ParsCo cold weather construction tips for concrete and masonry work

• Insulating sheets,
• Straw-plastic,
• Heating coils,
• Insulating blankets, and
• Windbreaks.

• ASTM C 150 Type I cement 7 days
• ASTM C 150 Type II cement 10 days
• ASTM C 150 Type III cement 3 days
• ASTM C 150 Type IV or V cement 14 days
• ASTM C 595, C 845, C 1157 cements variable

• Maintain a proper water-cement ratio. The water to cement ratio should not be more than 0.40 under freezing conditions.
• If temperatures are too cold, a propane heater and polyethylene enclosure could be used to maintain temperatures hot enough, to avoid freezing point.
• Use Portland cement Type III, cement that helps in setting without reducing concrete’s quality. It is important because high moisture content can induce corrosion problems in steel reinforcement.
• Control chloride ions by suing fly ash, silica fume and furnace slag.
• Leave forms in place as long as possible.  Corners and edges are most vulnerable.
• Removing the blankets suddenly in cold weather can cause a temperature differential to build up between the outside of the concrete and its middle. This can cause cracking from the thermal differential, but typically only in thicker members.
• Concrete under water curing for flatwork applications becomes easy with previous concrete. Pervious Concrete is all coarse aggregates and it contains a negligible percentage of fine aggregates, especially sand. Additives are mixed into it that do not allow water to penetrate inside the concrete surface. Pervious concrete is suitable for constructing pavement as it does not soak in water but allows gallons of water pass through it without damaging concrete pavement and strength.
• Wait until all bleed water has evaporated. Curing concrete in cold weather will produce a slower curing procedure, so the concrete is setting slowly, and bleeding will also start later than expected. Be prepared to handle more bleed water than regular concrete placement.
• While concrete is being cures, verify the concrete temperature using an infrared temperature gun.
• To determine how much insulating value you need to keep the concrete at 50°F, check out the tables in Chapter 7 of ACI 306. The insulation needed is based on concrete thickness, cement content, and the lowest air temperature anticipated for the protection period.
• Seal concrete by applying concrete sealant so water does not seep inside the concrete. Concrete sealants will extend concrete’s life, and will reduce the concrete curing failure. In extremely cold regions, only a breathable concrete sealant must be used, as it will allow the evaporation of water and moisture, helping in fast setting of the concrete.

• It is recommended to use a speed hydration by using high-early cement or by using an accelerator. Caution: Type III cements could change mortar color varying the required appearance.
• Analyze how admixture could affect cold weather construction and reactions.
• Place materials on planks and cover them with tarps.
• All masonry materials should be completely covered to prevent wetting by rain or snow.
• Some masonry materials might need to be heated prior to use, so cement hydration can occur properly.
• Masonry units with high rates of absorption will accelerate stiffening.
• Calcium chloride (at a limit of 2% by weight of cement) is commonly used in concrete as an accelerator, but its use in mortar is prohibited by the Specification for Masonry Structures (ACI 530.1-95/ASCE 6-95/TMS 602-95).
• Place masonry on unfrozen surfaces because ice reduces bond and when it melts the masonry could move.

• Temperature above 32 degrees Fahrenheit- Cover walls with plastic to prevent water entering masonry.
• Temperature between 32 and 20 degrees- Cover walls with ½ inch insulation blanket to prevent or reduce rapid heat loss, or block water entering masonry.
• Temperature between 20 and 0 degrees- Cover wall with plastic insulation blanket, approximately one inch thick, or maintain a heated area to 40 degrees for two days following installation.

• Mortar shall be maintained above freezing until used.
• Sand or water shall be heated to produce mortar above 40 degrees Fahrenheit.
• Heat sources might be used on both sides of the masonry under construction.
• Wind breakers shall be installed if wind conditions are in excess of 15 miles per hour.
• Glass unit masonry shall not be laid during cold periods.
• Heated enclosures are recommended when the temperature drops below 20°F.
• Most commercially-available masonry ‘antifreeze’ admixtures are actually accelerators rather than freezing-point depressants. ASTM C1384 provides criteria for evaluating admixtures, including accelerators, for use in masonry mortars.
• It may be necessary to heat sand to thaw frozen lumps when temperatures fall below freezing.
• To avoid flash set, heated water should be combined with cold sand in the mixer before adding cement.
• Do not lay masonry units having either a temperature below 20°F or containing fro­zen moisture, visible ice, or snow on their surface.
• Masonry units should be kept dry, although very high absorption fired-clay brick may need to be wetted — but not saturated — prior to use.

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