Alumina cement: scope of use
This composition is used in cases where it is necessary to accelerate cementing operations. So, it is used by with fast erection of structures, for reinforced concrete bridge structures, in underground construction( including mines and metro), for industrial buildings, for cracks in the cellars, in all kinds of emergency cases, for lining all kinds of furnaces( thermal,roasting) and in many other situations.
Especially recommended is the alumina composition for the construction of reinforced concrete structures for special purposes in factories, that is, where finished products are manufactured. Their decking can be carried out within 12-16 hours( due to the rapid drying of the mixture).However, it is undesirable to use this material to create structures with a width of more than 1 meter. It is justified by the fact that temperatures in the interior of the massif are higher than 70 ° C, and hardening proceeds abnormally. As a result, the strength can be much lower.
Alumina cement: properties and technical characteristics of
This material is manufactured in accordance with GOST 969-91, according to which the amount of alumina in cement should be at least 35%.This mixture is divided into the following brands: 40, 50 and 60. Each of them has its own physical and mechanical characteristics. The ultimate compressive strength for a day is 22.5-32.4 MPa, for three days from 40 to 60 MPa. The setting process starts after 30 minutes, and ends after 12 hours. Bulk density in dry form is 850-1100 kg / m3.
If we talk about the properties of this material, we can distinguish fire, heat resistance, durability, strength, resistance to various aggressive media( gases and liquids).A particular advantage is the possibility of solidification of cement under wet conditions. And if you add this compound to the concrete, it acquires frost resistance and water resistance.
Note! The best conditions for hardening high-alumina cement( not to be confused with t heating the mass) is the average temperature of + 15-20 ° C.Also, the temperature can be above 30 ° C, but the strength of the material decreases( at least 3 times).
Terms of application of alumina cement
We will not talk about the technology of applying the compound, since it directly depends on which construction sector it is used in. Just describe in what conditions it is better to apply. The principle of manufacturing heat-resistant cement is completely different from mixing conventional Portland cement, the only difference is that it is not worthwhile to mix it in the concrete mixer( remember that the mass quickly solidifies).During hardening it is necessary to provide a wet mode( for example, protection from the sun).
During the preparation of the mixture, the conditions for heating the mass are created. If this is not done, then the concrete during the day, pour cold water. Watering is carried out during the heating start. Well, or no later than 8 hours after application.
In the case when concreting is done in winter at a temperature of -10 ° C, then any heating procedures may not be made. It is only necessary to avoid one moment - freezing in the first 1-2 days. In severe frosts, it must also be taken into account that the ability of the mixture to thicken significantly increases.