Papers by Keyword: Alkali Resistance

Abstract: The paper presents studies on the properties of various types of micro-reinforcing fibers to assess their role and effectiveness in the structure formation of the cellular composite. Based on the data on the weight loss after exposure in a model medium of cement, analysis of the alkali resistance of fibers of five different types – basalt fiber, heat-treated basalt fiber, polymer fiber and glass fibers from two different manufacturers – was carried out. It is shown that the fibers have a sufficiently high durability in the medium of hardening cement, which is expressed by a relatively insignificant weight loss of the original fiber after exposure in a model medium for 28 days in ambient conditions. The weight loss for some fibers sharply increases when hardening conditions are changed to hydrothermal ones. The images of fibers exposed in a model medium of cement, obtained using scanning microscopy, were also analyzed, and the character of distribution of acidic and basic adsorption sites on the surface of fibers depending on the type was assessed. Based on the analysis of the obtained data, we can talk about a high number of active sites on the surface of basalt and glass fibers, which ensures the formation of crystalline new formations on them and makes it possible to predict their high adhesion to the cement matrix.

Abstract: The glass micro balls based on glass domestic waste for road construction were obtained. Glass micro balls will reduce the contamination of road marking and increase its light-reflective ability at night. Colorless and colored container glass, as well as lead crystal, was chosen as the starting material for producing glass micro balls. An electric arc plasmotron UPU-8M was used to produce glass micro balls. Pre-crushed fractionated glass together with plasma-forming gas – argon was fed to the powder feeder and from the feeder to the plasma burner. Under the influence of high plasma temperatures, about 9000-12000K, the particles were melted, followed by cooling in the outgoing flow of plasma-forming gases. Due to high-temperature plasma exposure, partial evaporation of alkaline oxides and lead oxide occurred. Glass micro balls were enriched with the oxides of silicon, aluminum and calcium. This helped to increase the acid and alkali resistance of glass micro balls. The micro hardness, density, and refractive index of glass micro balls were studied. It is shown that glass micro balls have an ideal spherical shape and are x-ray amorphous. Glass micro balls are recommended for use in road construction as a reflective element of road marking.

Abstract: Straw fibers reinforced geopolymer, a new type of metakaolin-based geopolymer, was synthesized in a specific formulation with rice straw fibers added. The straw-geopolymers were soaked in sulfuric acid solution at pH of 1.0, 3.0 and 5.0, respectively, and sodium hydroxide solution at pH of 9.0, 11.0 and 13.0, respectively. Compressive strengths and microstructural changes were studied. The results showed that after being immersed in acid solution at a pH of 1.0 or alkali solution at a pH of 13.0 for 28 days, the compressive strengths of the specimens decreased from 50.28 MPa to 28.90 MPa and 40.00 MPa, respectively. The best performance was observed when the specimens were soaked in sodium hydroxide solution at a pH of 9.0. Scaning electron microscope (SEM) analyses indicated that the lamellar structure of the straw-geopolymer was consistent with pure geopolymer. Cracks which led to a loss of strength were found in the specimens soaked in acid solution at pH of 1.0 and 3.0.

Abstract: The paper is devoted to the study of composite reinforcement made of glass fiber and basalt fiber, in particular their operational properties under the aggressive alkaline lightweight aggregate concrete environment. Their thermal resistance being sufficiently less than that of the regular steel composites they may be used in three-layered building envelopes to provide enhanced thermal properties. However there is lack of data and experimental results on the topic. Previous research indicated high alkali resistance of basalt fiber reinforcement, but there is a need in further studies. For the objective of the composite reinforcement that is used as flexible connectors for layer wall panels, a series of experimental studies. Research data have shown satisfactory performance study of flexible links.

Abstract: Using alumina-rich MgAl₂O₄ spinel AR78 and 97 fused magnesite as raw materials, brine as the binder, magnesia alumina spinel bricks close to theoretical composition and spinel bricks with zirconia have been prepared. Then the influences of zirconia on the properties of MgAl₂O₄ spinel bricks are researched. The results show that: (1) After the addition of zirconia, the direct bonding structure formed between spinel and zirconia can strengthen matrix structure and promote sintering, so the structural properties, the alkali resistance performance and the creep property of MgAl₂O₄ spinel bricks are all improved. (2) The optimal addition of zirconia is 6%, with which the spinel bricks have well alkali resistance performance and creep property of which the final creep rate is -1.46% after creep experiment for 50h.

Abstract: The soybean/casein/polyvinyl alcohol blend fiber was treated in sodium carbonate solutions to evaluate its alkali resistance which was very important for wet processing. The weight loss and whiteness of the treated fibers were examined. UV spectra of the alkaline treatment solutions were analyzed. The study showed that the fiber exhibited poor alkali resistance. Treating temperature, time and alkali concentration affected the weight loss of the treated fibers. A high weight loss was found even at low alkali concentration. The weight loss was primarily due to the hydrolysis of casein.

Abstract: As a new textile material, silk/PLA mixture combines the outstanding characteristics of silk and PLA fibers, but this mixture is subjected to some problems owing to the poor alkali resistance of PLA fiber during the pretreatment and reactive dyeing processes. In the present work, the alkali resistance of silk/PLA mixture was tested with three alkalis, namely sodium hydroxide, sodium carbonate and sodium bicarbonate. It was found that silk component was less influenced by sodium carbonate and sodium bicarbonate, whereas PLA component was more or less influenced by three alkalis. Silk/PLA mixture showed low weight loss after sodium carbonate and sodium bicarbonate treatment, but had very high weight loss after sodium hydroxide treatment. 10 g/L sodium carbonate and 3 g/L sodium hydroxide resulted in the obvious changes in the morphological structure of PLA. After the alkaline treatment, the IR spectra of PLA treated with 3 g/L alkali displayed great variations, and the intensity of the peak at 3429.3 cm^-1 increased with the strength of alkalis, showing that the partially hydrolysis of PLA occurred.

Abstract: The aim of this work is to assess the feasibility of using polymer mortars reinforced with untreated natural fibres instead of artificial ones, for applications requiring highly alkali resistant materials, such as tanks and drainage systems for wastewater treatment plants. For this purpose, several formulations of polyester polymer mortars reinforced with different contents of jute and piassava natural fibres were investigated. Flexural and compressive behaviour, before and after exposure to a strong alkaline solution was analysed and quantified. Test results highlighted the high potential of these materials as basis construction material for precast applications requiring specific resistance under alkaline environments.