Many people without any construction knowledge confuse cement with concrete and mortar. But cement is the vital binding material that keeps these more complex materials together. Basically, mortar combines cement, sand, sometimes lime, and water, and is used for brick- and block laying. A similar mix is used to render walls and screed floors. Concrete adds crushed stone to the mix and is used for all-important foundations and floors.
While there are a few basic types of cement, there are many other types that engineers specify for more complicated operations and projects involving heat, water, and other challenges.
Why Is It Important to Use the Right Type of Cement for Your Job?
Different types of cement have different properties, advantages, and uses. If you’re doing a DIY project at home, you can go and buy a bag or two of ordinary Portland cement (OPC) and you’ll be fine. But specialists who specify materials for more complicated projects will need to take construction and code requirements into account.
It all depends on the project.
Strength is all-important. General-purpose cement will reach its normal strength more quickly than high-performance cement. So, if you are building structures from pre-stressed concrete that must be water-tight, it will be essential to wait longer for it to reach its maximum strength. If not, it doesn’t matter.
Using the wrong type of cement can result in the failure of your entire project. This is why we use highly trained engineers who understand the intricacies of different types of cement to specify materials in the construction industry.
Types of Cement Used in Construction and Elsewhere
ASTM International, which used to be called the American Society for Testing and Materials, develops and publishes the standards for many technical things. These include those for cement.
It recognizes 5 main categories of cement, even though there are numerous variations that fall into their categories. This is not to complicate issues, but rather to help anyone working in the construction and civil engineering industries identify the types of cement they need for their projects. It all depends on the ingredients used to manufacture the cement.
OPC has a history that goes back to 1824 when an Englishman, Joseph Aspdin, patented a process to make a now globally-proven material used to bind building materials together. He made it by grinding together limestone and clay or limestone and shale. It looked like Portland stone found on the Isle of Portland, so he called it Portland cement.
That was nearly two centuries ago, and now there are so many different types of cement it’s difficult to keep track. We are going to start with OPC and then show how the varieties provide additional value.
OPC is a general-use material that is commonly used as the mortar that we use to lay bricks, blocks, stone, and other building materials. It holds these materials together and allows us to build walls and other structures. When it cures and dries, it forms the strongest possible structure we can imagine.
There are several variants of so-called ordinary Portland cement that have air-entraining materials mixed into the cement. This makes the cement even more resistant to damage from moisture.
This type of cement is used when there is an issue with water or soil that contains moderate sulfate, or when a build-up of heat is a concern. More specifically, Type 2 cements are used for structures in water or soil containing moderate amounts of sulfate, or when heat build-up is a concern.
Type 3 is a high early strength cement that hardens much more rapidly than other types of cement. What it means is that when it is used in a concrete mix it will quicken the process that normally takes a month to get to full strength.
When it isn’t a good idea to have too much heat during a construction process, low-heat Portland cement is the best option. It radiates less heat while it sets and dries.
Type 5 is a sulfate-resistant Portland cement that can be used when the soil or water is high in alkali.
How to Choose the Right Type of Cement for Your Job
While the ASTM categories are useful, it also helps to know in more general terms which is the right type of cement for your job. These include white cement, water-repellent cement, low-heat cement, and rapid-hardening cement. You need to know what your job demands.
Here are some examples.
This is the cement that we use for everything from DIY to most construction projects. It’s the cement you will find in your local hardware store.
This type of cement is similar to Portland cement but it is a lot more expensive. It is white, not gray, and is often used for upmarket architectural features.
If you are working on a project that relies on the retention of water or a structure that will be in constant contact with water, you are going to need cement that repels water, Usually, this will be an ordinary or rapid-hardening cement that is combined with a very small percentage of metal stearates like calcium or aluminum.
Project examples include anything and everything from tanks, swimming pools, and reservoirs, to bridges, piers, and retaining walls.
This type of cement doesn’t generate a lot of heat when it reacts to water and so it gains strength very slowly. It is commonly used when the soil has compounds that contain high levels of sulfate or alkali. Typically, this relates to groundwater, sewage systems, and coastal piers and platforms.
The reason to choose this cement type is simply to avoid the degeneration sulfates may cause.
This type of cement is useful when less water can be used to ensure that it sets. It is often used to build dams, the feet of turbines, and for large footings or raft concrete slabs.
High-alumina cement has a low pH that makes it incredibly resistant to chemicals including sulfuric acid. It is a good option for marine and sewer construction.
OPC mixes that have hydraulic and other special properties include IL (Portland-limestone), IP (Portland pozzolana), IS (Portland-slag), and IT (ternary blended) cement. IS is also known as slag cement and is often used in specified concrete mixes. These are generally impervious to water and set quickly.
While hydraulic cement is generally strong and resistant to rust, it doesn’t do well in colder temperatures.
Similar to Portland cement, rapid-hardening cement contains more tri-calcium silicate that is finely ground. This gives it a lot more strength at an early stage – three days vs. about a week.
The main advantage of using rapid-hardening cement is that formwork can be removed earlier. This makes it a popular option for prefabricated concrete construction projects as well as some roadworks.
If you don’t want your mortar or concrete to shrink while it hardens, the answer is to use expansive cement in your mix. This type of cement will often incorporate things like calcium sulfate and sometimes tricalcium.
This type of cement is valuable in areas when the water in concrete freezes. It creates billions of tiny air bubbles that enable the concrete to expand. But it isn’t a high-strength cement and should only be used when temperatures are very low and special deicing chemicals are specified.
If you imagine that cement is simply a gray powder that we use in the construction industry to build structures, you’re right. But not all types of cement are the same. In this article, we highlight the differences and show why it’s so important to use the right cement for the job at hand.
While OPC is absolutely fine for the vast majority of jobs, it’s not what you will need in many other construction situations. Anybody working in the construction or related industries knows (or should know) what types of cement they should use.
Our article summarizes the five main types of cement recognized by ASTM International. It also highlights the various different types that are used in specific instances. These range from projects where there is a need for rapid-hardening cement to scenarios where water is a major challenge.
Knowing that there are so many different types of cement will help anyone in the building industry, even those who aren’t qualified as engineers.