Key Questions to Ask When Ordering post tension system supplier

Hiring a quality Unbonded Post-Tension Supplier can be the difference between a smooth construction project and a problematic situation. The Post-Tension (PT) supplier will play a key role in your reinforced concrete project. Therefore, general contractors and concrete contractors need to choose wisely.

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Traditionally, the Post-Tension Supplier is awarded their contract after other subcontractors in larger trades have been selected. Finding the right PT supplier to work with is essential to completing your concrete construction project on time and within budget.

Concrete
Post-tension Slab Checklist

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• 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 site
• Were lifts built up per soil engineer’s specs? Was sub-grade properly compacted? Did lab perform Proctor field test?
• Call 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 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 sump pit – verify location and dimensions. Confirm with plumber’s submittal for sump pump dimensions
• Is waterproof membrane/Bentonite required under elevator pit base? Coordinate with concrete sub
• Does elevator base have water stop flange or membrane? Does sub have on site? Does sub have proper iron to make 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 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 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 site to pour. Are any powerlines 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 pump truck and plant
• What is 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 out-of-state cell phone (call county they will give you 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, clean outs 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 clean outs, 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 recheck 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 clean out 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 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 pull first pull and when do you pull final pull is based upon plans, engineer plan notes (usually on PT pages) and/or specs. 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 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, other sub or architect/engineer omitted a sleeve, conduit, anchor, piling, footing, whatever and now have 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, find 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 repair is necessary then send RFI and follow RFI response instructions.

If repair is required coordinate with 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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