The major differences between cement, concrete, and mortar are their ingredients and specific uses. This HomeQuicks article gives the comparison of concrete vs. cement vs. mortar, which includes all aspects like their composition, uses, and properties.
Did You Know?
Concrete is used in missile launch pads because of its fireproof nature.
Cement, concrete, and mortar are common terms one gets to hear during any construction or repair activity. Still, for the common man, there is a lot of confusion between the three. While cement is the starting material for both concrete and mortar, the latter two have their own niches in the construction business.
While concrete can be used independently of the other two to build strong and long-lasting structures, mortar is used as a ‘glue’ to hold together different bricks while building a wall. But neither concrete nor mortar can be produced without using cement in some quantity. It is concrete which is the strongest, on comparison.
All three materials have different strengths and properties, which helps decide where they should be used. Cement undergoes chemical changes when mixed with water to form a hard structure. This is the main reason why it is used for making both, concrete and mortar. This chemical transformation of cement helps bring out the strengths of the other two materials. When looking at the comparison of cement vs. concrete vs. mortar, it’s vital to consider their major differences, such as when to use them.
Cement vs. Concrete vs. Mortar
Cement is a powdery ingredient of both concrete and mortar, and is made up of lime, silica, alumina, iron, and gypsum.
Concrete is made up of cement, sand, water, and some coarse aggregate such as rock chips, pebbles or crushed stone.
Mortar consists of a binding agent, sand, water, and lime. The binding agent is generally cement, though slaked lime may also be substituted. Mortar differs from concrete, in that, it does not contain any coarse aggregate.
Cement is manufactured in two steps. First, all the ingredients like calcium oxide, iron oxide, alumina oxide, and silica oxide are obtained in bulk. They are crushed to a homogenous size and heated in a rotary kiln at a temperature of 2,000°C. The products obtained in this step are large grains called clinkers. Additional ingredients like gypsum and fly ash are added to this, which is then crushed in a cement grinding mill to obtain cement in a fine gray, powdery form.
Concrete is manufactured at a concrete ready-mix plant. First, aggregates like pebbles or crushed stone are coated with cement paste in a continuous mixer. If fibers are desired, they can be added now using different methods like hand-mixing or impregnating. The concrete is then transported to the construction site in a mixer truck.
Mortar is generally prepared by on-site workers themselves, by mixing dry Portland cement with lime, and then adding water. This is because, mortar once made, begins to cure in a very short time.
Lime mortar, on the other hand, is produced by heating limestone in a kiln to obtain quicklime. This quicklime is mixed with water to give slaked lime. Slaked lime, either in the form of a paste called lime putty, or hydrated lime powder, is finally mixed with sand and water to form the mortar.
Cement undergoes a chemical reaction when mixed with water, called hydration. This involves formation of a hard, interlocked, crystalline structure, which gives cement its high strength. The reason gypsum is added to cement is to increase its ‘setting’ time, thus allowing for a longer working time.
When concrete is mixed with water, the curing process begins. The cement particles in concrete absorb water and undergo hydration. Because of this, hard, crystalline bonds are formed in the cement which trap or interlock the aggregate particles within its structure. Before the process is completed, the concrete is poured into a mold to give it a final shape on setting. Adequate moisture content is vital for hardening to occur well.
Similar to concrete, mortar hardens when the cement in it undergoes hydration, trapping the sand particles in hard bonds. Lime mortar, on the contrary, hardens when it is exposed to air. The calcium hydroxide in the mortar absorbs carbon dioxide from the air to form hard, solid calcium carbonate.
► Cement is a homogenous, fine, gray powder.
► The smaller the particle size, the better the hardening process. This is because, there is more surface area for the cement and water to react.
► The curing process of cement releases some heat, called the heat of hydration.
► The compressive strength of ordinary Portland cement ranges from 1800 psi to 3000 psi, depending on its type.
► Cement which contains slag is more chemical-resistant.
► The time taken by cement to cure is called the setting time. This is divided into the initial setting time and final setting time. The initial setting time is when the cement begins to harden. The final setting time is when it completely loses its plasticity, and can bear loads.
► The recommended initial setting time for Portland cement is a minimum of 45 minutes.
► The recommended final setting time for Portland cement is a maximum of 600 minutes.
► Concrete is a composite material in which the properties of the final product are different than that of its ingredients.
► It is stronger and more durable than either cement or mortar alone.
► By weight, 10 – 15 % of concrete is made up of cement.
► When it is poured in the mold, it is thin in consistency, because of a low water-to-cement ratio.
► It has the highest structural and compressive strength, because it contains coarse aggregates like rock chips.
► The compressive strength of concrete lies in the range of 3000 to 6000 psi, though concrete of strengths as high as 10,000 psi is used for certain applications.
► It is commonly reinforced with materials like steel to make it even stronger and protect it from settling soil.
► Adding calcium chloride to concrete will speed up the curing process, while sugar slows it down. These substances modify the hydration process of cement.
► Concrete requires exposure to water to cure well. This is why the surface of concrete is most likely to be brittle, because it loses water by evaporation.
► It is resistant to fire and has low maintenance.
► Its setting time depends on the temperature; it may be as high as 19 hours at 30ºF, while at 100ºF it hardens only after 1½ hours.
► Unlike mortar, concrete has no bonding properties and cannot be used for masonry work for sticking bricks.
► It gets stronger as it gets older, as the curing process of the cement in it continues for years.
► Mortar is stronger than cement alone, but has lesser strength than concrete.
► When mixed with water, it forms a sticky paste, which easily adheres to stones or bricks.
► It forms a homogenous paste on addition of water, unlike concrete which contains large aggregate.
► Mortar has a higher water-to-cement ratio, which makes it thicker on adding water. It also retains more water than concrete.
► It is intentionally designed to be weaker than concrete. This is because it is designed to bind bricks together in a wall. Walls shift frequently because of moving foundations. If the mortar would have been stronger than the bricks, then the shifting would damage the bricks, making it necessary to rebuild the entire wall.
► When a piece of mortar breaks out from the wall, it can be easily repointed (i.e., fresh mortar can be applied in the gap).
► Mortar is less durable than concrete and has to be replaced once every 25 – 30 years.
► Additives or plasticizers are commonly added to increase its flexibility.
► On solidification, mortar must form air spaces, unlike concrete which is solid. This is because, mortar contains more water, which freezes in cold weather. Ice occupies more space than liquid water, thus the forming ice crystals need some space to spread, or else they may damage the wall.
► Mortar prevents air or moisture from entering the structure, and forms a tight seal.
► Its compressive strength is between 900 to 2900 psi, depending on the type.
► Its setting time is from 24 hours to several years; the hardness increases with time.
- It is used as an ingredient of concrete and mortar. It works as a glue which holds the sand and aggregate together in concrete.
- Cement slurry is used to fill cracks in concrete structures.
- It is used to make lamp posts, railway sleepers, cement pipes, and telephone poles.
- Cement cannot be used by itself, like concrete.
- It is used in construction work, because of its capacity to bear heavy loads. It is used in support beams, concrete pilings, and supports.
- It can be used alone to construct a concrete wall, driveways, sidewalks, blocks, beams, and slabs.
- It is used in construction of buildings, runways, dams, and bridges, because of its durability.
- It is used for decorating fireplaces, porches, and pool decks.
- Concrete is one of the most-widely used construction materials.
- Because of its low strength, mortar cannot be used alone.
- It is used as an adhesive to bind masonry units such as bricks and stones together while constructing walls.
- It is used to fix tiles on floors. Before laying tiles, a layer of mortar can be applied on the floor.
- It is used to repair walls with gaps between the bricks. Mortar can be prepared and used to fill the gap, thus strengthening the wall.
Thus, while concrete and mortar are stronger, they cannot be produced without their main ingredient – cement. Cement, concrete, and mortar, all have their respective uses in construction work, and substituting one for the other can be dangerous for any structure.