Lexington, KY – Concrete is everywhere. This might not seem like a very sexy topic, but wait until you’re about to invest a sizable chunk of change in a new concrete driveway. Then, if you want to understand what you’re paying for and get a good job done, the topic could suddenly turn pretty darn interesting.
Concrete is composed primarily of aggregate, cement and water. The aggregate is generally coarse gravel or crushed rocks along with a fine aggregate, like sand. Cement is a binder, a substance that sets and hardens independently, and holds the other materials together.
Cement manufacturing is a complicated topic. There are many different types, each with specific ingredients and manufacturing method. While homeowners don’t need to know about all of that, here’s something worthy of note: despite plenty of research, the process by which cement sets, when mixed with water –– called hydration –– is not completely understood, even though this material has been used since Roman times.
There are safety issues with this product. Bags of cement have warnings on them because cement is highly alkaline and it releases heat as it is setting. As a result, wet cement is strongly caustic and can cause skin burns if not promptly washed off with water. Dry cement powder can cause severe eye or respiratory irritation.
And now, let us consider your driveway. Even though a good pavement contractor will be knowledgeable and careful about your job, it never hurts to be an educated consumer.
The first step in your project, after the design work, is site preparation. Your existing driveway can easily be removed and carted away. If there is a gravel base, at least part of this can be reused. It will need to be compacted with a vibratory plate compactor.
Next, the side forms will be placed and securely nailed to stakes that should be no more than four feet apart. The forms will likely allow for a slab thickness of four inches, which is considered sufficient for a residential driveway. Isolation joints need to be installed wherever your new driveway will meet existing pavement. These joints are typically made by inserting pre-molded joint material along the edge of the existing pavement.
The concrete mixture is very important to the success of your project. There are many aspects to consider but here are three basics: cement content, water content and air content.
Cement comprises 10-15 percent of the concrete mix, by volume. The recommended minimum cement content is 564 pounds per cubic yard of concrete, often referred to as a “six bag mix,” since one bag of cement weights about 94 pounds.