FAQs

Cement is a fine mineral powder manufactured with very precise processes. Mixed with water, this powder transforms into a paste that binds and hardens when submerged in water. Because the composition and fineness of the powder may vary, cement has different properties depending upon its makeup. Cement is also known as a binder it is the main component of concrete, a substance used in construction that sets and hardens and can bind other materials together

Portland cement is the most common type of cement that is used in general all over the world. This cement is made my heating limestone with other material. Portland cement is a basic ingredient of concrete, mortar and grout. It is most common use for the production of concrete. Concrete is formed when Portland cement creates a paste with water that binds with sand and rock to harden. As a construction material, concrete can be cast in almost any shape desired, and once hardened can become structural element. Without concrete any buildings or construction is not possible.

Portland cements are hydraulic cements these are the cements that set and harden by reacting chemically with water. Though all the Portland cements are quite similar. There are various types of Portland cement and are manufactured to meet the different physical and chemical requirements for specific purposes. The mentioned bellows are the different types and purposes of Portland cement.

• Type I - this one is known as common or general-purpose cement. Which is also known as ordinary Portland cement.
• Type II- this one give off less heat during hydration. This type is for general construction.
• Type III – this one has relatively high early strength. This is similar to type I but ground finer.
• Type IV- Portland cement is generally known for its low heat of hydration. This type of cement is generally used for very large concrete structures, such as damns, which have low surface to volume ratio.
• Type V- this type is used where sulfate resistance is important, it is used in concrete to be exposed to alkali soil and ground water sulfates which react with (C3A) causing disruptive expansion.

The advantages of using OPC are

• Ordinary Portland cement sets more quickly, and attains 85% of its maximum
• OPC is mostly used for large construction projects as it also sets and gain strength within 7 days.
• OPC is most prevalent because of the readily available raw materials where it is produced.
• OPC is also a Low – cost cement product that leads to OPC being widely used in the world to produce concrete. Which is the most popular material used for construction in the world being roads, buildings, and damns.
• OPC is also used for mortars and in making grouts.

To ensure the level of consistency between cement producing plants. Certain chemical and physical limits are placed on cements. These chemical limits are defined by a variety of standards and specifications. Different standards are used for classification of cement. The two major standards are the ASTM C150, which is primarily used in the USA and European standards EN 197. EN 197 cement types are CEM I, II, III, IV, V do not correspond to the similarly named cement types in ASTM c 150.

Strength of cement is definitely the most important, the grades mentioned in the cement bags as 53/43 OPC/PPC in fact represent the strength of the cement 53 grade OPC simply means that 28 days compressive strength of cement mortar cubes prepared out of that cement in a standard manner. Strength of cement is carried out on the cubes of hardened Cement – sand mortar not on a neat cement paste.

The methods to determine the physical properties of cement are:

• Determination of setting time of the cement
• Determination of the consistency of the cement
• Test for the compressive strength of cement.
• And test of cement’s fineness, soundness

Compressive strength –Using 50mm mortar cubes made by standard sand and cured in prescribed way tests compressive strength of cement. The cubes are tested under a compression-testing machine. The strength of cement varies with time.

Setting time - The initial setting time is the time that passed from the instance of adding water until the pastes ceases to behave as fluid or plastic. Whereas final setting time is referred to the time required for the cement paste to reach the state of hardness to sustain load. Using Vicat apparatus or Gillmore needle tests setting time of the cement.

Normal consistency of cement – consistency of a cement paste basically refers to the ability to flow. The water content in the cement that is at standard point maintaining the wetness is the normal consistency of cement.

The nature of the cement can be the reason for slow or fast setting of concrete or mortar but it can also be due to other irrelevant factors to cement. During hot weather the setting is faster whereas, in winter setting is delayed, the types of chemicals, clays, salts etc. if inadvertently get mixed with the sand, aggregate or water then also it can result to delay of the setting of concrete.

Setting time of cement is controlled by the Gypsum (CaSO4.2H20) that is actually added to clinker prior to finish grinding. Gypsum controls the C3A compound when water is added to cement.

It is difficult to distinguish the brand of the cement by its color. However, there can be a possibility to use analysis to know the brand the owner.

We cannot gauge the quality of cement by just looking at its color. The color of the cement is governed by its C4AF content the more C4AfF the darker the color of the cement will be. The quality of cement can only be gauged after analyzing the complete physical and chemical characteristic of cement.

Uses of high quality raw materials and the proper use of manufacturing process or high quality process can lead to producing high quality cement.

The factors that affect the quality during storage are temperature and humidity conditions, storage time, composition of clinker and gypsum, fineness of cement. Since cement is a moisture sensitive material, keeping it dry will retain it quality.

The improper handling and storage of bags can cause hardening in bags.

It is very important to know how to store cement to prevent cement from damaging. Here are few things that are to be kept in mind while storing cement.

• Cement should always be stored in a dry place, as it should be protected from rain. Or a building or go down only after ensuring that the buildings are weatherproof.
• Cement absorbs moisture from the air; therefore doors and windows should be kept closed to eliminate damp air or draughts.
• We must never store cement with other products such as fertilizer, gypsum based products or even foodstuffs, as it can have a disastrous results on the performance of cement in mortars, plasters or concrete
• It should be stored in a big empty room or a place that can keep the cement bags safe from being snagged or damaged.