Key Questions to Ask When Ordering post tension system solutions

Concrete
Post-tension Slab Checklist

Copyright 2007 Marshall Hansen

• Rev. 20081026 (powder puff link)
• 20080422 This is the most popular page in my blog, and I sincerely appreciate all who stop to look. This list is compiled from field notes and observations. I’m adding more comments as I see issues in search inquiries. Also, I will be trying to (re)organize the list sequentially though many issues occur concurrently, and many issues apply to any slab pour. The simplest advice I can give to anyone is to follow the plans. If you do this, the risk belongs to the engineer and architect for the design. Any change from plans must be in writing – RFI or letter from PT engineer
• This applies primarily to light-duty PT, multi-family/residential from GC point of view
• Please add any suggestions or comments in the comment box, and I may add them to the list
• See another construction management checklist: Powder Puff Cleaning Checklist
• Link to this page as I will be updating continually – when you need it, you will have my latest edition. https://marshansen.wordpress.com/post-tension-slab-checklist/

Scope/contract issues

• Manpower required to maintain schedule, non-performance will be supplemented
• Daily reports to site Superintendent from sub foreman – # in crew, work done, comments
• Daily and ongoing clean-up, non-performance will be supplemented
• 24-hour notices to be given on time per condition, failure to act a second or subsequent time does not require notice to supplement
• No tolerance harassment policy – wolf whistles, gestures, ogling, yelling, etc.
• Sub is experienced in proper methods of PT components installation and storage of tendons
• Sub will install all materials per manufacturers’ specs or assume responsibility (waterstops, etc.)
• Method of elongation spelled out – how tendon is marked, who observes, who gets copies of lab report, etc.
• Batch mix and slump, flyash max, additives, if any
• Test cylinder break schedule – 3, 14, 28, extra; 7, 14, 28, extra; etc.
• Notes on PT engineer’s plans are requirements for install (while they may not be specified in scope)
• English-speaking supervisor/foreman on site at all times
• Sub will be included in pro-rata LDs if schedule is not maintained
• Immediately after pour, sub will clean area around the pump truck and spoils from trucks going to clean-out area if on finished pavement
• When form and finish crews are different sub-subs main concrete sub will have management on site throughout the process start to finish/clean up
• Inspection, permissions of off-site access for placement of pump truck if site layout will not accommodate pump truck for pour
• When asking for bids, if one subcontractor’s price is substantially lower than the other bids consider the possibility that the take-off is wrong, they have not read the specs/plans or made an error in calculations – probably all three. Be prepared for a request to re-engineer the slab using less concrete. The lowest bid does not always save you money

Pre-pour

• Are there any discrepancies between Architectural and Post-Tension Engineer plans? Check all dimensions and features. If so, RFIs must be obtained to proceed. Meanwhile,
• Check site layout for building orientation – is it mirrored or flipped from Architectural drawings?
• Are pilings required? They should be done by now, and that’s another checklist, my friend.
• Inspection checklist showing required inspections from engineer, architect, client, city, county, parish, municipality, ACOE, state or appropriate enforcement division(s), who calls them in? Copies to GC at the site.
• Were lifts built up per soil engineer’s specs? Was sub-grade properly compacted? Did lab perform Proctor field test?
• Call the surveyor to stake envelope and finished floor, or other reference elevation/points as needed/desired (elevator pit) verify
• Envelope placement – four corners and reference other site benchmarks – verify
• Safety – rebar caps w/metal insert (no poke through), barricades around open excavations and forms, safety rails where necessary, trenches for access to elevator pit, OSHA conforming access. Continuous check
• Electricity available for form carpenters (temporary power) or do they have a generator?
• Is slab elevation per plans – verify with surveyors stake
• MEP – other trades rough complete and inspected
• Verify all sleeves and proper placement for any utilities under slab, check PT engineer’s plans/spec for placement requirements
• Elevator pit layout – verify
• Elevator pit may require sleeves for sump pump pipes, etc. Verify size and placement
• Elevator base may have a sump pit – verify location and dimensions. Confirm with plumber’s submittal for sump pump dimensions
• Is the waterproof membrane/Bentonite required under the elevator pit base? Coordinate with the concrete sub
• Does the elevator base have a water stop flange or membrane? Does sub have on site? Does sub have the proper iron to make a watertight joint on site? Keyways? Do you have mfg installation requirements? verify
• Trenches proper depth/width
• Beams and footing proper dimension and shape
• Are there special footings/thickened beams for stairs, chimneys, steel columns, structural features – where, shape, how deep and wide, rebar, etc.
• Slab forms proper elevation relative to pad for slab thickness
• Termite treatment and inspection
• Vapor retarder properly installed, coverage and material per spec (6, 8, 10 mil etc)
• Forms checked per Architectural drawings, check details pages
• Forms properly braced to withstand hydrostatic pressure
• Are two-sided forms properly braced and tied off – inside and outside?
• Are steel form systems properly assembled, anchored, braced, w/ strongbacks, etc?
• Is slab insulation required and on site? Installed properly?
• Block-outs, recessed areas for tile floors, marble thresholds, ADA showers properly formed
• Release (plastic, oil, silicone, diesel, etc) on brick ledge forms on flat areas so they can be removed without damaging, chipping , finished slab. Convenient but not required. Spec may have a note on release agents accepted
• Brick ledges continuous around columns and returns verify per plans
• Slope floor in rooms with floor drains – formed or marked with stake for hand finishing
• No slope of approach to exceed ADA (per plans or half of entries)
• Control joint and forms properly set, dowels level/on proper plane and stationary – strip form on the proper side
• Tub box placement, ballast, depth, properly installed – cavity for p-trap chase on proper side
• Proper size of rebar per plans/spec
• Post-tension cable anchors installed facing the proper direction – dead and live ends
• Post-tension cables and rebar properly spaced, chaired and tied per plans and mfg specs
• Corners, beams, walls and footings properly reinforced with rebar – hairpins per plans, if required
• Proper tie-in of chairs to post-tension cables at intersections and chairs under rebar in beams and footings – this is repeated because it is neglected – look again. If they are not tied to tendons they will get knocked off by finishers during pour
• Plumber check for obvious damage to risers, etc., from form crew, termite applicator. Check 10-foot head or air re-test per specs
• Verify batch mix with spec, sub and plant – fly ash, slump, curing compound
• Plan placement of concrete pump at least one day ahead and ensure access through the site to pour. Are any power lines adjacent to pour? Do you have trenches from electric primaries, civil – storm sewer, sanitary sewer, water, etc. and were they compacted properly? Flag off any unstable areas, coordinate with concrete sub
• Order light tower(s) to be delivered the afternoon before an early morning pour. Verify
• Verify sub has sufficient crew to properly finish slab in workable time
• Verify finisher crew arrival time – coordinate with the pump truck and plant
• What is the weather forecast? Hot, cold, wet, low humidity??
• Are power trowels on site?
• Is curing compound on site, staged near slab? Does sub have operable applicator/sprayer?
• Have these phone numbers already entered in your cell phone and PDA:
  • 911 or local emergency direct number if using an out-of-state cell phone (call county they will give you the direct number)
  • Concrete sub PM, lab, pump, plumber, concrete sales rep, back-up GC staff, emergencies and extra labor needed
  • Printed directions to hospital

• Plan truck cleanout area if not on site plans. Low cleanout dumpster with liner can be ordered from pump/dumpster/waste company. Plan delivery one day ahead and clearly mark off limits for construction trash until after pours are completed. Do not create mud pit
• EPA entrance or wash area for truck tires ready to minimize mud, silt carried off-site
• Pipe risers, drains, in-floor receptacles, cleanouts capped, plugged, or taped to prevent dirt and concrete contamination, tops and covers set at right height relative to finished floor surface – level with finished surface VCT, carpet, slab, etc verify with plumber and electrician
• Low temperature pours require blankets. Be sure there are enough on site to cover the pour and you have materials (weights) to hold the blankets on the slab.
• Are there any city noise ordinances restricting construction noise to specific times? Will this affect early morning pours?

Pour

• Plumber(s) on duty ready to work – mud boots, pvc saw, cleaner and glue, markers, tub boxes, sand, pvc fittings and pipe, spare cleanouts, laser level, etc.
• Anchors for sill plates per spec (bolts, depth, type, spacing )
• Anchors properly spaced in shear walls
• Steel footings or j-bolts for steel column/post placement – with template
• Call lab for pour inspection (lead time varies per lab), slump and test cylinders, what is required in spec?
• Record truck number, time of delivery, slump – if too wet/dry, if water added
• Verify designed batch mix and strength with plant and truck documents, during pour track travel time from plant to site
• All door thresholds are rechecked for level
• No added water unless specifically allowed in batch design with required number of revolutions of mixer reached, verify
• If primary concrete sub hires sub finisher they must have crew/agreement to clean all spoils, butter around cleanout area and pump truck during/after each pour (it may be in the scope but make sure they are there to do it)

Post pour/finishing

• No slope or broom on thresholds
• Broom entries perpendicular to the slope, not parallel with slope
• Curing compounds, sealers, hardeners, pump sprayer, misters, etc. ready for application per specs, manufacturer’s instructions and plans
• Observe power trowel operators – are they hitting pipes?
• When do you perform the first pull and when do you perform the final pull is based upon plans, engineer plan notes (usually on PT pages) and/or specs. The first pull is usually within x days of pour. The lab will break cylinders based upon the schedule you give them, and the final pull will occur once a PSI threshold is reached. This number is also in plans/specs. If not call your PM. If PM doesn’t know, call PT slab engineer.
• Coordinate, verify elongation process/method, and recording with sub and lab before the first pull. How is length marked, measured, cylinder break x days after pour, etc.
• Project manager to verify work by concrete sub is complete via on-site Superintendent before releasing payment – spoils clean up, forms removed, block-out mistakes repaired, damage from trucks to landscaping/existing paving, etc.
• All subcontractors should be reminded from time to time at weekly on-site meetings no chicken hammers, jack hammers, quickie saws, hammer drills are to be used on the slab without notifying the GC and getting approval before starting work. Depth of work must be confirmed, and tendons must be located properly.

After you discover the plumber, electrician, another sub or architect/engineer omitted a sleeve, conduit, anchor, piling, footing, whatever and now has to break the slab to replace, install, remove, repair, etc. – what shall I do?

• DO NOT attempt to locate tendons by sight using live end and fasteners from dead end for reference. During the pour, the finishers can move tendons 6 or more inches up, down, side to side, etc. from placement pre-pour.
• Call the testing lab and ask them for a tendon locate.
• The price for the technician and the locating instrument will be less than the cost of replacing a broken tendon and a whole lot less than impaling the elevator sub working in the elevator pit when the plumber cuts a tendon moving a floor drain 60 feet away. (No, this did not happen to me but it is possible and you get the point. Work safe. M)

Tendon Repair

Did you attempt to repair plumbing, electrical, sleeves without calling the lab for a locate, finding a broken tendon after a sub installed a tub, anchor plate, etc? The slab is over-engineered and depending on the location of the broken tendon, a repair may not be required. This is a decision only the PT engineer can make. Prepare an RFI with the location clearly described and marked on a tendon layout diagram from the plans, ask if a repair is necessary, then send the RFI and follow RFI response instructions.

If repair is required, coordinate with the repair tech and determine what prep work is needed to complete the job.

Check revision date for updates. Work safe.
Marshall

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