Papers by Keyword: Aluminum Sulfate

Abstract: In this paper, the effects of various components in alkali-free accelerator on the setting of cement paste were studied, and the morphology of the hydrates during hydration was investigated with SEM. The experimental results show that the aluminum sulfate, diethanolamine and hydrofluoric acid can effectively shorten the setting time of cement paste, while excessive dosage has minimal impacts on the setting time. The diethanolamine and hydrofluoric acid can not only shorten the setting time but also can improve the stability of the accelerator. It was evidenced by the SEM that the aluminum sulfate accelerates cement coagulation by quickly forming a large amount of ettringite in the cement paste. The results in this study suggest that the shortest setting can be achieved when the dosage of aluminum sulfate, diethanolamine and hydrofluoric acid in a liquid alkali-free accelerator is 57 %, 5 % and 5.7 % , respectively.

Abstract: A highly porous structure of a gypsum product creation is possible due to the porisation of gypsum mass, using new types of complex gas-forming components. At the same time, it is necessary to determine the technological conditions for the optimal formation of porous gypsum products structure and methods for increasing their strength. The article proposed to use dispersed calcium carbonate and aluminum sulphate, which interaction is the reaction with the release of СО₂ for the porisation of the gypsum cast mixture. Micro-reinforcing additives, such as polymeric, basalt and glass fibers were introduced into gypsum composition together with building gypsum and finely ground calcium carbonate to improve the physico-mechanical properties of gas-gypsum. The best results were shown by the gas-gypsum, which included fiberglass. Glass fiber was pre-ground to a specific surface of 190-240 m² / kg, in order to improve further the physico-mechanical properties of gas-gypsum.

Abstract: The stability of ettringite as high-watery mineral is highly dependent on the ambient temperature. Under standard laboratory conditions, onset of decomposition of this phase occurs at temperature of 80°C already and the theoretical temperature of the complete decomposition of ettringite is 180°C. Ettringite decomposition can occur at significantly different temperatures under humidity conditions other than the laboratory ones. Within the work verification of the possibility of synthetic preparation of ettringite by direct addition of aluminum sulfate, Al₂(SO₄)₃·18H₂O, and calcium hydroxide, Ca (OH)₂, as an alternative method to the yeelimite hydration procedure was carried out. The stability of the resulting systems was examined in two different environments, namely in a laboratory environment and the environment of saturated water vapour. The phase composition of the samples was determined by X-ray diffraction (XRD) analysis, thermal analysis and scanning electron microscopy (SEM).

Abstract: The objective of this work is to evalute the coagulation-flocculation efficiency of the aluminum sulfate for the elimination of aromatic organic molecules (phenylalanine and catechol) in the presence of mineral salts of Ca²⁺ , SO₄^2- and PO₄^3-.Trials were conducted on the one hand on synthetic solutions of aromatic compounds in distilled water enriched by ions of calcium, sulphates and phosphate ions introduced in various forms (CaCl₂ ; CaSO₄ ; MgSO₄ ; Na₂SO₄ ; NaH₂PO₄ ; KH₂PO₄), and on the other hand on Algerian drilling waters of different physicochemical characteristics. Results show that the addition of minerals salts seems to improve the yields of elimination of aromatic compounds tested and affects the optimal pH range of coagulation. The application of this process on mineralized waters (water drilling) leads to improve yields compared with those obtained in distilled water. It was also found that the process efficiency depends on the nature and the number of functional groups on the molecules and on their position relative to each other. The main mechanisms would be either a physical adsorption ,an exchange of ligand or a complexation on the floc surface of aluminum hydroxides.

Abstract: Based on orthogonal design method, a kind of alkali-free liquid accelerator is successfully developed by adopting aluminum sulfate, DL-Lactic acid, triethanolamine, glycerol, phosphoric acid and other raw materials. The initial setting time of the accelerator is 2min50s, and final setting time is 6min30s. The compressive strength ratio of 28 days is 103.5%. All the indices meet the first class requirements in Flash setting admixtures for shotcrete (JC477-2005). It is also provided with better adaptability. Finally XRD testing method is adopted to reveal the fast-setting mechanism of alkali-free accelerator.