Concrete guide / After the concrete is poured
Concrete curing vs drying: what each tells you
Curing protects the moisture and temperature conditions that help new concrete gain strength and resist damage over time. Drying is moisture leaving the concrete. A slab, such as a concrete floor or patio, can look dry before it is ready to carry a load or receive a floor covering.
See the three things to check01 / What the words mean
Curing and drying do different jobs
Curing
Help concrete gain strength
The cement in concrete reacts with water. This reaction is called hydration. It helps the concrete harden and gain strength.
Curing keeps moisture in the concrete and controls its temperature to support this reaction. It requires care as well as time.
Drying
Let water leave
Some water in concrete can turn into water vapour and leave through the surface. This is called evaporation.
The concrete mix, slab thickness and surrounding temperature and humidity affect drying. Humidity means the amount of water vapour in the air. A dry-looking surface does not show the moisture conditions inside the slab.
The Concrete Society explains curing and drying as different processes. Faster drying does not mean better curing: early moisture loss can remove water needed for hydration.
The National Ready Mixed Concrete Association (NRMCA) explains curing care in CIP 11: Curing In-Place Concrete. Follow the written curing plan for your project. This guide cannot tell you which method to use or when to stop.
Does strength gain stop when curing care ends?
No. The period of planned curing care and the time over which concrete gains strength are different. The American Concrete Institute (ACI) explains that concrete can keep gaining strength when moisture and temperature conditions remain suitable. Ending the specified care does not mean every chemical reaction has finished, or that the slab is ready for every use.
02 / Ask the right question
Check each next step on its own
First ask, “What do I want to do next?” Each step needs its own checks. Ask the builder or person in charge of the work what is needed.
When can curing care stop?
Check the written project plan and the curing-product instructions. Agree who will provide the care, how it will be recorded and who can confirm it is complete.
When can the slab carry a load?
A load is weight on the concrete, such as a car or stored building materials. Tell the project designer or builder which load you have in mind. Ask what strength evidence and approval are needed before placing it.
When can flooring or a coating be installed?
Check the instructions for the exact floor covering, coating and adhesive you will use. A coating is a layer applied to the surface. An adhesive bonds the floor covering to the concrete.
Find out which moisture test is required and what results the manufacturer accepts. Also check how the concrete surface must be cleaned or prepared.
NRMCA's guide to concrete slab moisture explains why moisture testing matters before installing floor finishes. Follow the current test requirements and product instructions; this overview does not replace them.
Check that the products work together
Some curing products leave material on the surface. Before pouring, ask if this will work with your planned floor covering or coating. Check whether it must be removed first.
03 / Use it in a project
Example: a garage slab with a bonded coating
Imagine that you are planning a new garage floor. You want to store building materials on the slab before applying a coating, then park a car on the finished floor. These are separate steps. Approval for one does not automatically approve the others.
Use the following as a planning checklist, not a construction specification. Replace each description with the records for your actual project.
- Concrete and curing plan
- Ask the builder for the specified concrete, curing method and completion requirements. Keep a record of the care provided and any problems, such as interrupted protection.
- Approval for the intended load
- Record which materials or vehicle will be placed on the slab. Ask the responsible designer or contractor to identify the evidence required and confirm when that load is permitted.
- Exact coating instructions
- Keep the manufacturer's current product sheet. Identify its concrete-age requirements, moisture-test method, acceptable results and surface-preparation instructions. Check compatibility with the curing product.
- Moisture report and installation decision
- Keep the test method, results, units, locations and date. Ask the installer to check the report against the coating instructions and confirm that the other installation requirements are met.
If a check fails: suppose the slab has been approved for storing the specified materials, but its moisture result is outside the coating manufacturer's limit. Keep coating installation on hold and agree the next step with the supplier and installer. The loading approval does not cancel the moisture requirement.
After the coating is applied, follow its own instructions for when the finished floor can be used. Concrete readiness and coating readiness are separate checks too.
Not sure how to buy the concrete? The ready-mix versus bagged concrete guide compares concrete delivered by truck with concrete you mix from bags. For a fence post, use the quick-set fence-post guide to check the instructions for your exact product.
How much concrete do you need?
Enter the specified length, width and thickness in the slab calculator to estimate the concrete volume. You can add a separate ordering allowance, meaning extra concrete you choose to order, and enter a price for the concrete itself.
It does not tell you how long curing or drying will take, or when the slab is ready to use.
Estimate slab concrete