Mechanical activation of binders by free-kick method
One of the most promising methods for optimizing the use of natural resources in the construction industry is the activation of binders. The increase in the useful properties of binders caused by activation allows you to reduce consumption and significantly increase the strength of products, reduce the time to set brand strength. With the help of activation, it is possible to fully use the potential energy of the material, reduce the cost of work.
Gypsum binders are activated by fine grinding the material and increasing its specific surface area, destroying weakened and structurally unstable particles, which leads to a significant improvement in the quality of newly formed surfaces. The activation technique has long proven itself in the treatment of low-grade and stale cements in order to restore and improve properties. The production of modern heat-efficient building materials, in particular autoclaved cellular concrete, is unthinkable without extensive use of grinding equipment.
It is known that in the process of fine grinding of bulk materials, only a part of the total supplied energy is consumed for the formation of a new surface, the rest of the energy is accumulated in the processed material in the form of stressed structural defects. This accumulated energy subsequently has a significant impact on the speed of various technological processes, as well as on the basic mechanical properties of the resulting materials.
However, after some time, the amount of accumulated energy decreases due to relaxation processes in the material, and a decrease in the initial activity of the material is observed. Moreover, the rate of relaxation processes depends both on the properties of the processed material itself and on its storage conditions. Depending on the temperature, humidity and some other conditions, there is a decrease in the activity of newly formed surfaces and, as a result, a decrease in the overall activity of the treated material. Thus, we can make a logical conclusion that in order to obtain the maximum values for improving the basic properties of materials based on activated components, it is necessary to organize the activation of materials in such a way that the time from fine grinding to direct use of activated components is minimal.
Directly during the activation of cement, the following studies were conducted. The maximum activity of cement after its processing on a shredder - disintegrator (free-impact grinding) was maintained for two hours. Then, a 5% decrease in the strength of the cement stone was observed (a decrease from the strength of the control sample formed immediately after the cement activation). When grinding quartz sand, the maximum activation effect was maintained for 12 hours. Thus, as mentioned above, the efficiency of using the method of fine grinding of materials directly depends on the degree of technical equipment of each specific enterprise and the expansion of the model range of material activation units in order to adapt them to the conditions of existing production facilities for the production of products and materials in the construction industry.
Taking into account that the activation of binders by fine grinding is the most cost — effective enterprise, the widespread use of grinding equipment in the production of building materials is an almost non-alternative way to increase the economic efficiency of construction. It is the activation of binders in general and the activation of cement in particular that opens up opportunities for qualitative improvement of the basic physical and mechanical parameters of concrete and products based on it. Cement activation measures that allow increasing the activity of cement, more fully using the mass of cement particles in the bonding of individual aggregate grains of various sizes into a single monolith, and increasing the strength of interpore walls in the production of foam concrete, aerated concrete, and polystyrene concrete should be used in the daily practice of modern construction materials production.