Latex Mondified Concrete Mix Design
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- Submitted by lafarge annually or on a project specific basis if other supplier used, refer to specifics.
- Submit to central lab for design approval
- 3-copies submitted of manufacturer test reports
- sample of admixture needs to be submitted to central lab, 20 days prior to use on project for acceptance testing.
- One sample is usually adequate for most projects.
- Cement - type I or type II, (from same supplier) only one type
- Water - mixing, cleaning or wetting decks
Aggregates - CA
- Stockpiles - check for miosture the day of pour, protect from moisture cover with plastic etc.
- If excessive moisture is present in fine aggregate it will reduce available mix water and may not be usable for placement.
Definition of excessive moisture: if aggregate moisture higher than available mix water
Proportioning And Mixing Equipment
- Submitted by supplier
- State personnel should verify calibration of trucks
- (be present if possible)
Calibration Of Trucks
- Calibration of cement
- Calibration of aggregates
- Calibration of latex meter
- Must meet requirements of specifications
- Sound and mark deck for delamination
- Jackhammers of 30kg/60 lbs for initial removal operations
- Smaller chippers of 15kg/30lbs or smaller if the projectmanager feels that larger hammers are detrimental to bridge deck.
- Operation of jackhammers no more than 60% from horizontal.
- If less than 50% of deck thickness remains the deck should be taken full depth except in isolated random locations as determined by project manager.
- Calibration of equipment is necessary
- Equipment must be operated by qualified personnel
- Replace as necessary, lapped a minimum of 0.30mm/12" or as directed by project manager.
- New bars and existing bars must have a minimum of 20mm or 3/4" clearance around exposed bars.
- Sandblast deck and rebar to gray metal (refer to new specs for additional requirements).
Forms for Full Depth Repair
- Form for areas less than 0.5 sq/m (4 sq/ft) can be suspended from rebar.
- Larger areas must be supported from primary members of superstructure or shored from below.
- Contractor, state and supplier should all be present and should be scheduled at least two days or more prior to placement
- Cover specifications, methods of placement, inspection and potential problems
Dry Run Of Bridge Deck
- Covered in detail in pre-placement section of training session.
Setting of Gradeline
- Surveyor should shoot existing gradeline, plot profile and project new gradeline.
- This must be submitted to project manager prior to approval.
- Adjustments should be made to grade to produce a smooth riding surface and shall result in at least the minimum concrete fill as shown in plans/contract.
- Bulk heads and deck joints should be installed to proper grade and longitudinal joints should avoid wheel paths as much as practical.
Placement (Finishing Machine Must Meet Specification Requirements)
- Pre-wet deck: wet deck for 2 hours before pour - inspector should verify.
- Cover with plastic to keep moisture in and protect deck from spills.
- Check rate of evaporation at or near deck surface, no more than .73 kg/m2/h (.15 lbs/ft2)
- Ambient temperature of not less than 7 c (45 f)
- Starting out, pour a little latex modified concrete, then broom it over the deck and edges, spreading the mortar mixture.
- Aggregates need to be removed. Keep the mixture ahead of the pour, but not so far it dries out (2m or 6' +/-)
- Note: complete application/coverage of mortar is critical to bonding of overlay to existing surface.
- Don't place more than 3 meters ahead of finishing machine, need to place continuously.
- A delay of 5 to 20 minutes cover ends of concrete with burlap.
- If stopped more than 20 minutes set a bulkhead in deck.
- Make sure fluids don't settle in low/removed areas - have air compressor available to blow out fluid
- Minimal hand finishing - wood floats & fresno only
- Vibrator should be used at all partial depth areas and against edges, bulkheads and expansion joints
- Air, temperature, unit weight; run as usual
- Slump - wait 5 minutes set concrete aside and do not disturb
- If not in specs, adjust mix and retest
- Clean equipment immediately! Wear old clothing/shoes
- Do occasional checks of water/cement ratio and latex yield at least 3-4 per truck.
- Place double layer of clean burlap (approved equal)
- Timing is everything! (better too soon than too late) 15 -20 min.
- Lightly fog spray it, then place white plastic
- Keep burlap wet for 48 hours. verify burlap is wet entire 48 hours
- Cold weather curing (0 C/32 F)
- Continue wet cure until cylinders break as per specs
- Straight edge deck. Follow criteria as in previous section (same tolerances)
- After curing, check for delamination/bonding
- If not acceptable, remove and replace (contractor expense)
- Groove it, apply hmwm to cracks if any