Effect of nacl on hydration of alkali-activated slag

Abstract

At present, seawater desalination seems to be the main and most feasible technology in order to satisfy the ever-increasing fresh water demand around the world. At the same time, it has become the most important non-natural water resource. However, the disposal of the brines generated by the desalination process poses significant environmental issues, due to the high concentrations of salts. This activity presents several environmental drawbacks and negative impacts on marine ecosystems, originated mainly by the discharge into the sea of the generated brine. To reduce the amount of RO/MD brine from seawater reverse osmosis that is disposed into the sea, by using it in a chlor-alkali process. This study investigates the alkali activated concrete which is mixed by granulated blast furnace slag from utilizing industry and alkali activator from electrolysis process using RO/MD brine. In addition, it has also been observed that alkali activator composition (NaOH, NaCl) generated by electrolysis and compressive strength according to concentration result in carried out to understand the effect of sodium chloride content on the alkali activated concrete. Higher concentration of NaOH of the alkali activated slag resulted in a faster reaction and higher compressive strengths during the initial day and after 28 days. Mixed with 2% NaOH and 4% NaCl showed down the early hydration and a lower compressive during the first days was observed. At 28 days, significant effects on the degree of hydration, compressive strength was same as the mixed with 3.5% NaOH and 2% NaCl. It is determined that hydrotalcite plays a dominant role in the remarkable chloride binding ability of slag concrete. Its finding provides strong indication that it is the hydrotalcite which is the main responsible agent that results in the resistance of slag concrete to chlorides. In addition, it is possible to improve the possibility of utilization recycle without separation of NaCl generated concentration through the role of Hydrotalcite curing the concrete.