Difference Between Non-Hydraulic Cement & Hydraulic Cement

When it comes to the construction of homes, buildings, sidewalks, dams, bridges, etc., cement is an industry staple. Its unique and versatile qualities are well-acknowledged and make for its widespread usage. Despite such high demand for cement, many people are unaware of its basic types. Typically, cement is classified into two varieties based on its hardening and setting mechanism. These are- 

  • Hydraulic Cement
  • Non-hydraulic Cement

Non-Hydraulic Cement

As the name indicates, the non-hydraulic cement does not require water to harden. It will not set when wet conditions exist. Instead, all it needs are dry conditions and the presence of carbon dioxide (CO₂) to set and cure.

Non-hydraulic cement was probably the first known cement to humanity. However, due to its very restricting properties, it was essential to complete the builds quickly before inclement weather conditions hit. 

Hydraulic Cement

Hydraulic cement is an inorganic mineral material that reacts with water under ambient conditions forming a hardened and water-resistant product. The cement hardens by hydration in the presence of water. 

Hydraulic cement was first used in the middle ages by the Romans. At that time, “hydraulic cement” was made by combining volcanic ashes and lime. In the 18th century, James Parker patented the Roman cement, but subsequently, it was replaced by Portland cement sometime during the 1850s.

Difference Between Non-Hydraulic Cement & Hydraulic Cement

Now that you know what non-hydraulic and hydraulic cement are, let us look at how they differ.

Raw Materials

  • Non-Hydraulic Cement – The raw materials that make non-hydraulic cement are Lime, gypsum plasters, and oxychlorides.
  • Hydraulic Cement – the raw materials that help produce hydraulic cement are limestone, clay, and gypsum.

The Hardening Process

  • Non-Hydraulic Cement – Non-hydraulic cement hardens when a reaction occurs due to carbonation with carbon dioxide present in the air.
  • Hydraulic Cement – Hydraulic cement hardens when a chemical reaction occurs between the anhydrous cement powder and water. The resultant hydrates do not dissolve in water. Therefore, this cement retains its strength and hardness even when used underwater.

Strength Gain

  • Non-Hydraulic Cement – Hardening and strengthening go hand in hand as the cement gains strength as it hardens. Non-hydraulic cement usually takes a long time to harden compared to hydraulic cement. This tends to cause delays in the completion of construction projects, which is especially harmful when running on tight timelines.
  • Hydraulic Cement – Hydraulic cement begins to harden almost instantly, and sometimes the process can be completed within just a few minutes, as is the case when applied to small areas. In the case of large portions or more extensive projects, the strength-gaining process continues for a few days.

Existence Of Dry Conditions

  • Non-Hydraulic Cement – Non-hydraulic cement will not harden and gain strength until and unless the core requirement of the dry condition is met. Wet conditions do not allow this type of cement to be set.
  • Hydraulic Cement – Hydraulic cement can be set even when dry conditions are not met. It can harden while in contact with water and make for a strong build. Generally, project managers prefer using hydraulic cement because any major construction can take a few months to a year or more to complete. It means there’s no guarantee that dry conditions will persist.

Uses

  • Non-Hydraulic Cement – Non-Hydraulic cement is used for making bricks and mortar. Sometimes it is also used in stonework. Basically, you will find the use of non-hydraulic cement only indoors as that is the only place where you can ensure dry conditions necessary for its curing.
  • Hydraulic Cement – Hydraulic cement, due to its less restrictive nature in curing, is used for building dams, swimming pools, drainage systems, buildings, bridges, and so on. In fact, it is used in almost all types of civil engineering projects.

Examples

  • Non-Hydraulic Cement – An example of non-hydraulic cement is slaked lime or non-hydraulic lime putty.
  • Hydraulic Cement – A few examples of hydraulic cement are Portland cement, blended cement, blast furnace slag cement, etc.

Which Is Better Non-Hydraulic Cement Or Hydraulic Cement

Now we come to the most important question of the day – “Which is better: non-hydraulic cement or hydraulic cement?” To give a fair verdict, it is necessary to recap the qualities of both.

Although non-hydraulic cement is the first invented type of cement, its restrictive nature in requiring fixed dry conditions to cure makes it highly inconvenient to use. It does not harden as long as it is in contact with water. To dry and strengthen, it demands dry conditions. This puts a damper on things as it is not suitable for open construction sites, which are always at the mercy of nature. Due to the harsh fact that it needs controlled conditions, the use of non-hydraulic cement is very restricted.

The limitations of non-hydraulic cement led to the development of hydraulic cement. Due to its fast-drying time under every possible condition, it is now the first choice of all project managers. Hydraulic cement reacts with water and forms stable hydrates of calcium silicate, which results in its quick hardening when poured. Since most constructions are open sites, using hydraulic cement ensures there will be no unnecessary delay in completing the build.

The Verdict

Hydraulic cement cures quickly in dry and wet conditions alike, so it is a better option than non-hydraulic cement, which demands only dry weather. The hydraulic cement was developed for speed and convenience, delivering outstandingly on both. 

The Conclusion

While non-hydraulic and hydraulic cement types have their logical and clear applications, it is still easy to garner why hydraulic cement wins hands down. Understanding and acknowledging the limitations of the cement and the expectations for your project, you make the right decision by choosing the cement that best suits your project’s construction requirements. It is only fair to point out that more and more builders place their faith and trust in hydraulic cement, due to which non-hydraulic cement is slowly and steadily becoming obsolete and redundant. Nevertheless, how you want to proceed and which cement you want to work with (whether you want to use one or both) is a choice you must make for yourself. When you do that, simply consider the requirements of the structure you are planning to build, and you shall never go wrong.