Effect of AlF3 Production Waste on the Properties of Hardened Cement Paste

Abstract

The possibility to use by-product SiO₂·nH₂O (often called AlF₃ production waste) in cement casting has been attracting the interest of researchers for many years, although high content of fluorine makes the use of amorphous SiO₂ problematic. Finding the way of utilizing waste products is a very important research topic at the moment. In this study AlF₃ production waste was investigated as the basic ingredient of a new pozzolanic material. The goal of this study is to investigate the possibilities of using AlF₃ production waste, washed in ammonia solution, in cement stone specimens. Chemically treated silica gel additive was proved to reduce the amount of Ca(OH)₂ and CaCO₃ in hardened cement paste samples. Experimental research has revealed that the density in hydrated samples reduces from 2220 kg/m³ to 2030 kg/m³ with the increase of silica gel content from 0 % to 35 %. The compressive strength of samples containing 10 % of silica gel additive increased by 8.04 % compared to the samples without the additive. SiO₂ additive used at 10 % and 20 % increased the maximum hydration temperature. In this case, the additive modifies the hydration kinetics.

DOI: http://dx.doi.org/10.5755/j01.ms.18.2.1925