Cement hardening time and traditional work order
Cement is the most traditional astringent for producing various concretes. Its rational combination in a mixture with other fillers( gravel, crushed stone, sand), water and additives for various purposes is the basis of common artificial stone materials.
But the process of creating a concrete product is rather complicated and includes a whole sequence of works performed in stages, beginning with the selection and connection of components for the creation of the mixture, ending with the necessary care of the laid solutions after the beginning of their hardening.
The theoretically correctly prepared cement-based composition, after being poured into forms of formwork and seals, begins to harden, gradually increasing strength. Such an artificial stone immediately after drying does not have sufficient characteristics to continue construction on its basis: at first it easily breaks down from any load.
During the hardening of cement, the minerals of its grains are converted into extremely strong compounds, called hydrosilicate potassium. This transformation, starting avalanche, gradually decreases its speed and lasts for a long time, lasting for years at a time.
However, the time given above is sufficient to obtain the level of strength necessary to continue the construction. In the case of particularly responsible concreting, the period allowed for hardening the composition can be increased to three months or more.
Cement setting time - what influences this indicator?
In order for the setting process to begin and pass with increasing strength characteristics, certain conditions are necessary. For example, in the conditions of frost, when the water in the solution simply freezes, the seizure may not start at all, the magic transformation does not occur by hydration.
The aforementioned setting time for cement assumes quite certain conditions for external or internal works. Existing rules specify the temperature limits( about twenty degrees Celsius), normal pressure, average humidity, other factors( protection from direct solar heating).To further increase the strength at first, concrete requires certain care, periodic moistening, closing from direct sunlight.
This is achieved by the use of special films and moisturized fabrics, preventing rapid loss of moisture. It is perfectly permissible to use traditional coatings from sawdust, straw, with obligatory periodic moistening, especially in the first week after the mortar laying in the formwork.
The quality of the resulting stone directly depends on the activity factor of the binder itself, i.e.from its quality. The brand meeting the requirements of high quality, provides and the corresponding quality of the product. How much the cement stiffens depends on the correctness of its relationship with water.
As we have already explained, the monolith of the structure is ensured by the reliable bonding of the aggregate elements in the solution by the binder. In turn, this cohesion occurs as a result of its reaction with water, so the correct choice of the ratio of these two components is so important.
How can I influence how much cement dries?
The requirements discussed above, which ensure normal concreting, are not always respected in real construction. It is difficult to provide the necessary stability of weather conditions, ambient air temperature, etc. Therefore, a number of measures have been developed that make it possible to influence the process, i.e.on how long the cement dries.
For example, for work in low-temperature conditions, heated mortars are used. There are invented cunning methods of electrical heating, creating effects of thermos, special teplichki, heating with steam, etc. By the way, the hydration process of hardening itself is accompanied by the release of a sufficient amount of heat, which, for large volumes of work, often has a negative value.
For concreting on an accelerated schedule, substances that reduce setting time, both salt and salt-free, can be used. Such materials include sodium, calcium and potassium compounds( nitrites, nitrates, carbonates), for example, potash.
The opposite effect, retarding hardening, has additives used, for example, when delivering finished mixtures to objects, etc. As a rule, surfactants have properties of retardation of hydration. Their content in the formulations is determined depending on the ratio of water and binder component.