TABLE OF CONTENTS
What is air entrainment in concrete?
Concrete Specifications & Air Entrainment
Prevention Against Cracking
Concrete Surface Finishing
Mechanism in Air-Entrained Concrete
Waterproofing with Air Entrainment
Sealing Air Entrained Concrete for Exposed Concrete
Summary of Blog Post
What is Air Entrainment in Concrete?
Air entrainment in concrete adds a percentage indication for air-entraining admixtures into concrete mixtures that provide small (tiny) air pockets in process/curing. Air-entrained concrete can be specified by an engineer in a specification for your home’s concrete, & delivered from the plant from which the concrete is being ordered. Adding air into the admixture of the concrete provide added durability for freeze-thaw (water intrusion), which may also help in preventing damage against salts/de-icing chemicals/sulfates, through increase of dissipating water but also losing a bit of curing strength.
Air entrained concrete is typical for a variety of outdoor mixes too, not necessarily structural in nature.
As concrete cures, pockets remain in the concrete structures/elements with an air-entraining admixture. This type of concrete is also generally more expensive than standard concrete. Some engineers might even increase the MPa (strength) of the concrete containing the admixture.
Photo Above: Concrete foundation walls such as the ones shown above typically can be provided an air range of 4 – 7% which will coincide with an exposure class on a table (concrete mix schedule or concrete design properties) for the given structural element.
Concrete Specifications & Air Entrainment
Air entrainment is a determination that an engineer or the project contractor can make. Generally, any of the concrete in a building that can be exposed to de-icing chemicals will also have to be air-entrained (admixture) for sulfate resistance, providing additional corrosion mitigation over time.
Concrete elements typically with air-entrainment for mix design: concrete foundation walls, grade-beam, pile capping (pile-caps), footings, concrete slabs etc.
In some cases, the specification for the concrete above the grade may not indicate that it is air-entrained due to a lack of concerns about exposure to significant freeze-thaw cycles, sulfates, or de-icing chemicals. Concrete mix designs and concrete mix table properties outline the air range for entrainment in various concrete mixes utilized throughout a project.
An example could be a suspended concrete slab in a building serving as a floor slab. It is protected from the exterior and not exposed to the elements and doesn’t necessarily need air entrainment. Furthermore, air entrainment may lead to a reduction in strength in some cases, which may not be desired for structural elements above grade.
Typically, the contractor makes the call based on the concrete schedule provided for the building (exposure classes).
Concrete design property schedules ultimately dictate air ranges for locations of structural elements like pile caps, grade beams, footings, slabs on metal decks, exterior slabs, interior concrete slabs, concrete patio slabs, and driveway/loading-dock concrete slabs.
Prevention Against Cracking
Likewise, where concrete is expected to be exposed to water and other liquid penetrants and freeze/thaw cycles, air entrainment provides durability (crack prevention) to some extent. Or at least, the likelihood, frequency, and severity of such events would be reduced from water, allowing expansion of water when freezing and reducing cracking/scaling prevalence.
For residential properties, air-entrained concrete can be ordered from the plant you are working with. Air-entrained concrete is delivered to the site, mixed in the truck, and ready to be poured. Talk to your Calgary concrete contractor about the exposure class of your concrete, with added waterproofing coatings on the exterior that are adequate to meet most residential specifications for concrete foundation work.
Concrete Surface Finishing (aesthetics)
Noteworthy is that higher air ranges of air-entrained concrete does not finish as neatly or smoothly as non-air-entrained concrete. It is harder to get a super lovely aesthetic finish with high air range air-entrained concrete. For finishes such as walls, interiors, slabs, or other architectural features, air entrainment could be omitted or minimized as best possible, subject to engineer’s guidance.
Structurally, as long as the minimum MPa requirements are being met then air entrained concrete is a non-issue strength-wise for your building or home.
A smooth interior slab finish, such as exposed concrete on the interior of a home may be difficult or near impossible to achieve with air-entrained concrete.
In such cases, the architect or engineers may specify a non-air-entrained concrete mixture to achieve a better fit and finish on the floor.
Talk to your concrete contractor about their capabilities when it comes to finishing air-entrained admixture concretes!
Mechanism in Air-Entrained Concrete
Mechanism-wise, the air-entrained concrete works with pores in the mix that allow migration/expansion and water movement, which dissipates trapped liquids from expanding during the winter and causing severe damage to the concrete foundation. This is in the case of freeze-thaw repetitive cycles, tiny air pockets in the concrete allow for migration of liquids.
If you are in the market for concrete foundation repairs in the Calgary area and need a professional foundation repair contractor, the Deluxe Concrete Solutions team can help you. They provide immediate Calgary foundation repair solutions for cracks, such as epoxy injection solutions, but also waterproofing systems that can help to replace and repair the waterproofing characteristics required of your concrete foundations.
Waterproofing with Air-Entrainment
Combination of air entrained concrete with waterproofing techniques is possible. While foundation coatings technically have a lifespan for the product applied, the addition of air entrainment with a concrete mixture lasts longer, as the feature freeze/thaw damage prevention is embedded within the concrete. There are many waterproofing products on the market these days, so if total sealing is your goal, identifying the correct product to match with your concrete mix design is needed. In some cases, services of a specialized waterproofing contractor may be warranted for both product selection and application.
If you have any concerns with drainage or a foundation weeping tile system, air entrainment will serve you well as the foundations and footings will regularly be exposed to water, and the prevention of structural damage due to freeze-thaw cycles is essential to ensure the structural strength of the concrete foundations.
Sealing Air Entrained Concrete for Exposed Concrete
If you are looking for a good-finish slab and protection against sulfates, salts, and other chemicals, concrete sealing solutions may suit you well.
Air entrained concrete with rougher finishes can be provided protection against surface stains, spills, and water for instance. Penetrating concrete sealers can serve well in this capacity, for architectural and landscape concrete in exposed concrete such as patios and landscape concrete.
Penetrating concrete sealing products can provide a base level of water resistance and increase durability of air-entrained surfaces like broom finish driveways and broom finish sidewalks.
In Summary
An engineer, architect, or experienced general contractor / concrete contractor generally determines concrete for mix design. Air-entrained admixtures are expected for below-grade or at-grade structural concrete exposed to elements or potentially exposed to water and freeze-thaw cycles.
Generally the mechanism by which air-entrainment protects concrete is by micro-bubbles of air pockets left in the cured concrete to allow for movement of water and expansion in the event of freezing. This prevents cracking and scaling, prolonging structural integrity of the concrete structural foundation walls, grade beams, footings, pile caps and more!
If you desire a high-aesthetic finish with your concrete, higher ranges air-entrainment is not suggested.
Any experienced concrete contractor will understand what this concrete is and where it should be used.
For your Calgary home concrete foundation requirements, call the team at Deluxe and let them take care of all the formwork, reinforcement, layout, placement, waterproofing, and mix design selection for you. They’ll also ensure that you have air entrainment where you need it throughout your project, acting as a liaison between you and your engineers/architects or general contractor to give you
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