Module 5: Curing & Protection Methods for Concrete

1. Moisture Retention Techniques

Proper curing maintains hydration, ensuring strength development and durability.

A. Curing Compounds

• Types:

• Wax-based (most common)

• Acrylic/resin-based (for high-wear areas)

• Chlorinated rubber (for colored concrete)

• Application:

• Spray evenly (200-300 sq ft/gal coverage)

• Apply within 15 minutes after final finish

• Reapply if rain occurs within 4 hours

• Curing Efficiency:

• 75-90% moisture retention (vs. 100% with wet curing)

B. Wet Curing

• Methods:

• Continuous ponding (for flatwork)

• Wet burlap/geotextile mats (must stay saturated)

• Sprinklers (avoid thermal shock from cold water)

• Duration:

• Minimum 7 days (per ACI 308)

• 14+ days for high-strength mixes

C. Membrane Curing

• Polyethylene Sheeting:

• 6 mil minimum thickness

• Overlap seams 12" + tape seal

• Weight edges to prevent wind uplift

• Liquid Membranes:

• Spray-applied biodegradable films

• Used where sheet protection is impractical

2. Temperature Control Methods

Hot Weather Concreting (>90°F)

Best Practices:

• Pour early morning/nighttime

• Keep subgrade damp to prevent moisture theft

• Limit ambient temp differential to <35°F from concrete temp

Cold Weather Concreting (<40°F)

Heating Methods:

• Insulated blankets (R-value ≥3.0)

• Hydronic heating tubes (for slabs)

• Enclosures with forced-air heaters (maintain >50°F)

3. Form Removal & Loading Timelines

Formwork Stripping Times

(Per ACI 347 - Minimum Periods)

Critical Checks Before Removal:

• Field-cured cylinders test ≥500 psi (lateral pressure resistance)

• No live loads until 75% design strength

Safe Loading Times

(Assuming 70°F curing conditions)

Pro Tip: Use maturity meters (ASTM C1074) to verify in-place strength for early loading.

Curing Verification Methods

1. Pull-Off Tests (for membrane-cured surfaces)

2. Relative Humidity Probes (ASTM F2170)

3. Infrared Thermography (detect cold spots)