How Can I Tell If My Concrete is Dry?
Concrete Curing
Concrete first cures before it dries. Curing is a process where crystalline fibres are grown. Addition of water is vital for this process to occur. As curing occurs the concrete hardens.
CaO / SiO2 /AL2O3 /Fe2O3 + H2O -> 3 CaO.2SiO2.4 H2O
Concrete can cure even if it is 100% submerged in water.
Concrete Drying
Once curing is complete, concrete must be thoroughly dried before additional floor coverings are laid.
A 100mm slab can take 4 months to dry. The humidity in the concrete needs to be less than 75%.
This prevents moisture damage to carpets, vinyl or wooden coverings. Sufficient drying of concrete is also important following any significant flooding events.
Excess moisture can result in bubbles forming under vinyl flooring, rot, cracking and warping in timber, and mould growth, especially when carpet is laid.
Concrete drying can be a lengthy process and – since the top layers dry first – a visual assessment often doesn’t reveal the moisture trapped below. Over time, this hidden moisture can migrate upwards, causing mould growth and damage to floor coverings.
Determining Concrete Moisture Content
Luckily, we have a simple, non-invasive method to check if your concrete is dry:
- Humidity Box Placement: Place a humidity box on any shaded area of bare concrete.
- Waiting Period: Leave the box in place for 24 hours. During this time, the air inside the box equilibrates with the moisture content of the concrete beneath.
- Measurement: After 24 hours, we take a humidity measurement. This process takes about five minutes per box.
- Results: Humidity measurements below 70% indicate that the concrete is dry enough to lay floor coverings.
What If My Concrete Isn’t Dry?
If your concrete isn’t dry, avoid using forced drying methods like heaters or dehumidifiers. These only dry the surface, leaving moisture trapped beneath. Instead:
- Protect from Elements: Keep your concrete protected from rain and flooding.
- Ventilate: Ensure good ventilation in the area.
- Drying Rule: As a rule of thumb, allow one month of drying time per 25 mm of slab thickness following laying and curing.
For more detailed advice and professional assessments, contact K2 Environmental to ensure your concrete is fully dry and ready for floor coverings