Kickers - 2 day
Rebar Columns - 3 day unles prefab then 1 day
Form columns - 3 day
Pour coulumns - 1 day
Strike Column forms - 1 day
Place Table slab forms - 1 to 2 day depending on crane capacity and how high up.
Edge slab forms - 2 day
Rebar slabs - 3 day unless prefab and sufficient crane capacity and the 1 day.
Pour Slabs - 1 day if pumped
5 calendar day curing period > Strike Table Forms > M&E Horizontals Ready to Start
28 calendar day Curing period > Strike Back Props > Interior blockwork ready to start.
There should be a FS Link between areas and / or levels for strike and place forms unless you are using multiple forms.
Repeat process for each area between expansion joints until the level is complete and then move to the next level.
I hope that helps
Best regards
Mike Testro
Email: PPadmin@planningplanet.com
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