Climate Overview:
The mid-south climate features humid, hot, long summers and cool winters, with only brief periods of cold weather. Spring and fall are short. Cool winters with temperatures ranging from 40 F and 50 F can sometimes give way to a winter cold front that drops temperatures into the lower 20s. However, these occurrences are usually short lived. Summer temperatures rise to the upper 90s and can exceed 100 F for long periods. Rainfall ranges from 24 inches in the western areas of central Texas to 40 to 50 inches in areas of Arkansas and Tennessee. Spring storms can be severe, with the threat of tornadoes in all areas.

Winter

Climate (December – March): Winters are cool. Day time temperatures range from 40 F to 50 F. Prolonged periods of very cold weather are rare. When winter storms do occur, ice and freezing rain is more common than snow. Cool temperatures allow year-round exterior concrete placement.

Mix Designs: Since all areas of this region see freeze-thaw conditions, air entrainment is common on all exterior concrete. Mix designs will have compressive strengths ranging from 3000 to 4000 psi, depending on the final use. The primary considerations include chemical set accelerators to help the concrete set faster and air-entrainment admixtures to help with freeze-thaw conditions. 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. Due to high 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.

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. Temperatures can vary greatly between day time and night time. Curing concrete in these regions usually requires the use of solvent-based curing compounds or cure-and-seal chemicals to avoid freezing.

Special Equipment:

  • Sprayers to apply curing compounds
  • 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 is very short in the Mid-South region. Cool winters change over to hot summers very quickly.

Mix Designs: Standard mix designs are the norm. Eliminating accelerators and adding fly ash into mixes is normal as the temperatures start to increase.

Placement and Curing Practices: Traditional placement and curing practices are the norm, as temperatures will dictate cold- or warm-weather practices.

Special Equipment: Sprayers to apply curing compounds; blankets for the rare late- season cold snap.

Summer

Climate (May – October): Hot and humid! Most areas experience hot to extremely hot conditions. Along with the hot weather come winds, especially in the more open spaces of the western states. In most areas, summer can be the most demanding time of year to pour exterior concrete.

Mix Designs: When hot conditions exist, hydration stabilizers, fly ash, and water reducers are common admixtures used to extend working life without affecting performance. The use of ice in mix water is also common to cool the concrete during transport.

Placement and Curing Practices: Hot-weather concreting practices are the norm in the summer months. With the combination of heat and wind, placement and curing of concrete in the summer can require extreme measures. In the hottest western regions, most all concrete placement takes place before 10 a.m. On many larger projects, concrete is placed at night or during the early morning hours to avoid the extreme sun and heat of the day. Rapid surface hydration is always a threat, so surface evaporative control agents and curing compounds are common on exterior concrete placements.

Special Equipment: Sprayers to apply curing compounds and surface evaporative control agents.

Fall

Climate (October - November): Because fall temperatures can still be quite warm in this region, hot-weather concreting practices are still necessary until late into the season. Coastal regions will see temperatures moderate earlier, while the deserts remain very warm. Early winter storms may begin in the late fall.

Mix Designs: Standard mix designs are the norm. Eliminating fly ash and retarders in mixes is normal as the temperatures start to decrease.

Placement and Curing Practices: Hot-weather concreting practices are in effect well into the fall in most areas of the region.

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

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