Top 6 Benefits of Using Exposed Aggregate Retarder for Driveways

Your driveway is an important part of your home’s outside design, and acts as the main entrance to your property for both vehicles and visiting pedestrians. The better-looking your driveway is, the more appealing your whole house will be.

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Exposed aggregate is one of Australia’s favourite materials for driveways, and using the right retarder is the key ingredient to a successful installation of an exposed aggregate driveway. Exposed aggregate retarder is a must-have component when installing these types of driveways, and this blog will detail six reasons why we think you’ll love its effect on your new driveway.

What Is Exposed Aggregate Retarder?

Before we dive into what we love about using exposed aggregate concrete retarders on your driveway, let’s define what this incredible chemical actually is:

Exposed aggregate retarder is a water-based, thick fluid that is applied to freshly laid aggregate concrete once any bleedwater has disappeared. It will often come in a variety of bright colours and may even change colours multiple times, such as it being one colour on the pail, a different hue when sprayed and another as it dries. These bright colours allow you to see exactly where the aggregate finishes and your concrete starts.

The retarder will slow the rate at which the upper layer of concrete sets while allowing underlayers to cure at their usual rate. Once the lowest sections of your aggregate concrete have set, the retarder can be washed away with water, at which point it will take away the upper layer of your concrete with it–exposing the beautiful aggregate stones for all to see.

Using an exposed aggregate concrete retarder for your driveway is the safest and easiest way to expose the stones you’re looking for. If you’re not using a retarder, you may need to use harsh chemicals or dangerous blasting instead, both of which can damage your driveway and prove difficult to achieve a uniform finish with.

Here are six benefits of using an exposed aggregate retarder when creating an aggregate driveway!

1. A Longer-Lasting Driveway

Your driveway is the last thing you want to be worrying about when it comes to household cleaning and maintenance, which is why using a retarder in its creation is such a good idea. Using a retarder when exposing the aggregate creates a uniform concrete surface, with every piece of aggregate secured in place.

This means your beautiful exposed aggregate concrete driveway will be less likely to lose stones, crack or warp due to factors like an uneven surface or over-exposed stones. Fewer problems equal less stress in performing fixes or hiring professionals, and you can enjoy a perfect aggregate driveway for many years to come!

Want more information on what can happen if you don’t use a retarder? Check out the appropriate section in our blog on Understanding the Role of Exposed Aggregate Retarder in Concrete Works.

2. Better Grip On Wet Days

Slippery driveways can make using your car on a wet or icy day dangerous and difficult, with the potential for sliding high on smooth, traction-free driveways. When you use a retarder to create your aggregate driveway, you are instead creating the perfect driveway surface that your car can grip onto in all sorts of weather thanks to its excellent slip resistance.

By exposing the aggregate at an even rate using a retarder, you create a textured driveway that your vehicle’s tyres can easily hold onto. This can also be helpful when walking on your aggregate concrete driveway when it is wet or icy, as the even aggregate will keep you from slipping over and injuring yourself.

3. Easy To Clean

Concrete surface driveways tend to accumulate all sorts of natural and man-made debris, from dirt and leaves all the way to oils and food stains. If you’ve exposed your aggregate surfaces using harsh chemicals or blasting techniques, then you may find dirt and debris hiding inside uneven patches of the driveway or holes left by dislodged pieces of aggregate, which can hinder your cleaning processes.

By using an exposed aggregate retarder, you can create an even driveway with just the right amount of exposure for the aggregate pieces. This means fewer cracks and crevices for dirt to hide, making it easy to sweep or hose your driveway clean when needed.

To further protect your aggregate driveway and make it resistant to stains, apply a quality concrete sealer that will help it repel water and oil, brighten the colours, and give it a satin or gloss sheen!

Read our blog on Maintenance Tips for Exposed Aggregate Concrete for more information on keeping your aggregate looking its best!

4. Customisation Options

There are many options when it comes to choosing the type of aggregate finishes you want in your driveway–natural stones are the most common, but glass, shells and gravel are also options you can choose to suit your home’s design. By using a retarder to expose the textured surface you ensure that your aggregate stays in one piece, even delicate ones that would otherwise shatter if exposed using blasting techniques.

By using a retarder, you are making sure you have plenty of options when it comes to decorating your driveway. Match aggregate colours and materials with your home’s embellishments and materials for a coordinated look, or go for a bold material that stands out from the rest of your property! Either way, using a retarder is the best way to ensure your driveway looks as good as possible.

5. Curb Appeal & Value

A beautifully crafted aggregate driveway can become the highlight of your home’s outside facade, and using an aggregate retarder is the best way to ensure your driveway turns out perfectly. 

An aggregate driveway that has been crafted without a retarder may have overly-exposed stones that are unpleasant to walk on, collect dirt around them and are more prone to damage, like cracks or even total dislodgement. Or if the aggregate surfaces haven’t been exposed enough, you may not be able to see the beautiful stones and chips at all.

By using a retarder, you ensure your aggregate driveway will look its best for years to come and is always easy for a quick clean, making it easy to prime and prep if you ever decide to sell your property to potential buyers, or just want to welcome guests with an attractive front driveway.

Learn more about the finishes available for aggregate driveways in our Why Exposed Aggregate Retarder is Essential for Perfect Finishes blog.

6. Eco-Friendly

Choosing to expose the aggregate elements in your concrete driveway using a retarder is not only an easy choice, but it’s also an eco-friendly one. Using strong, harmful chemicals to expose your aggregate means they will be pushed into your garden and local waterways when you wash them off, which can potentially cause harm to vegetation and creatures in the area. Blasting techniques will also cause concrete wastage that contributes to landfill.

The range of aggregate retarders at Australian Slate-Crete Supplies are water-based and don’t contain any harsh or dangerous chemicals, which means when you wash them off at the end of the curing process, you don’t need to stress about your environmental impact. Use them to beautify your driveway and feel guilt-free about impacting the environment at the same time!

Need more convincing? Make sure to check out our blog on Is Exposed Aggregate Concrete the Right Choice for Your Driveway?

Trust Aus Slate-Crete Supplies For Quality Aggregate Concrete

Have you decided to use an exposed aggregate retarder for your driveway? Browse the wide range at Australian Slate-Crete Supplies, the best source of exposed aggregate supplies in Melbourne, and enjoy a great range of high-quality products you can utilise on your property!

If you are looking for more details, kindly visit retarder in concrete.

What is Concrete Retarder?

Retarders are additives that slow the setting of cement paste and, by extension, mixtures like mortar or concrete that contains cement. Concrete retarders are also known as retarding admixtures or just retarders. Adding a retarder to the concrete mix can delay the setting time by up to an hour. They slow the hardening process in warmer weather to give workers more time to mix, transport and place the concrete. Retarders not only slow down the process, but they also save water.

Fig 1: Concrete Retarder
Courtesy: concretechemicals.home.blog
Mechanism of Retardation:

The hydration reactions are momentarily halted by dissolving a retarder in the mixing water or spraying it on the concrete’s surface, resulting in a longer resting period. The mechanisms that develop themselves are influenced by the specifics of the retarder and cement used. It’s also important to know that the things that cause retardation are only there for a short time. After a set amount of time, the mechanisms stop working, but the watering continues. The following are the four mechanisms of retardation:

i) Adsorption:
A retarding additive is deposited onto the cement particles’ surfaces. The retarding admixture forms a Protective skin around the cement particles. Because of this diffusion barrier, water molecules have a harder time reaching the surface of the unhydrated cement particles, slows down the hydration process. As a result, the cement paste retains its plasticity for longer because there are not enough hydration products to make it hard. This retardant additive reacts with the cement’s C3A, comes out of the solution, and is mixed into the hydrating substance.

ii) Nucleation:
In response to the presence of water, the cement particles’ surfaces expel calcium ions and hydroxyl ions. The hydration products C2S and CS crystallize once the concentration of those ions reaches a threshold value. As the cement cures, the nuclei of calcium hydroxide adsorb a retarding admixture, which inhibits further nucleation until the cement reaches super saturation.

iii) Complexation:
During the first few minutes, calcium ions released by the cement grains form some complex with other ions. When these complexes form, they make the cement easier to dissolve. In the aqueous phase of the cement paste, the concentration of Ca 2+, OH-, Si, Al, and Fe will go up during the hydration process if a retarding admixture is present. The buildup of calcium and hydroxyl ions in the solution stops the calcium and hydroxyl ions from clumping together to form calcium hydroxide, slowing the hydration process.

iv) Precipitation:
In precipitation, the retarder reacts with the extremely alkaline solution to generate insoluble derivatives. This process is quite similar to adsorption. When water and cement come into contact, the pH of the solution quickly climbs to over 12 within the first few minutes. Protection layers of these insoluble compounds precipitating around cement particles inhibit hydration. The coating prevents water molecules from making excellent contact with the cement particles by acting as a diffusion barrier.

Types of Concrete Retarders:
1. Organic Retarder:
i) Phosphonates
ii) Lignosulphonates
iii) Sugars
iv) Hydroxycarboxylic acids and their salts

2. Inorganic Retarder:
i) Salts of Pb, Zn, Cu, As, Sb
ii) Borates
iii) Phosphonates

How Retarding Additives affect Concrete’s Properties:

Fig 2: How Retarding Additives affect Concrete’s Properties
Courtesy: civilscoops.com

1. Strength:
When applied to concrete, retarding admixtures reduce the initial compressive strength relative to untreated concrete.

2. Slump Loss:
The use of retarding admixtures has been shown to greatly improve the initial workability of concrete by decreasing slump loss.

3. Durability:
It is expected that retarded concrete when properly cured, will have the same durability as ordinary concrete of the same volume.

4. Workability and Rheological Values:
The workability of concrete is also marginally affected by retarding admixtures. They can lead to a 60-100mm more initial slump.

5. Volume Deformation:
The addition of retarding admixtures does not significantly alter creep or drying shrinkage, although it may increase plastic shrinkage.

6. Air Entrainment:
Most retarding admixtures do not bring in air, but some do. Especially those based on Hydroxycarboxylic acid, which can reduce air content.

7. Bleeding:
The use of retarding admixtures always increases the risk of bleeding in concretes.

8. Freeze-Thaw Cycles:
Air-entraining admixtures are frequently used to increase the concrete’s resistance to freezing and thawing. The air cells act as tiny expansion chambers for the freezing water after being frozen in the concrete.

9. Heat of Hydration:
While retarding admixtures does not diminish concrete’s heat production, they do delay the peak temperature rise by an amount of time equal to that by which the concrete was retarded.

Uses of Concrete Retarder;

• Most of the times, retarding admixtures are added to concrete when it is hot outside.
• Spraying a retarder on the surface of the formwork stops the matrix from hardening where it meets the formwork. On the other hand, the rest of the concrete gets hard.
• When building something big or very big, people use retarders.
• Admixtures that reduce the reaction rate are utilized during the grouting process for oil wells.

Advantages of Concrete Retarder:

• Concrete’s workability and cohesion are preserved by retarding admixtures, which also lengthen the time it takes to set.
• The use of concrete retarders can mitigate the dangers of long-distance delivery in hot weather by offsetting the hastening effect of high temperature on the initial setting time.
• Concrete retarder is used to delay the hardening of concrete between pours and prevent the formation of cold joints in major building projects.
• When poor sand grading is unavoidable, concrete retarders can be used to lessen the amount of segregation and bleeding that occurs.
• By delaying the setting time and increasing the workability of concrete, retarding admixtures enhances permeability.

Disadvantages of Concrete Retarder:

• Using water reducers with concrete retarders is possible, but curing must be monitored closely to prevent bleeding and fissures.
• Gypsum can delay concrete setting, but only if the process is well monitored and managed; otherwise, too much gypsum could lead to undesirable expansion and an endless delay in a concrete setting.
• Depending on the cement’s water-cement ratio, cement content, and C3A concentration, the appropriate dosage of retarding admixtures must be determined.
• Concrete retarders may have varying effects on various cement varieties in differing concentrations.

Conclusion:
Concrete retarders are a mixture that slows down the chemical process of hydration so that the concrete stays soft and is easy to work with for a long time. Retarders are used in hot climates to counteract high temperatures and speed up the process of establishing concrete’s properties.

It’s useful for keeping the consistency of concrete workable in hot weather, through challenging putting conditions, during lengthy transportation, etc. However, it is strongly suggested that trial mixes with the real cement used in the construction should be evaluated before applying a retarder. A mistake during construction might lead to wasted time and money.

References:
1. Ballieu, Pieter. “(PDF) Concrete Setting Retarder Mechanism | Pieter Ballieu – Academia.edu.” (PDF) Concrete Setting Retarder Mechanism | Pieter Ballieu – Academia.edu, www.academia.edu//Concrete_setting_retarder_mechanism. Accessed 11 Oct. .
2. Pvt. Ltd., NBM Media. “Effect of Usage of Admixture in Concrete.” Effect of Usage of Admixture in Concrete, 1 Dec. , www.nbmcw.com/product-technology/construction-chemicals-waterproofing/concrete-admixtures/effect-of-usage-of-admixture-in-concrete.html.
3. “All House Related Solutions – GharPedia.” All House Related Solutions – GharPedia,
gharpedia.com/blog/concrete-retarders-pros
cons/#:~:text=With%20the%20use%20of%20concrete,and%20improved%20workability%20of%20concrete. Accessed 11 Oct. .
4. “What Is Retarder in Concrete?” Real Estate Forum by NoBroker.com, 25 Aug. , www.nobroker.in/forum/what-is-retarder-in-concrete.
5. Team, Dream Civil. “Concrete Retarder | Types, Effects, Uses and Cost of Concrete Retarder.” Dream Civil, 2 Dec. , dreamcivil.com/concrete-retarder.
6. https://www.concreteconstruction.net/how-to/materials/retarders-for-concrete_o. www.concreteconstruction.net/how-to/materials/retarders-for-concrete_o. Accessed 11 Oct. .

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