Hydration, cement mix colloidation and false setting? Let's figure it out!

Cement is a mineral substance with an astringent consistency, which is produced artificially and turns, after its interaction with water, into a plastic mass that hardens after drying. This building material differs from other binding substances in its ability to set, gaining strength, even at high humidity. Cement is used mainly for the preparation of concrete mixture, as well as various solutions. To learn how to use this unique building material correctly, it is necessary to study all its properties and characteristics and understand what processes occur in concrete or cement mortars (plaster, adhesive and other appointments).

Reference to GOST 30515-2013 Cements:
GOST 30515-2013 Cements. General specifications

Hydration
As you know, cement is a hydraulic binder. In other words, to obtain a solid stone-like body, the powder used should be filled with water. By adding the required amount of water, you start an irreversible process that can be controlled if desired.
What happens during this irreversible process?

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Let's clarify in simple words. A chemical reaction begins: water molecules combine with mineral molecules that are part of the cement. This leads to the dissolution of the powder and the formation of a plastic mass. The phenomenon in which water combines with the material dissolved in it is called hydration.

In the course of hydration, a gradual saturation of the solution with reaction products occurs, which are responsible for the strength characteristics of the future product.

At a certain point, the dissolution process ends, and the cement mass loses its mobility and grabs, turning into a jelly-like mass. Grasping occurs shortly after mixing the solution - in the very first hours.

The start time of this process, called colloidation, as well as its duration depend:

on the amount of water used;
temperature regime;
the composition of the cement;
fineness of grinding of cement powder;

The finer the grind, the faster the setting will be. To delay the setting process and stretch it, the moving mass should be constantly mixed. But it is impossible to maintain the plasticity of the solution for an infinitely long time, the viscous mass at a certain moment begins to lose its useful properties.

It is recommended to study the cement in advance, which will help determine the actual setting time of this material and, if necessary, adjust them using special additives. Sometimes the material sets very quickly, almost immediately after interacting with water, and generates a lot of heat. This phenomenon is called false grasp! And in order to prevent it, the solution can be "Revive" by stirring.

"False grasp"- negative property of cement, such material is usually rejected.

When the solution loses its mobility, the particles of cement dissolved in it begin to crystallize, increase and intertwine, coalescing into a cement stone. This process proceeds at different rates - at first, the mass quickly becomes more and more durable, and then its crystallization slows down somewhat.

Final hardening can last for years, but the design strength grade of the resulting products achieved in twenty-eight days, demoulding at favorable humidity and temperature is possible after three to five days.