Cold Weather Concrete Webinar Final - Wisconsin … · · 2015-10-27cold weather concrete travis buckley, e.i.t., wi datcp conservation engineer drew zelle, wi datcp engineering
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Cold Weather ConcreteTRAVIS BUCKLEY, E. I .T. , WI DATCP CONSERVATION ENGINEER
DREW ZELLE, WI DATCP ENGINEERING SPECIALIST
AMY R. MOORE, P.E. , NRCS CIVIL ENGINEER
TopicsWhat do we mean by cold weather concrete?
Why do we care?
What does Spec 4 require?◦ What changes in the concrete mix?◦ What changes in construction practices?◦ What additional inspection is required?
Cold Weather, DefinedWI Construction Specification 4‐ Concrete, Section 13 defines cold weather:
“When the minimum air temperature at the local job site is less than 35 degrees Fahrenheit (forecast temperature and verified with a maximum/minimum thermometer at the start of the morning shift)”
http://www.concretenetwork.com/cold‐weather‐concrete/
Why should I care?Water in the concrete mix can freeze if it gets too cold.
Frozen pore water cannot be used to hydrate cement.
Water expands as it freezes, causing internal damage to the concrete.
Frozen ConcreteNot as watertight
Susceptible to subsequent freeze thaw damage
Delayed cure time◦ 1/3 longer per 10 degrees
Before 500 psi‐ up to 50% loss of strength
http://cfawalls.org/concretefacts/2013/11/15/casting‐foundation‐concrete‐in‐cold‐weather/
PermeabilityMicro fissures caused by frozen water
http://www.torange.us/Backgrounds‐textures/texture/Frozen‐concrete‐Micro‐survey‐1702.html
Freeze Thaw DurabilityScaling/Spalling
Cracking
Crumblinghttp://engr.psu.edu/ae/thinshells/module%20iii/case_study_4.htm
http://www.diychatroom.com/f19/concrete‐spalling‐92286/
Heat of HydrationConcrete does produce heat as it cures
Capture the heat; keep the concrete curing
http://www.ecocem.ie/technical,wind_farms.htm
TopicsWisconsin Construction Specification 4 – Concrete (Version 3/2015)
Concrete Materials & TemperatureCuring PeriodOther Materials
Concrete MixingMixing water temperature shall < 100° F
Aggregate temperature shall be < 100° F
http://iti.northwestern.edu/cement/Figures/Fig1_3.JPG
Concrete Transport & PlacementDuring production or transport the concrete temperature shall be < 80° F
*At the time of placement the concrete temperature shall be > 55° F
http://www.daviddarling.info/encyclopedia/C/AE_concrete.html
Curing PeriodAir Temperature adjacent to the concrete surface:
> 32° F for the first 10 days
> 40° F for 7 of the first 10 days
*Curing Period = 7 cumulative days
Cool gradually: < 40 degrees in 24 hours
Type III CementHigh strength in a shorter period
Must conform to ASTM C 150
*Curing Period = 3 consecutive days
Portland Cement Association, Design and Control of Concrete Mixtures, Thirteenth Edition, Page 23.
Accelerating AdmixturesQuicker set time and high strength in a shorter period
Must conform to ASTM C 494, Type CNon‐Chloride!
Examples:◦ SikaSet NC by Sika◦ Polychem Super Set III by GRT◦ MasterSet FP 20 by BASF
*Curing Period = 3 consecutive days
Other MaterialsExpansive Waterstop
Repair Materials◦ Site Mixed Portland Cement Mortar◦ Bonding Grout◦ Epoxy Mortar and Epoxy Compounds
*Follow Manufacturer’s Recommendations!
Construction Inspection of Concrete During Cold WeatherMake sure you’re in a cold weather condition as identified in the standard. Construction costs will increase 20‐30% in this environment.
“the minimum air temperature at the local job site is less than 35 degrees Fahrenheit”
‐Use local forecasts and verified with an on site maximum/minimum thermometer as verified at the start of the morning job shift.
Be Prepared for the Cold Weather Concrete‐Plan for it up front to avoid surprises in change in the weather.Preconstruction Conference‐Items to consider:
‐Does the contractor have the materials to maintain temperature?
‐Does the contractor have the means to record and log temperatures?
‐Can the subbase remain unfrozen for adjacent pours?
‐Can the water stop be placed per the manufacturer’s requirements.
‐Does the inspector have an infrared thermometer? Max./Min. thermometer
‐Will there be a change in the concrete mix?
‐Has the mix design been approved by the designer?
‐Are the admixtures free from Calcium Chloride?
‐Is the landowner aware of the increase in cost?
Prior planning helps the placement of concrete go smoother and minimizes the risk of cold weather concreting.
Inspection Requirements‐Temperature‐Daily Temperature at local job site
‐Air adjacent to the concrete at several points along concrete surface for all concrete curing periods. (can’t be less than 32 degrees during the first 10 days) AND (shall be maintained above 40 degrees for a period of at least 7 accumulated dates which must occur during the first 10 days after the concrete is placed)
‐Temperature at time of placement (should be 55 degrees)
‐Verification that the subbase was not frozen at time of placement
‐Documentation can be a written log of temperatures, field notes, annotations in project logbooks, etc., just be sure and document it even if it doesn’t meet the requirements of WCS #4
Options to Maintain Temperature: (Remember it’s the contractor’s responsibility and area of expertise.)
Temperature Protection ExamplesRemember:
‐No set requirement for coverage other than temperatures have to be maintained. No single method may work, might need combinations. Edges and corners need extra precautions.
‐Sub‐base must be kept thawed too
‐Combustion heaters must be properly vented and can’t overheat or dry concrete surface.
‐Maintenance of covers, straw, combustion heaters etc. must be taken into account for curing period of concrete.
Inspection Requirements‐Mix Design‐Follow all requirements of WCS #4 (as previously discussed)
‐Plus documentation that the admixtures do not contain calcium chloride
‐Obtain this documentation prior to pour.
Inspection Requirements‐Summary‐Prepare for cold weather concrete‐pre‐construction conferences are critical
‐Verify mix design well prior to pour including admixtures
‐Ensure that manufacturer’s recommendations for water stops can be met given the temperatures.
‐Ensure that subbase is not frozen
‐Maintain and document temperatures
‐If in doubt‐recommend not to place the concrete
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