Effect of immersion in water partially alkali-activated materials obtained of tungsten mine waste mud

Alkali-activated binders can be obtained using several sources of alumino-silicate materials, from calcinated clays, like kaolin, to industrial by-products, such as fly ash and, more recently, to calcinated waste mud from mining activities. The technology to obtain alkali-activated binders, also designated as geopolymers, is gaining increasing interest, since, in some cases, the properties of geopolymeric materials are superior to other existing cementitious systems. The research presented in this paper intends to deepen the knowledge regarding the properties of geopolymeric materials obtained using tungsten mining waste mud, particularly to study its behaviour after being immersed in water. However, in the current work, focus is given to follow compressive strength results in partially alkali-activated samples immersed in water, during different curing periods of time. Energy Dispersive X-ray Spectroscopy (EDS), X-ray Diffraction (XRD) and Fourier Transform Infrared Spectroscopy analysis (FTIR) were also utilised to investigate changes in the microstructure at different conditions of water immersion. A significant decrease in compressive strength occurring after 24 h of immersion in water was found out, of specific partially alkali-activated materials, despite of its initial high compressive strength after 35 days curing, at different temperatures.

► Partially alkali-activated specimens disintegrated after been immersed in water.
► Disintegration of materials occurred simultaneously with an increase of water pH.
► A specimens’ compressive strength decrease occurred after 24 h immersion.
► This behaviour might be due to deficient geopolymeric reaction.