March 2, 2020 - Daily Update
Winter is here so please remember to observe cold weather concrete precautions when applicable. ACI 306R defines cold weather as any time air temperatures are expected to fall below 40F during the protection period. In addition, all surfaces, rebar, formwork, subgrade etc. should be above 32F to prevent freezing at the interface. After concrete (up to 12” thick) is placed, temperatures of at least 55F must be maintained for 72 hours. The use of insulating blankets, heated mats or plastic and straw must be on site at time of inspection during cold weather.
Masonry Cold Weather Precautions: Cold Weather Construction Requirements Ambient temperature Cold weather procedures for work in progress Above 40°F (4.4°C) No special requirements.
Below 40°F 32°F to 40°F Heat sand or mixing water to produce mortar temperature between 40°F and 120°F at the time of mixing. Heat materials for grout only if they are below 32°F.
25°F to 32°F Heat sand or mixing water to produce mortar temperature between 40°F and 120°F and at the time of mixing. Keep mortar above freezing until used in masonry. Heat materials to produce grout temperature between 70°F and 120°F (21.1°C and 48.9°C) at the time of mixing. Keep grout temperature above 70°F (21.1°C) at the time of placement. 20°F to 25°F In addition to requirements for 25°F to 32°F (-3.9°C to 0°C), heat masonry surfaces under (-6.7°C to -3.9°C) construction to 40°F (4.4°C) and use wind breaks or enclosures when the wind velocity exceeds 15 mph (24 km/h). Heat masonry to a minimum of 40°F (4.4°C) prior to grouting. 20°F (-6.7°C) In addition to all of the above requirements, provide an enclosure and auxiliary heat to keep air and below temperature above 32°F (0°C) within the enclosure.
Ambient temperature Cold weather procedures for newly completed masonry (minimum for grouted; mean daily for ungrouted) Above 40°F No special requirements. Maintain autoclaved aerated concrete (AAC) above 32°F for the first 24 hours after thin-bed mortar application. 25°F to 40°F Cover newly constructed masonry with a weather-resistive membrane for 24 hours after being completed.
20°F to 25°F Cover newly constructed masonry with weather-resistive insulating blankets (or equal protection for 24 hours after being completed. Extend the time period to 48 hours for grouted masonry, unless the only cement used in the grout is ASTM C 150 Type III. 20°F Keep newly constructed masonry above 32°F for at least 24 hours after being completed. and below Use heated enclosures, electric heating blankets, infrared lamps, or other acceptable methods. Extend the time period to 48 hours for grouted masonry, unless the only cement used in the grout is ASTM C 150 Type III.