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Hydrosodalite ion exchange in saturated Ca(OH)2 solution

100%

Vaičiukyniene D. , Baltakys K. , Kantautas A.

tom Vol. 27, No. 2

417--426

The possibility of substituting Na+ ions contained in pure hydrosodalite crystal structure with Ca2+ ions in saturated Ca(OH)2 solution has been examined in the temperature range from 25 °C to 95 °C. It was found that temperature strongly influences the hydrosodalite ion exchange: upon increasing temperature only by 5 °C (from 25 to 30 °C) Ca2+ the time required for Ca2+ions to be incorporated within the hydrosodalite crystal structure is reduced by the factor of 3. With the increase of temperature from 45 °C to 65 °C almost all the Ca2+ ions, initially contained in the Ca(OH)2 solution, become incorporated in the hydrosodalite structure after 5 min However, high temperature has an adverse effect on the sorption process (Ca2+ ions will not be incorporated within the hydrosodalite structure before 10 min have elapsed). Partly reversible ion exchange reactions of hydrosodalite are characteristic at temperatures higher than 30 °C). The structure of hydrosodalite crystals remains stable when performing ion exchange reactions at 25-95 °C temperature.

The synthesis of hydrosodalite and its use in mortar technology

80%

Sasnauskas V. , Palubinskaite D.

tom Vol. 23, No. 3

793--801

The conditions of low-temperature hydrothermal synthesis of zeolites from AlF3 production waste technogenic silicagel polluted with admixtures of fluorides, were analyzed. It was determined that AlF3 admixture encourages the formation of hydrosodalite. When using technogenic silica gel, crystal zeolite hydrosodalite was synthetized. The reaction was conducted under hydrothermal conditions, under atmospheric pressure at 90oC temperature for 0.5, 1 and 2 hours. The best molar ratio of the components Na2O : Al2O3 : SiO2 : H2O was 2 : 0,02 : 1 : 10. Lignosulphonic plasticiser (LST) was modified with synthetized hydrosodalite. The binding duration of cement paste of normal consistence with modified LST plasticiser decreased up to 40/395 min. (at 0.25% content of admixture) and 80/150 min. (0.75%), as compared with that of mortar non-modified with LST plasticiser, where the binding duration was equal to 65/475 min. (0.25 %) and 105/150 min. (0.75%). Larger compression strength of cement grout with modified LST plasticiser after 3, 7 and 28 days of hardening was obtained: 12.61; 21.52; 25.49 MPa (at 0.25 % content of addition), as while that mortar with nonmodified LST plasticiser 6.04; 9.63; 22.69 MPa compression strengths of specimen, respectively.

Peculiarities of hydration of cement paste with addition of hydrosodalite

80%

Skripkiunas G. , Sasnauskas V. , Daukšys M. , Palubinskaite D.

Materials Science Poland

2007

tom Vol. 25, No. 3

627--635

A synthetic zeolite - hydrosodalite was used as a hydraulic additive for hardened cement paste, and the influence of this additive on the hydration and other properties of the system was determined. Hydraulic activity of zeolite has been examined, X-ray diffraction, DTA and IR analysis of the hardened cement paste with zeolite additive have been carried out. The results have shown that the additive has a high hydraulic activity (the content of bound CaO - 370 mg/g). The addition of hydrosodalite reduces the content of Ca(OH)2 in hardened cement paste which transforms into calcium zeolite - gismundite. The density of the hardened cement paste with the addition of hydrosodalite after 3, 7 and 28 days of curing decreases by about 11%. This predetermines a decrease in the compressive strength of the hardened cement paste. The compressive strength after 3 days of curing decreases by about 70%, after 7 days of curing - by 66%, and after 28 days of curing - by about 65%.