Concrete Driveway Paving 101: A Comprehensive Guide
Table of Contents
- Concrete Driveway Overview
- What is Concrete Made Of?
- The Unbeatable Strength of Concrete
- Benefits of Concrete Driveways
- How is a Concrete Driveway Installed?
- Decorative Concrete: A World of Possibilities
- Concrete Driveways: Bottom Line
Concrete Driveway Overview
Concrete has long been a popular surface covering for paving installations of all kinds, from major highways to residential driveways and everything in between.
With over 20 billion tons of concrete being put to use every year, it's safe to say that this classic building material has an enduring fan base!
There are many reasons for concrete's popularity: it's exceptionally strong, durable, versatile, and for driveway installations in particular, it is a surface covering that offers aesthetic appeal along with excellent functional value.
What is Concrete Made Of?
Before we go any further, it would be useful to find out what makes this extremely popular material so strong and durable.
Concrete is comprised of three basic "ingredients": Water, aggregate (often gravel, crushed rocks, or sand) and Portland cement.
Cement is actually a powdery substance that acts as a binding agent in the concrete mix.
As soon as cement is combined with the water and aggregate particles, the entire mixture transforms into a semi-solid "slush" that can be poured and manipulated to fill practically any form or shape you desire.
Once this mixture is poured, it will eventually harden into the material that we all know as concrete.
What's interesting is that not only is hardened concrete one of the strongest materials on earth, but as the years go by, it continues to get stronger and harder over time.
One excellent example is the colossal Hoover Dam – even though it was built more than 80 years ago, the concrete in this massive structure is still curing to this day!
The Unbeatable Strength of Concrete
Strength is one of the most prominent reasons why people choose concrete as a paving material for their driveway.
This robust material reaches an average compression strength of around 2,500 to 5,000 psi (pounds per square inch) but there are even some mixes that have a compression strength of up to 20,000 psi.
For the most routine uses (e.g. a driveway), a compression strength of 2,500 to 4,500 psi is typically used which is suitable for bearing the load stresses of most vehicles.
Your paving contractor will be able to tell you whether or not you will need a higher strength rating based on the type of loads that your pavement is intended to bear.
For example, if you're going to keep an RV or some other large, heavy vehicle parked on the driveway, more than likely your paving contractor will recommend a stronger grade of concrete or to increase the thickness of the slab.
In fact, increasing the thickness of a pavement slab by just one inch can increase its load-bearing capability by up to 50 percent!
Believe it or not, sometimes the biggest load stresses do not come from what's on top of the slab but from what's beneath it. Issues such as heaving (swelling due to the expansion of soil) from the subgrade can place incredible stresses on concrete slabs from beneath the surface.
This is why it's so important to make sure that you only choose a qualified and experienced paving contractor to install your driveway as it will be facing significant issues from both above and below.
Benefits of Concrete Driveways
Concrete lands somewhere in the middle of the scale in terms of cost – it's not the cheapest way to go, but it's also not the most expensive either.
While costs can vary based on a number of factors (including region), the general price range for a basic driveway installation will be somewhere between $4 to $10 per square foot.
As we have mentioned before, there are a number of variables involved in pricing a pavement installation but for the most part, the price range above represents a large percentage of concrete driveway paving jobs in terms of the all-in cost to get it installed.
Not only is this a reasonable and competitive up-front cost, but since concrete is a virtually maintenance-free surface covering, the long-term savings you can realize from choosing this paving material for your driveway can be quite substantial.
2. Long Lifespan
The reason why there's such a large variation in its expected age is because there are several important factors that contribute to the quality and durability of the pavement slab.
Variables such as subgrade quality, frequency and type of maintenance performed, drainage considerations, and weather/climate issues can all play a part in the long-term performance of your surface covering.
We hate to sound like a broken record here, but the quality of the actual installation is going to be one of the biggest factors that determine the lifespan of your driveway.
By getting your concrete driveway sealed every 5 years and by choosing a skilled paving contractor who pays close attention to detail and offers quality workmanship, your pavement stands a much better chance of remaining strong, resilient, and durable over the long haul.
3. Quality Appearance
A concrete driveway can provide plenty of "curb appeal" because it offers a neat, clean, and professional look that will complement your home's exterior.
First impressions do count, and a well-installed concrete driveway can provide a memorable one by adding more aesthetic appeal to your home.
4. Strength and Durability
As mentioned earlier, concrete is one of the strongest and most durable building materials on the planet.
The fact that there are concrete structures from the days of antiquity that are still standing today – many of which are still fully functional – is a testament to the unparalleled strength and durability of concrete.
For example, the Pantheon in Rome is a massive structure that was built in 126 A.D. and yet it still remains the world's largest unsupported concrete dome, comprised of more than 4,500 metric tons of Roman concrete!
Although nowhere near as grandiose as an ancient Roman temple, a driveway constructed of concrete can also provide decades of service life due to the outstanding durability of this highly popular building material.
Regardless of what type of exterior decor or landscaping you have installed around your property, concrete can complement a wide range of tastes and styles.
With their expert advice, you are sure to find a style of pavement that can match and enhance the look of your property.
How is a Concrete Driveway Installed?
It is important to note that properly installing a concrete driveway requires a lot of skill and specialized knowledge. Due to the many variables that are involved in mixing, placing and finishing concrete, it's a job that is best left up to a professional paving contractor.
You have to keep in mind that concrete installation is a very time-sensitive process since the material being installed is transforming from a semi-solid state to a solid state literally by the minute.
Without a proper understanding of the timing and quantities needed to properly mix and place concrete at the peak of its viability, you can end up with a huge mess on your hands. Not to mention that once the concrete is set into place, it's going to be extremely difficult to fix.
For this reason, it's a much better idea to go with a trusted and qualified paving contractor who knows how to expertly prepare, mix, and place the concrete for optimal strength and durability.
That being said, here is a basic overview of the steps that your contractor will take to install your concrete driveway:
1. Preparing the Subgrade
Subgrade refers to the actual ground upon which the pavement will be poured. There are some regions of the country where a contractor can simply pour the mixture right on top of the native soil because the composition of the soil allows for a direct overlay.
Other regions, however, have soil that is rich in clay or other types of minerals that expand when they come into contact with moisture, and this can pose a real problem for a paving installation.
Once the soil begins to expand, it can place tremendous pressure on the underside of the slab, creating all the conditions necessary for cracking to begin.
In fact, this is one of the main reasons why cracking in pavement occurs – if it was laid on top of a subgrade that is subject to soil expansion, it's only going to be a matter of time before the cracks start showing up.
So for those regions of the world where a direct overlay simply isn't possible, an additional layer of material known as a subbase will need to be installed before the area can be paved.
But before anything happens, the subgrade will still need to be leveled off and tightly compacted to ensure optimal stability and support for the subbase and slab that will go on top of it.
This can include removing loose rocks, leaves, tree stumps, and other vegetation that could cause surface irregularities.
Once the subgrade has been properly cleared and compacted, it will be ready for the next step.
2. Setting the Forms
The word "forms" refers to the beams of wood that are used to designate the shape and size of the intended driveway.
Much like the borders of a sandbox, the forms designate the outside edges of each side of the pavement, giving your contractor the much-needed parameters to begin the installation.
3. Installing the Subbase
The subbase is typically a layer of gravel that is laid on top of the subgrade to provide extra support for the soon-to-be-installed pavement. The thicker the subbase, the more weight the concrete slab will be able to handle.
So if the driveway is being designed to hold heavy vehicles (e.g. large trucks, RVs, etc), your paving contractor might recommend installing a thicker subbase.
One huge advantage of installing a subbase is that it can provide what's known as a "capillary break" to keep groundwater from seeping into the slab.
It's much easier for water to creep up into the slab via capillary action (i.e. the ability of liquid to flow into substances without the aid of external forces like gravity), when there's no barrier between it and the slab above it.
With a gravel subbase, however, water will have a much tougher time traveling through that thick layer of crushed rocks in order to get to the bottom of the slab.
The average thickness of a subbase layer will be around 4 inches for a concrete driveway but once again, this can be increased or decreased at the discretion of your paving contractor depending on the specific needs of your project.
4. Placing the Concrete
When your paving contractor "places" the concrete, that basically means that they're pouring the semi-solid mixture into the predetermined area and working it into place as it hardens.
This normally requires a crew of about 5-10 people (depending on the size of the concrete project), and because the consistency of the concrete mix is changing by the minute, precision and attention to detail are a must.
As the wet concrete begins to fill the forms, the paving crew will manipulate the mixture as needed to create a smooth surface that is as level as possible.
In this sense, the word "level" does not refer to being completely flat, as we know that there are many driveways that sit on a slope; it actually refers to having an even surface without dips, bulges, or other surface aberrations.
One of the biggest factors that your paving contractor will pay attention to is drainage. Without adequate drainage, your driveway can experience all kinds of problems due to ponding water or storm-water runoff heading in the wrong direction.
Nobody wants to deal with a garage or home that floods every time it rains due to an improperly graded driveway.
That's why your paving contractor will take great pains to ensure that your concrete driveway – from the subgrade all the way to the surface layer of the pavement – has been adequately graded to allow for optimal drainage.
5. Finishing the Concrete
The finishing process also helps to bring some of the finer aggregate particles to the top of the pavement, while pushing the rougher aggregate particles further into the slab.
This creates a smoother surface, along with achieving a better overall appearance.
Since concrete is a semi-liquid mixture when it is first placed, it will change in volume once it cures. Just like a sponge will usually shrink and become smaller when it's dry versus when wet, concrete can be subject to shrinkage once it dries as well.
A typical concrete slab will usually shrink to the tune of about one-sixteenth of an inch per 10 feet of pavement.
This is the reason why your paving contractor will intentionally put "control joints" (straight grooves) in the pavement – it allows this natural contraction to take place.
So when the concrete eventually dries and shrinks, the cracks can follow these pre-set joint lines instead of forming in unsightly places.
The curing process is a must for concrete to achieve its full strength. The exact amount of time it will take to cure will depend on several factors including the slab thickness, outdoor temperature, and the compression strength of the concrete.
Unfortunately, many unskilled contractors can sabotage the future strength and hardening of a pavement installation by not allowing the slab enough time to properly cure.
Once again, this demonstrates why it so important to choose an experienced and trustworthy paving contractor to install your new driveway.
Some people mistakenly believe that the concrete dries out completely during the curing process, but this is slightly inaccurate.
It might surprise you to learn that concrete takes a really long time to fully "dry out" as it undergoes a slow, ever-evolving chemical process that causes the mixture to continually get harder and stronger.
In fact, even 50 years after the installation has taken place, concrete still actually contains a tiny fraction of water within its composition.
This is why, as we mentioned earlier, the Hoover Dam is still undergoing the curing process even though the last sections of concrete for the dam were placed in 1935!
Decorative Concrete: A World of Possibilities
While standard plain gray concrete is still the most prevalent type of driveway installation, modern technology now offers you an expansive array of decorative concrete options that can create a more fitting and harmonious look to your home's exterior.
Let's take a closer look at each one:
* Stamped Concrete refers to a slab of pavement that has been stamped with some type of decorative design using a high-pressure mold.
Using stamped concrete, your paving contractor can replicate the look of some of the most popular paving materials including brick, cobblestone, field stone, and natural slate but in a much more cost-effective manner.
There are a wide variety of design options available including using bands, borders, or contrasting colors to add an eye-catching splash to your pavement installation.
Even if you already have a paved driveway, it is still possible to resurface your pavement with a stamped concrete overlay.
The number of patterns and textures you can choose from are virtually endless and with features such as powdered pigments.
* Stained Concrete is another attractive and economical option for homeowners who are looking to add some visual flare to their driveway. With a typical stained concrete installation, your paving contractor will apply the stains by hand once the concrete sets.
Using stains, your paving contractor can add a variety of bold accents or subtle hints of color that will penetrate deeply into the surface of the pavement, making them fade-resistant and impervious to peeling or flaking.
There are two basic types of stains that are commonly in use today: Acid-based stains and water-based stains.
Acid-based stains produce a chemical reaction with the concrete that creates a rich, unique and beautiful finish, but they are mostly limited to earth tones and other similar colors. Water-based stains, on the other hand, offer a wide variety of visually bold and vibrant colors.
Your paving contractor may also offer additional aesthetic elements such as faux or decorative finishing, stenciling, and/or decorative sawcutting.
Whether you choose stamped or stained concrete (or some combination of both), your paving contractor will help you review the many styles and color options available for your design needs and budgetary requirements.
With their help, you can transform your driveway into an amazing work of art!
Concrete Driveways: Bottom Line
If you've been thinking about getting your driveway paved (or even repaved) with concrete, enlist the help of Save On Paving.
We will connect you with only the best and most qualified paving contractors in your area, so that you can feel confident you'll get the ultimate results you're looking for. Contact us today to give your driveway – and the exterior of your home – a beautiful new look.
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