Effect of modifiers and mineral additives from industrial waste on the quality of aerated concrete products

The given article is devoted to research of influence of polymer modifiers and mineral additives on quality of composite aerated concrete products. When selecting the composition of composite aerated concrete local raw materials and components were used: portland cement, sand, aluminum powder, polyvinyl acetate, fly ash, post-alcoholic bard and whey of milk. Preliminary polyvinyl acetate was combined with binder mixing water at a temperature above 55ºC to obtain a readily soluble polymer emulsion. Dispersion was carried out with a rotary-pulsation apparatus at a pressure of 0.5-1.0 MPa and a rotor speed of ~1200 rpm. In the same apparatus the complex modifier was produced. The offered technology of production of a complex modifier seems to be the most effective for composite aerated concrete. It made it possible to reduce water absorption and capillary suction of composite aerated concrete by an average of 25% and 45%, respectively. Moreover, different combinations of fly ash, polymer and modifier made it possible to achieve optimal values of thermal conductivity, compressive strength and frost resistance of composite aerated concrete.

Rotary-pulsation apparatus for preparation of liquid grain feed

Existing feed devices use methods of grinding grain and other components of the feed mixture in hammer crushers, which requires significant costs of mechanical (electrical) energy. Therefore, it is necessary to develop devices with a high degree of impact on the treated environment, which increases productivity and reduces energy consumption in technological processes. Such devices include rotor-pulsation devices, the principle of operation of which is based on the method of discrete-pulse energy input. The basis of this method is a multifactorial effect on the treated liquid homogeneous or heterogeneous medium, which consists of pressure pulsations, changes in fluid flow rate, intense cavitation, developed turbulence, hard cumulative effects, as well as high shear forces. The purpose of the study is to conduct a comprehensive analysis of kinematic and dynamic characteristics and establish the features of discrete-pulse energy input in the dispersion of grain mixtures in a rotary pulsation apparatus and develop on this basis energy-saving technology and equipment for liquid grain feed. A numerical and experimental study of heat and mass transfer processes in rotary pulsation apparatus for the preparation of liquid grain feed has been carried out. The basic hydraulic and thermal characteristics of such devices are received and geometrical characteristics of such device are defined. Experimental samples of the device for rectangular round shape of openings in the rotor-stator system are developed and made. Experimental studies of such characteristics as particle size distribution of grain feed mixture, power consumption in feed production and temperature change of water-grain mixture during its processing have been carried out.

MECHANOCHEMICAL METHOD OF PROCESSING SILICA-CONTAINING PLANT MATTER

The possibility of complex processing of silica-containing plant biomass with the selection of a line of target products is investigated. The method includes the mechanochemical treatment of biomass in a solution of sodium hydroxide in a rotary pulsation apparatus at a temperature of self-heating not lower than 80 °C. The resulting suspension is separated on a solid residue and an extract. The solid residue is washed and dried to obtain pulp powder. The bio-filled silica gel with an SiO2 content of 49.4 wt.% to 62.6 wt.% is isolated from the extract after separation of the solid residue. By ashing the silicon-containing product at a temperature of 600 °C, amorphous silica is obtained. The content of SiO2 (as the target component) in the ash is 85.5–92.0%. The SiO2 diffraction pattern is characterized by the presence of a diffuse halo with a maximum at 2q=22.75 ° and the absence of diffraction peaks. Preliminary acid leaching can increase the purity of the resulting silica to 99.0%. The specific surface area of the obtained silica was determined by the BET method for nitrogen sorption at 260 m2/g. The effect of the concentration of the extractant on the yield of alkali-soluble substances and the degree of leaching of silicon was studied. It was shown that even at a 1% concentration of the extractant (NaOH), almost complete leaching of silicon from the plant matrix occurs. Depending on the increase in the concentration of NaOH, the degree of delignification of the biomass increases to 13–18–22%, respectively, with an increase in the concentration of NaOH 1–5–10%. Powdered cellulose was obtained with a content (%): silicon – 1.12, lignin – 34.8, alpha cellulose – 86.0, with a yield of 33.0% and a particle distribution of 80–300 μm. The amount of biomass loss is 17.6 wt.%.

CONCRETE COMPOSITION PROPERTIES MODIFIED BY POLYMER EMULSION

The paper deals with the quality of gas concrete by using a number of process technologies that can significantly improve the potential of the added components. The proposed technology for composite gas concrete production improves its physical-and-mechanical properties due to the use of a rotary-pulsation apparatus, which creates high-frequency vibrations accompanied by cavitation and produced a high-quality polymer emulsion and the aluminum powder. Due to high-quality saponification, the gasifier evenly distributes in the concrete paste structure and reacts with the cement binder, thereby creating a uniform pore space. And the polymer emulsion envelopes pores and improves the material hydrophobicity and strength.

Study of wheat straw delignification in a rotary-pulsation apparatus

This paper presents the results of studies of isolation lignin and hemicelluloses efficiency during the pre-treatment of wheat straw for hydrolysis in a rotary-pulsation apparatus. The pre-treatment of lignocellulosic raw materials for hydrolysis is a necessary step in the second-generation bioethanol production technology. The lignocellulose complex is destroyed during this process, and this allows hydrolytic enzymes access to the surface of cellulose fibers. The pre-treatment is the most energy-consuming stage in bioethanol production technology, since it usually occurs at high temperature and pressure for a significant time. One of the ways to improve the efficiency of this process is the use of energy-efficient equipment that allows intensifying heat and mass transfer. An example of such equipment is a rotary-pulsation apparatus, which are effective devices in stirring, homogenization, dispersion technologies, etc. The treatment of wheat straw in a rotary-pulsation apparatus was carried out under atmospheric pressure without external heat supply at solid/water ratios of 1:10 and 1:5 in the presence of alkali. It was determined that the treatment of the water dispersion of straw at ratio of 1:10 due to the energy dissipation during 70 minutes leads to the release of 42 % of lignin and 25.76 % of easily hydrolyzed polysaccharides. Changing the solid / water ratio from 1:10 to 1:5 leads to an increase in the yield of lignin and easily hydrolyzed polysaccharides to 58 and 33.38 %, respectively.

The Increase of Hydration Activity of Portland Cement by Additives of Crystalline Hydrates

The article presents the results of a study of the effect of synthesized microdisperse additives of crystalline hydrates based on calcium sulfoaluminates on the properties of cement stone. The effectiveness of the use of a rotary pulsation apparatus (RPA) to obtain microdispersed additives is identified. The possibility of accelerating the hardening of cement stone by entering microdispersed additives into its composition is shown. It has been established that in the presence of microdispersed additives of crystalline hydrates in the cement stone, the phase composition of hydrate tumors changes, the amount of calcium hydrosilicates and ettringite increases, the porosity decreases and the strength of the cement stone increases. This provision is confirmed by the increase in the degree of cement hydration, the amount of bound water in all periods of hardening of the stone. It is proposed to use microdisperse additives, which play the role of primers for the crystallization of ettringite and calcium hydrosilicates, to increase the strength of cement stone in the early stages of hardening.