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The PROMPT natural cement is the only one in the world to be industrially manufactured using the same process for over 180 years. Among the various manufacturing stages, let's take a look behind the scenes of our grinding process.


Discover our grinding method

A distinct name

The PROMPT natural cement is a clayey limestone directly extracted from the stone, fired at moderate temperatures (between 500°C and 1,200°C). After leaving the kiln, the stones are called "logs" and classified into three categories: undercooked, properly cooked, and overcooked, depending on their level of firing. A quality natural cement is distinguished by a well-proportioned mixture of these different logs. After firing, similar to natural hydraulic limes (NHL), the stone, which contains very little quicklime, does not undergo slaking, unlike these hydraulic limes. That is why its designation is natural cement and not natural hydraulic lime. Moreover, unlike ordinary cement, which involves the processes of firing, grinding, and cooling,  PROMPT natural cement is only fired and ground.

Crushed stones with a very high fineness. The fired stone is then crushed and finely ground in a rotary ball mill. The fired stones are ground to a very high fineness, about twice as fine as conventional cement. A final fineness much greater than that of ordinary cement. The next step is to regulate the quality variations through homogenization, which occurs by passing through a battery of silos. Each silo is then filled one by one. Subsequently, homogenization is achieved by withdrawing from all silos simultaneously to ensure a blend of all productions. It should be noted that the fineness of PROMPT natural cement makes it an easily formable material.

From the deposit to the finished product, no additives are used, which is what makes PROMPT natural cement unique. Derived from a unique deposit in Europe, PROMPT natural cement is an exclusivity of the Vicat Group. It is manufactured in the Chartreuse massif at our La Pérelle cement plant, established in 1875 by Joseph Vicat. To learn more, discover the backstages of our deposit and the history of our product (links). Natural cement PROMPT possesses exemplary properties. It is a durable, aesthetically pleasing material that offers good compatibility with lime and ancient substrates. To learn more about the manufacturing process, explore the history of our material and its firing process.


In the hearth of Chartreuse



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