SU40895A1 - Method for making hydraulic cement - Google Patents

Description

It is well known that the hydraulic properties of cement depend to a large extent on the so-called hydraulic module, i.e., on the ratio between the number of basic and acidic base parts. The rate of hardening of the cement increases as the hydraulic module increases, or, practically speaking, as the ratio between the amount of calcium oxide and the amount of acidic components increases. However, the possibility of increasing the lime content is limited and depends largely on the degree of grinding of raw materials. The finer the ground raw materials, the more calcium oxide can be used in the mixture of materials intended for sintering, without fear that the lime contained in the mixture will remain in the clinker in an unrelated form and will cause an unacceptable appearance that is expressed in heaving cement.

Meanwhile, the grinding of raw materials. down to the finest subtlety is very expensive.

The purpose of the present invention is to obtain quickly hardened, i.e., high-modulus cement, by using raw materials ground only to the extent that is normally used to prepare normal Portland cement, and the resulting cement does not have a tendency to swell. .

According to the invention, the desired result is achieved by using a mixture of raw materials in which the lime content exceeds the amount of lime bound by other parts of the mixture during calcination, so that some free lime remains in the clinker and during or after the grinding of the clinker said free lime is hydrated in a particular way, and the cement itself does not hydrate. It turned out that similar hydration of the free lime contained in the clinker can be made by treating the cement mass, during or after grinding, with steam or finely sprayed water at a temperature of approximately 80 to 210, mostly at temperatures above 100 °, as experience has shown that in the range from 100 to 210 lime hydration goes faster than at 100 and below. If the hydration is carried out at higher temperatures, which lie within the above limits, then the hydration of the cement itself is practically excluded, whereas at lower temperatures the latter occurs in considerable sizes.

so, the pursued goal is over or. less fails.

For example, if, with very fine grinding of raw materials containing 66% lime, such clinker is obtained, which, after grinding, produces non-perturbed, i.e., having constant volume of cement, then if the same percentage of lime is used in a mixture of raw materials, As long as it is usually practiced in the manufacture of normal Portland cement, clinker is obtained, in which the amount of bound lime is too small to give quick-setting cement. In addition, the resulting grinding of clinker (cement) would have a tendency to swell. Even if cement were able to puff away after hardening, subjecting it to a process according to the invention that results in free lime hydrating and the cement itself not hydrating, the goal of obtaining quick-hardening cement is certainly not achieved, since the hydraulic module of this cement lie below the value of 2.20 required for quick setting.

In order to get quick-setting non-learning cement in this case, without resorting to too fine grinding of raw materials, it is necessary to increase the lime content of these materials to 68%. When the raw mix is burned in this case, free lime also remains in the clinker, but still the amount of bound lime is greater than with 66% lime in raw materials, and this increased amount of bound lime is enough to make the finished cement free to hydrate. lime, according to the method proposed here, had a hydraulic module of 2.2 and higher and, thus, the cement would have a quick setting.

Although the speed of hardening of cement depends not only on the hydraulic module, but also largely on the so-called silicate module, i.e., on the ratio: the amount of silica in the mixture to the acid to the amount of alumina and iron oxide, nevertheless , in connection with the invention, there is no need to consider these additional factors, since the invention is directed solely to the effect of lime, and the purpose of the invention is to increase the rate of hardening by increasing the lime content and eliminating harmful consequences associated with such an increase.

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The subject of the patent.

A method of manufacturing hydraulic cement, characterized in that in order to achieve hydration of free lime without hydration of the whole cement, the grinding of clinker is carried out by admitting steam into the grinding apparatus, preheated to a temperature ranging from 80 to 210.