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Peculiarities of hydration of cement paste with addition of hydrosodalite

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

Materials Science Poland

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2007

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Vol. 25, No. 3

627--635

EN

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%.

2

Synthesis and hardening of fluoralinite cement

Kantautas A., Palubinskaite D., Vaickelionis G.

Materials Science Poland

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2006

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Vol. 24, No. 2/1

385--393

EN

In this paper the synthesis of fluoralinite cement and its hydration properties are presented. It was determined, that fluoralinite has been obtained after 4 hrs at 1100 °C temperature without difficulty, by using in the initial composition of 0.89 % Al2O3, 1.78 % MgO and 0.89 % Fe2O3 additions. Specimens, formed from fluoralinite clinker and grinded sand (fluoralinite clinker and sand mass ratio 1:3) and hydrothermal cured at 175 °C for 4 hrs, had the biggest strength (4.68 MPa). Thus, fluoralinite cement is usable for hydrothermal curing articles. X-Ray analysis has shown, that, while hardening of the mix of fluoralinite and quartz sand for 28 days in normal conditions, quartz, tobermorite gel, portlandite Ca(OH)2 and CaF2 prevail in the samples. Whereas this mix hardens in hydrothermal conditions, calcium hydrosilicate C - S - H (I) and Ca(OH)2 form.

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Influence of tribomechanical milling and activation of primary mixtures on the synthesis of calcium silicate hydrates

Palubinskaite D., Kantautas A.

Materials Science Poland

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2006

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Vol. 24, No. 2/1

395--403

EN

Tobermorite group minerals with double [Al3++Na+] substitution, using non grind row minerals mixture and grind mixtures in the colloidal mill were syntheses. Calcium silicate hydrate synthesis is going on more intense, when dry primary mixtures ground in a colloid mill are taken, because, having the same synthesis conditions, the compositions of higher crystal degree are synthesized. In this case after 24 h tobermorite forms itself. It is thought, that grinding in a colloid mill a mixture of CaO; SiO2 and Al2O3 some activation centres are induced, which later in the process of hydrothermal processing activate the process of synthesis run. It is reasonable to grind in colloid mill the dry component mixtures, used for synthesis of tobermorite, before hydrothermal processing, until optimum. In the research conditions given the tobermorite formed more intense when original surface was less: S = 547 m2/kg. It is not expedient to use mixtures of smaller primary materials, because stabilizing influence of C-S-H(I) on over forming kinesis of tobermorite displayed itself.

4

The synthesis of hydrosodalite and its use in mortar technology

Sasnauskas V., Palubinskaite D.

Materials Science Poland

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2005

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Vol. 23, No. 3

793--801

EN

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.