Climatic conditions such as ambient temperature, wind speed and relative humidity can significantly affect water loss at the concrete surface. In addition to making finishing more difficult, a surface that dries too rapidly increases shrinkage and the risk of cracking. The chemical hydration reaction of the cement requires a sufficient amount of water as well as appropriate temperature conditions to allow the concrete to achieve the specified strength and durability.

Ontario Redimix has developed a Concrete Evaporation Calculator to estimate the evaporation rate of concrete under current climatic conditions and recommends mitigation or protection measures to be put in place to ensure the quality of your concrete pour. Generally, when the evaporation rate exceeds 0.5kg / m² / hour, mitigation measures should be considered.

As a partner committed to your success, in addition to providing concrete to carry out your work and deliver on your projects, Ontario Redimix offers you products and value-added solutions that can help you contend with any challenge, including restrictive climatic conditions. Contact us if you need additional advice for your concrete work.

Disclaimer:

This Concrete Evaporation Calculator should be used only as a guide and the user should contact us for advice on mitigation measures to ensure the best quality results. Ontario Redimix is not responsible for incorrect information provided by the user or incorrect use of the Concrete Evaporation Calculator.


air temperature ºC
RELATIVE HUMIDITY (%)
WIND VELOCITY (KM/H)
CONCRETE TEMPERATURE
EVAPORATION RATE (KG/M2/H)

The evaporation rate is greater than 0.50 kg/m²/hr. We recommend the following mitigation measures to help achieve a good quality concrete pour.

What can be done on site:

  • Plan deliveries to minimize wait time at the job site. Prolonged mixing of the concrete increases the concrete temperature;
  • Moisten the surfaces to which the concrete will be in contact (formwork, reinforcement, sub-grade, etc.);
  • Protect concrete surfaces exposed to the sun and wind from drying out by applying a fine mist, water fog spray using a pressure washer;
  • Cover the concrete surface with polyethylene film between the finishing steps;
  • Provide windbreaks when high winds are blowing and the relative humidity is low;
  • Provide sufficient staff to allow rapid implementation;
  • Undertake concrete cure immediately after final texturing;
  • Place and finish concrete at night or early in the morning;
  • Consider ordering ice to lower concrete temperatures at placement;
  • Delay the concrete placement until ambient conditions improve on site;
  • Apply a liquid evaporation-reducing surface film on the concrete surface (i.e. evaporation retardant) immediately after screeding or before finishing operations;
  • Use site-added superplasticizer or order plant-added superplasticizer instead of adding water on site.

What can be done at the concrete plant:

  • To cool the concrete mix the plant can add cool water or incorporate crushed ice. In cases where concrete design requires minimal water (high performance concrete), it may become necessary to use liquid nitrogen instead;
  • Use a retarding agent;
  • Use evaporation retarding agent additives before starting, finishing or curing with water;
  • Adding micro-fibres can help reduce plastic shrinkage.

For more information on our solutions, please contact us.

The temperature is below 10oC. We recommend the following mitigation measures to help achieve a good quality concrete pour.

What can be done on-site:

  • Avoid placing concrete in extreme conditions (below -15 ° C);
  • Establish procedures to remove any snow or ice in the formwork prior to concreting operations;
  • Provide the necessary supplemental heat required to ensure that forms, sub-grade, and reinforcing steel are maintained at a minimum temperature of 5 °C well prior to concrete placement;
  • Conduct a pre-pour meeting to define protection methods during pour, including typical equipment like blankets, insulation, as well as heating and cure methods;
  • Increase the degree of protection when the temperature drops;
  • Use heated shelters and insulating blankets;
  • Wet curing methods are typically not recommended during cold weather conditions since the concrete will not have sufficient time period to air dry before first exposure to freeze/thaw cycles;
  • Plan to verify the concrete temperature once the concrete is in place;
  • Provide procedures to prevent excessive drying of concrete caused by excessive heating and wind;
  • Cool the concrete slowly before exposing it directly to cold air;
  • Establish methods to verify the quality of concrete in place.

What can be done at the concrete plant:

  • Winter mixes such as our Thermalcrete mix designs can be ordered to help offset the cold weather effects;
  • Concrete should be ordered using the lowest practical water slump since this will reduce bleeding and setting time;
  • Chemical admixtures such as accelerators can be used to reduce set time and accelerate early strength gain of concrete while superplasticizers can be used to improve the workability of the concrete for ease of placement.

For more information on our solutions, please contact us