The Processing of Citrogypsum for Obtaining Modified Gypsum Binders and Composite Materials on their Basis

Abstract

The article considers a method of recycling citrogypsum – the сіtric acid production waste. A modified gypsum binder was obtained by means of dehydration of citrogypsum suspension and adding a modifier - polyacrylamide (PAA) - to it in conditions of autoclave treatment. The application of PAA as a modifying admixture causes the necessity to reduce the water-gypsum ratio (W/G) of the mix in order to prevent lamination at the molding product forming; at the same time, to provide the necessary flowability of the mix the introduction of plasticizing admixtures is needed, or the application of the harsher moulding mixtures or pressing technologies. For cylindrical samples, obtained by the compaction method at W/G=0.25 and the specific compacting pressure 20МPа, the optimal content of polyacrylamide as a modifying admixture amounts to 2% of the initial citrogypsum weight. This allows increasing the compression strength of the ready samples by more than 5 times. The samples, produced on the basis of modified gypsum binders, are characterized with high water resistance – the softening coefficient amounted to over 0.8.

Experimental study for Gypsum Materials Enhanced by Compound Additives Based on Nano-Silica

“…To solve this problem, various types of mineral additives are used, including products of technological products such as slag, ash and sludge of various origins [1][2][3]. Studies [4][5][6] indicate that the most effective method is to introduce silica containing additives that contribute to the formation of sparingly soluble products in the gypsum stone structure, preventing calcium sulfate from dissolving in water and providing strength and water resistance products. The efficiency of introducing these additives directly depends on the particle size of the modifier.…”