HOT | COLD WEATHER CONCRETING
Weather conditions greatly affect concrete quality. The temperature of the air, humidity level, wind speed, and temperatures of the surface where concrete is to be placed, all play an important role in the quality of concrete and must be taken into consideration.
In general, due to high temperature, the evaporation of water from the mix takes place that results in loss of workability and higher plastic shrinkage. The early setting due to high temperature results in greater difficulty with handling, compacting, and finishing of concrete. On the other hand, the fresh concrete with low temperatures starts freezing due to which the mixing water converts to ice resulting in an increase in the overall volume of the concrete. As no water is then left for chemical reaction, the setting and hardening of concrete are delayed, and concrete produced will be of low strength. Hence proper protections are vital, when concrete is placed in abnormal weather conditions either hot or cold.
Listed below you will find tips and resources to help you place your cold or hot weather concrete. If proper precautions are taken, it is possible to successfully place your concrete during cold and hot weather.
Cemstone Companies are not responsible for concrete failures due to improper hot/cold weather plans, improper placing practices, incorrect mix design selection, inadequate protection, improper curing and/or inadequate maintenance. Please consult Cemstone’s Exterior Maintenance Guideline for recommendations on maintaining exterior concrete.
COLD WEATHER CONCRETE
The following information will help you successfully place concrete in cold weather. As always, Cemstone is committed to our mutual success and following these guidelines will result in satisfied customers.
Special precautions are needed for placing concrete in cold weather conditions. Cemstone uses heated mixing water and if needed, heated aggregates to keep concrete temperatures at the time of batching above 60°F in cold weather.
The slider below explores ten items that will help prevent cold weather concrete issues.
Hot weather is any combination of the following conditions that tends to impair the quality of freshly mixed concrete by accelerating the rate of moisture loss and rate of cement hydration, or otherwise causing detrimental results:
- High ambient temperature
- High concrete temperature
- Low relative humidity
- High wind speed
- Solar radiation
HOT WEATHER CAN OCCUR DURING THE SPRING, FALL AND WINTER MONTHS.
The following list of practices and measures to reduce or avoid the potential problems of hot weather concreting are:
- Schedule a pre-placement meeting to discuss the requirements of hot weather concreting
- Select concrete materials and proportions with satisfactory records in hot weather conditions
- Reducing and controlling the temperature of the fresh concrete
- Use a concrete consistency (slump) that permits rapid placement and effective consolidation
- Minimize the time to transport, place, consolidate, and finish the concrete
- Plan the job to avoid adverse exposure of the concrete to the environment; schedule placing operations during times of the day or night when weather conditions are favorable;
- Protect the concrete from moisture loss during placing and curing periods
Potential problems for concrete in the freshly mixed state are:
- Increased water demand
- Increased rate of slump loss and corresponding tendency to add water at the job site
- Increased rate of setting, resulting in a greater difficulty with handling, compacting and finishing and a greater risk of cold joints
- Increased tendency for plastic shrinkage and thermal cracking
- Increased difficulty in controlling entrained air content
Potential deficiencies to concrete in the hardened state may include:
- Decreased strengths resulting from higher water demand
- Increased tendency for drying shrinkage and differential thermal cracking from either cooling of the overall structure or from temperature differentials within the cross section of the member
- Decreased durability resulting from cracking
- Greater variability of surface appearance, such as cold joints or color difference due to
different rates of hydration or different water-cementitious material ratios (w/cm)
- NRMCA CIP 12 Hot Weather Concreting
- Cement Burn Warning
- PCA – Hot Weather Concreting – Part 1
- PCA – Hot Weather Concreting – Part 2
- OSHA Occupational Heat Exposure
- Complete Hot Weather Concrete Packet
- Cemstone Aggregate Quality ASR Letter
- Technical Data Sheet Cemstone Cure & Seal Plus
- American Concrete Institute
ACI-305 Hot Weather Concreting
- NRMCA CIP12 – Hot Weather Concreting
Available to purchase at www.nrmca.org