Best Practices for Concrete in Adverse Weather Conditions

Concrete in Adverse Situations

Concreting in Cold Weather

Precautions

• Fresh concrete temperature must be above 5°C.
• Ensure no contact between concrete and elements with temperatures below 0°C.
• Maintain concrete temperature above 5°C for one to three days.

Measures

• Modify dosage.
• Use high early-strength cement and hardening accelerators.
• Increase cement dosage beyond standard levels.
• Heat treated components.
• Heat water to 40°C and prolong mixing time.
• Heat water above 40°C and pour before adding cement and aggregates.
• Heat the aggregate or sand.
• Heat-treat the concrete placed on-site.
• Protect concreted surfaces.
• Delay formwork removal when the material acts as insulation.
• Create an artificial environment.

Note: In cold periods, setting and hardening are delayed. Account for the timing of stripping and removal of props. If in doubt, perform tests to determine resistance and adopt appropriate measures where necessary.

Concreting in Hot Weather

Prevent the evaporation of mixing water caused by high temperatures, low humidity, and high wind speeds. Rapid evaporation leads to a loss of resistance and increased shrinkage, resulting in cracks.

Measurements

• Use cold water, including ice chips or chunks.
• Protect aggregates from direct sunlight.
• Protect the concrete from sunlight to retain moisture.
• Add moisture to the concrete after placement.
• Avoid concreting at temperatures above 40°C, or 35°C for highly exposed surface elements.
• In high temperatures, water the forms and exposed surfaces for at least 10 days.

Underwater Concreting

This is a special case of concreting that requires specific techniques to avoid washing out the mix.

• Do not pour concrete into moving water (max velocity 2 m/s).
• Never pour in temperatures below 4°C.
• Use special cements with aggressive water to guarantee durability.

Recommendations

• Discharge Pipeline: Maintain the pipe filled with concrete so hydrostatic pressure exceeds the maximum expected in the formwork.
• Keep the tubing embedded in the concrete mass at a safe depth (1 to 1.5m).
• Remove the top layer of concrete (0.5 to 1m), as it is always compromised during underwater placement.
• The pipeline should not move underwater; the concrete must flow sideways, always beneath the previously poured concrete.