Scientific journal
Modern high technologies
ISSN 1812-7320
"Перечень" ВАК
ИФ РИНЦ = 0,969

In the situation of diminishing natural silicon raw materials it is necessary to use for, example, the wastes from the pulp production, the thermal fly ash of heat - power station and amorphous microsilica.

The production technology of ceramics with pores by foam making is quite easy, though the production of quality material is possible only with the strict observance of numerous small details. It is especially important with the raw materials based on technological wastes.

The problems of production ceramics with pores from dispersed technological wastes for construction purposes could be classified as follows:

  • manufacturing of the rigid matrix convenient for making pores;
  • selection of the effective foaming agent;
  • control of water to solids relation;
  • control of influence of high humidity and reinforcement of the pores cage during the first stages of solidification;
  • selection of the optimum mode of thermal treatment.

Combination of high calcium concentration ash with amorphous silica compound (microsilica) case the production of rigid ceramic tile [further used in the process as matrix for making pores in construction materials.

The undertaken researches showed that the by-products and modified wastes from sulfate pulp production could be used as foaming agents. For example - the water solution of detergent Taiga" and emulsion of tall pitch.

High dispersive of the amorphous microsilica (S=250000 cm2/g), the wastes of crystal silicon and at lover level the high calcium concentration ach predefine the high water consumption of the compound. In addition, adding the foam to this system demand to use the compounds with high water consumption. Insufficient mobility of the mixture cause the destruction of the foam bubbles and the excessive humidity also changes the theological properties of the mixture ad prevents its structurization. The results of the researches showed that to get the material with the density of 400-800 kg/m3 on the base of the above mentioned wastes the relation water-to-solid of the mixtures should be 1,3-0,9.

This high water trapping considerably slow down the setting of the mixture and decrease the rigidity properties of the dried semi finished and final products.

Adding of Na2CO3 increase the rigidity of the construction materials, ashes and microsilica and also the porous materials. When adding 4-10% of mass of dried compounds the rigidity of the semi finished product during its pressing increases in 20-30% due to the reaction of hydration setting. Na2CO.3. acts also as diluter and when its concentration increases to 5-10% the water consumption decreases in one third (water-to-solids=0,68) maintaining the same consistency. During the firing the additive Na2C03 know for its flux properties intensify the collection of melt silicon, which make the monolith from hard melting particles. Due to the flux action the rigidity of the burnt material increases in 35-40%.

It should be noted that the beginning of the setting of this mixture begins in 10-20 minutes, though the stability of the foam based on detergent "Taiga" is 40-60 min, that means that the structurization of the system is taking place before the destruction of the foam.

To eliminate the distortion and high shrinking deformation the drying of the material should be done at the temperature not more than 60°C. To have the possibility of easy taking away of forms, the material should have some residual humidity, which is necessary for particles adhesion due to intermolecular interaction, when the water in very thin films has the adhesive effect.

The rigidity properties of the material also depend on the modes of thermal treatment. The researches showed that the increasing of the standby time at the maximum firing temperature (900°C) increase the rigidity of the material (up to 50%), accompanied by the increase of firing shrinking from 6-7 to 8-10%.

The mathematical model of the experiment aimed to evaluate the influence of throe major factors (content of Na2CO3, flow of foaming agent - detergent "Taiga" and temperature of firing) helped to define the optimum compound composition and the temperature of thermal treatment.

The compound having more balanced characteristics should be fired at 900°C and have 7% of foaming agent and 6% of soda: Compressive strength - 1,63 MPa, average density - 0,68 g/cm3, the construction quality factor - 22,1*10-4, thermal conductivity (according the empirical formula of V. P. Nickrassov) - 0,24.

The alternative version of additive instead of soda is wastes containing fluorine of Bratsk Aluminium Plant. The using of spent coal living gave a chance to get effective wall ceramics and foam ceramics with a minimum shrinkage.