If you’ve ever wondered, “What is the difference between concrete and cement?” you’re in luck.
The terms concrete and cement are often used interchangeably. But the truth is, they are not the same. In fact, that “cement” truck many of us refer to on a job site is actually a misnomer—it is really a “concrete” truck.
As part of our efforts to spread knowledge about all things concrete, we are taking a closer look at the concrete vs. cement battle to set the record straight about these two commonly-used materials.
Concrete vs. cement: What is the difference?
Let’s start with the cement basics.
Cement is a binding agent which is used to join various materials together during the construction and building process. It is an ingredient in concrete (but not the same thing as concrete). Cement is made of materials rich in calcium and silica, such as limestone and clay. It is very adhesive, but it is also prone to cracking (which is why it isn’t used very often as a standalone material).
There are use cases for cement by itself, but typically for smaller jobs. The most common projects calling for cement are grouting, some masonry jobs, and concrete repair (where cement is used to fill cracks or repair crumbling in a larger concrete structure).
The most common type of cement is Portland cement. It is the type of cement used to make concrete. Portland cement is usually comprised of limestone, sand or clay, bauxite, and iron ore. It may include other materials such as shells, chalk, shale, or slate.
The various ingredients are mixed and heated to an extremely high temperature (ranging from 2,700 to 3,000 degrees Fahrenheit) in a cement processing plant (or more specifically, a cement kiln). The end product is an extremely hard substance called clinker, which is ground down to a fine powder and packaged. When clinker is mixed with water, a paste forms. This paste is used as a binding agent, and it holds together whatever it has been applied to as it dries.
There are five types of Portland cement:
- Type I is used for most residential work that doesn’t require any special qualities or properties.
- Type II is somewhat resistant to sulfate, and it is the most common type used in North America. (Note: Sulfate contributes to the deterioration of concrete.)
- Type III has a higher strength early on than Type I, making it easier to remove forms sooner. It is often used when there is a risk of freezing.
- Type IV has a low heat of hydration. It increases in strength at a slower rate. It is often used in large construction projects and industrial applications.
- Type V develops strength at an even slower rate and is used when severe sulfate resistance is required.
Now, let’s turn our attention to concrete.
Unlike cement, concrete is a building material. As we mentioned, concrete contains cement, comprising about 10 to 15 percent of the basic concrete mix. The other primary ingredients are sand, water, and stone/gravel. Other fine and coarse aggregates are also added to the mix depending on where and how the concrete will be used. The water in the concrete mix activates the cement and creates a binding agent between all of the other aggregates in the mix.
Though you may not consider this an ingredient, there is also air in concrete mix, referred to as air entrainment. These tiny air bubbles allow excess water to expand during the freeze/thaw cycle. If the air bubbles are too large, however, the excess water becomes entrapped, and the concrete will shrink and then crack.
Now that the difference between cement and concrete is clear, you can see that when we refer to a cement sidewalk or a cement mixer, technically, we are wrong. The correct terms would be a concrete sidewalk and a concrete mixer. There is cement in the sidewalk and the mixer, but that is not the only component.
Concrete basics: What are the qualities of good concrete?
There are several qualities that characterize a quality concrete mix that will deliver a long-lasting end product that requires minimal maintenance. Three stand out to us as critical to evaluate during the selection process.
Strength
We all consider concrete to be a strong and durable material, but all concrete is not created equal. There are actually different ways to measure concrete strength, including compressive strength (the ability of concrete to withstand loads that will decrease the size of the concrete), tensile strength (the ability of concrete to resist breaking or cracking under tension), and flexural strength (the ability of concrete to resist bending). Certain types of strength may be more important than others on a given project.
There are also several factors that contribute to the strength of a given concrete, including the water/cementitious ratio (a lower water-to-cement ratio makes concrete stronger), the proportioning of the concrete mix ingredients, mixing time, and curing methods. We dig into all of these concrete strength factors in another article, but the point is it’s important to carefully weigh the strength properties of a concrete mixture when selecting one for your construction and building projects.
Workability
Workability describes how easily the concrete can be placed. Some jobs demand a pumpable concrete or the concrete may need to be placed in hard-to-reach places. These types of scenarios make workability increasingly important.
Workability is closely tied to the amount of water used in the concrete mix. When you use less water, the concrete is stronger, but it also makes it harder to work with. If you’re unable to get the concrete in place properly, it doesn’t matter how strong it is.
That’s why it’s important to find the right balance between strength and workability when selecting the ideal concrete mix for a given project.
Resistance to freeze / thawing and water impermeability
These two qualities are very closely tied together, so we are combining them for the purposes of our discussion. Water expands when it freezes. When this happens inside moist concrete, it creates pressure, which can cause expansion and cracking. Once this happens, the concrete continues to become more damaged over time as more cracking and crumbling occurs.
Deterioration of concrete can begin in as little as 28 freeze/thaw cycles. Deicing chemicals can make freeze/thaw damage even worse, as the salt in these mixtures absorbs moisture and makes the concrete more saturated.
The more impervious concrete is to water and moisture, the more durable your structure will be and the longer it will last. Maintenance costs will also remain lower.
The future of concrete: Why Ultra High Performance Concrete raises the bar
Thanks to advancements in concrete technology, a more advanced version of concrete is now available—one that is stronger, more durable, and freeze/thaw resistant. This revolutionary concrete, called Ultra High Performance Concrete (UHPC), is actually similar to traditional concrete in many ways.
Approximately 75-80 percent of the ingredients in UHPC are the same as regular concrete—cement, sand, and water. The remaining 20-25 percent of the ingredients are what make it unique. Integrated fibers made from materials such as polyester, fiberglass bars, basalt, steel, and stainless steel are added to the mix to create a progressively stronger end product. The addition of steel and stainless steel deliver the greatest gains in strength.
UHPC excels in all three of the qualities of good concrete we just discussed, making it a better choice for construction projects.
- Strength—Whereas regular concrete has a compressive strength of 4,000 pounds per square inch (psi), UHPC has a compressive strength of 30,000 psi once fully cured. Some UHPC mix techniques can achieve even higher psi ratings.
- Workability—Many UHPC mixes don’t fit the bill when it comes to workability. Our proprietary UHPC mix, however, has a working time of more than an hour. It is also flowable (and pumpable!), which allows workers to use standard machinery such as a ready mix truck without any problems. In fact, Cor-Tuf UHPC can be used with all standard concrete equipment. It can be mixed, transported, and poured the same way as traditional concrete. Your team doesn’t need to learn any new techniques or tools, but the end product is stronger and more durable.
- Freeze/thaw resistance—UHPC has a higher density than traditional concrete, making it virtually impervious to water. The material does not deteriorate when exposed to deicing chemicals or sulfates. Studies have shown that UHPC can withstand more than 1,000 freeze/thaw cycles, making it highly superior to regular concrete.
There are a myriad of other benefits of UHPC over traditional concrete, including a lower carbon footprint, low-impact design, flexibility, impact resistance, and cost savings. We have conducted many tests on our own Cor-Tuf UHPC so you can see in action the amazing benefits of this revolutionary UHPC mix. We invite you to take a look at our gallery to get a closer look at the work we have done.
As you plan your next construction project, it’s important to know the distinction between concrete and cement. It’s even more important to be aware of the advantages to be had when you choose ultra high performance concrete over traditional concrete. We will continue to keep you updated on advances in UHPC, particularly in our proprietary UHPC mix that easily outperforms conventional UHPC mixes.
