Old Portland cement 52.5 is the highest grade commercial Portland cement widely available on the market. With a minimum compressive strength of 52.5 MPa (or 525 kg/cm2) attained on the 28th day after pouring, OPC 52.5 is suitable for large load bearing structures such as high rise buildings, bridges, and other such projects.

OPC Grades

OPC grades are very straightforward and easy to follow. The numerical rating following the prefix ‘OPC’ is the minimum compressive strength which cement must attain on the 28th day after pouring in order to be classified as being a particular grade. It is worth noting that the 52.5 MPa rating is simply a minimum requirement, and most OPC 52.5 MPa cements exceed that strength.

The two most commonly available Ordinary Portland cement grades sold today are OPC 42.5, and OPC 52.5. There is no difference in chemical composition between the two cement grades, however OPC 52.5 is more finely ground than OPC 42.5, which results in different properties when mixed and poured.

Making OPC 52.5

OPC 52.5 is made according to normal Portland cement standards, and is composed of a minimum of 66% calcium silicates, along with a smaller amount of iron and aluminum The raw material from which OPC is sources usually includes limestone and clay (over 85%), as well as silica sand, iron ore, and other sources of the primary components of Portland Cement. Raw materials normally vary depending on the region where rock is mined, as some areas are rich in the natural resources which are needed for Portland cement production, and others are not, in which case raw materials must be brought in to supplement local supply.

The production of Portland cement begins with the preparation of the raw mix. Because it is so important that each component be present in precise quantities, it is quite common for individual silos containing a single raw material to be positioned over a conveyor belt and to be computer controlled to release the right amount of raw material onto the belt to be carried into the raw mill, where the raw materials are ground together. Cement making is a very precise art, requiring workers to have skill, expertise and dedication to quality control. Even small variances in composition can ruin an entire batch of Portland cement.

The ground up raw materials are referred to as ‘raw mix’, and once created, this raw mix is taken from the raw mill to the blender, where it is thoroughly mixed to ensure that it is a homogeneous batch with no irregularities in it, and chemically analyzed to ensure that the correct portions of raw material are present. Raw mix may either be blended dry, or it may sometimes have water added to it and be blended as a slurry.

Once the blend has been correctly portioned and analyzed it is sent through to the kiln, where it is fired at temperatures exceeding 1400 degrees Celsius. The firing process causes the aluminum and the iron to melt into their liquid states, in which they act as fluxing agents, lowering the temperature at which calcium and silica form calcium silicates which are the main component of Portland cement.

The end product of the firing process is a plethora of small nodules called ‘clinker’. Once produced, clinker can be cooled and taken to storage, or it may be quickly cooled and sent directly through to the final stage of Portland cement production, grinding, where the nodules are put into a revolving grinding chamber and ground to a very fine powder. An additive known as gypsum is also added at this stage in order to control the speed at which the cement will set once poured.

When the grinding process is finished, the result is high quality OPC 52.5, ready to be bagged and sold as an additive in concretes, mortars, and other construction materials.

OPC 52.5 Exporters

We export all types of cement in bulk quantities. Please contact us through this form below and let us know your specific requirements. We will get back to you with the price quotation within the same day

Cement 52.5

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