Production and characterization of geopolymers containing electric arc furnace dust (EAFD) for hazardous metals sequestration

The present research deals with the production and characterization of geopolymers prepared by mixing metakaolin with sodium silicate, sodium hydroxide solution and different amounts of electric arc furnace dust derived from the production of carbon steel, to be used by the construction industry. Specimens with compositions containing 90, 80, 70, 60 and 50 g of metakaolin and respectively 10, 20, 30, 40 and 50g of electric arc furnace dust powder were prepared. A blank composition containing metakaolin, sodium silicate, sodium hydroxide solution and free from electric arc furnace dust were also prepared for comparison. After production and hardening, all samples were characterized regarding compressive strength and water absorption. Hardened samples with compositions containing 10 and 30g of electric arc furnace dust were then submitted to a release test in order to evaluate the heavy metals elution. It has been observed that the addition of electric arc furnace dust worsens the pastes workability during their production in this way limiting the amount of electric arc furnace dust which may be added to the geopolymeric matrix. However, samples containing 90 g of metakaolin and 10 g of electric arc furnace dust still maintain fair compressive strength (about 27 MPa), low water absorption (about 28 %) and display limited elution of heavy metals. An additional thermal treatment of 1h at 700 °C, performed to induce sintering of the geopolymeric composites and therefore to reduce their porosity, did not lead to materials with improved performances.