Effect of elevated temperatures on alkali-activated tungsten mining waste based materials

Center of Materials and Building Technologies (C-MADE), Department of Civil Engineering and Architecture, University of Beira Interior (UBI), 6201-001 Covilhã, Portugal

^* Corresponding author: rehnheta@gmail.com

Abstract

Generally, alkali-activated materials (aka geopolymers) present good behaviour at high temperatures, but previous studies of geopolymers under elevated temperatures are, in most cases, focused on metakaolin or fly ash based geopolymers, making the information on geopolymers with mining waste mud almost inexistent. In this paper, were analysed geopolymers with different combinations of mining waste mud, waste glass powder, metakaolin and expanded cork in a total of 15 different mixtures using sodium hydroxide and sodium silicate as alkaline activators. Materials particle size used is under 500 μm for mining waste mud, waste glass powder. Some mixtures also included expanded granulated cork with particle size between 2 to 4 mm. Ten samples with 40 × 40 × 40 mm dimensions were used for the compression test, one sample for the TGA test, and one cube (100 × 100 × 60 mm) with a frustoconical hole (50 mm deep) and a 100 × 100 × 25 mm cover, for the cup test. All the mixtures were cured for 24h at a temperature of 60 °C before being demoulded, and left at room temperature until they reach 7 days to be tested. On the 7th day, of each mixture, samples were placed in a static furnace before the compression test submitted to a temperature of 800 °C during 2h. Then, the compression test was performed and the values before and after exposure to high temperatures were compared. Were recorded maximum gains of 724% and maximum losses of 100% in the compressive strength. This preliminary result shows the potentials of mining waste alkali-activated materials for elevated temperatures applications.