The Concrete Network

Climate Overview:
Although they cover a large geographic area, the states that fall within this region have similar weather patterns. To varying degrees, all areas have cold winters with snow, short springs, cool falls, and hot, humid summers. The farther north you go, the more severe the winters. Wisconsin, Minnesota and the Dakotas usually have snow on the ground for the entire winter. Precipitation ranges from 20 inches annually in the western states to 40 inches in the eastern and southern areas. Gulf of Mexico moisture is a constant, leading to hot, humid summers and snowy overcast winters. The spring and fall provide the most comfortable conditions, but are short in duration. Cold rain can continue into May, with cold temperatures beginning in early October. Exterior concrete work takes place year-round in the southern areas, but is uncommon in the northern areas of this region.

Winter

Climate (December - March): Winters are typically cold, damp and overcast. Most precipitation that falls is snow. Ground frost can vary from several inches to none at all depending on where in the region you reside. Exterior concrete is poured year-round with precautions.

Mix Designs: Cold-weather concrete mix designs are mandatory for all exterior concrete placed in this region during the winter. The primary considerations include chemical set accelerators to help the concrete set faster and air-entrainment admixtures to help with freeze-thaw conditions. Air entrainment should be mandatory in all exterior concrete placed in this region. Straight concrete mixes can also be used, as they tend to set faster than hybrid mixes. Using hot water to increase concrete temperature is a common winter practice.

Placement and Curing Practices: Cold-weather concreting practices are mandatory for all exterior concrete placed in this region during the winter. Due to extensive freeze-thaw conditions, this region is prone to spalling and scaling concrete. Proper mix design, placement, and curing are crucial for long-term concrete durability. The primary considerations include blankets for heat retention as well as the possibility of tenting in very cold conditions. Curing concrete in these regions usually requires the use of solvent-based curing compounds or cure-and-seal chemicals to avoid freezing. With cold temperatures, time is a factor, so pumping concrete becomes more common.

Special Equipment:

  • Sprayers to apply curing compounds
  • Ground heaters if the ground is frozen prior to the pour
  • Concrete pumps to speed the placement of concrete in cold conditions
  • Curing blankets and non-water-based curing compounds
  • Tenting
  • Proper cold-weather attire for crews pouring and finishing the concrete
Spring

Climate (April – May): Spring temperatures are cool and conditions can be wet. The threat of snow and freezing temperatures is usually gone by mid-April, but rain is always a consideration. Prolonged periods of rain can delay spring exterior concrete projects.

Mix Designs: Standard mix designs are the norm. In northern areas or regions with prolonged cold weather, chemical set accelerators may be used in concrete in the spring to help the concrete set quickly and uniformly. Due to extensive freeze-thaw conditions, this region is prone to spalling and scaling concrete. Air-entrainment admixtures should be mandatory in all exterior concrete placed in this region.

Placement and Curing Practices: Windy conditions can be common in the spring in western portions of this region. Plastic sheeting, surface evaporative control agents, and curing compounds should be available on all exterior pours in the spring. Proper water content and finishing are critical for long-term durability.

Special Equipment: Plastic sheeting to protect concrete from sudden rain showers; sprayers to apply curing compounds and surface evaporative control chemicals.

Summer

Climate (June – August): Hot, humid summers are the norm for this entire region. Extreme temperatures are rare. Periodic rain is common, and can occur at any time of the day. Most exterior concrete work takes place during the summer in this region.

Mix Designs: Dealing with high humidity and warm weather can require the use of admixtures to extend the set time. Hydration stabilizers and water reducers are commonly used to extend the working life of the concrete without affecting performance. Air-entrainment admixtures should be mandatory in all exterior concrete placed in this region.

Placement and Curing Practices: With high humidity and hot temperatures, quick placement is the norm for exterior concrete projects. Surface evaporative control agents should be available on all jobs, whether they are used or not. The use of curing compounds and cure-and-seal chemicals is commonplace for most exterior summer pours. Due to exposure of the hardened concrete to freeze-thaw conditions in winter, it is prone to spalling and scaling. Proper water content and finishing are critical for long-term durability.

Special Equipment: Plastic sheeting to protect concrete from sudden rain showers; sprayers to apply curing compounds and surface evaporative control chemicals; concrete pumps for rapid placement in hot conditions.

Fall

Climate (September – November): Fall provides the lowest humidity and most stable temperatures for pouring exterior concrete. Frost and freezing temperatures typically do not become a factor until November. Scheduling new exterior concrete work can be difficult, since concrete suppliers and installers are typically busy finishing as much work as possible before winter arrives.

Mix Designs: Hydration stabilizers and water reducers are commonly used to extend the working life of the concrete without affecting performance. Due to extensive freeze-thaw conditions, this region is prone to spalling and scaling concrete. Air-entrainment admixtures should be mandatory in all exterior concrete placed in this region.

Placement and Curing Practices: Surface evaporative control agents should be available on all jobs, whether they are used or not. The use of curing compounds and cure-and-seal chemicals is commonplace for most exterior pours. Proper water content and concrete finishing practices are critical for long-term durability.

Special Equipment: Sprayers to apply surface evaporative control agents and curing compounds; curing blankets; plastic sheeting.

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