Investigations of geopolymeric mixtures based on phosphate washing waste

The extraction of the phosphate ore produces a high amount of waste causing serious environmental problems. This waste, termed as phosphate washing waste, was filtered and dried at 105 °C for 24 h to remove the water. The dried waste was milled and then sieved in a 100 ?m sieve. The resulting phosphates washing waste (PWW) particles size are below 70 ?m. The phosphate washing waste was calcined at 700 °C and 900 °C. Both calcined and uncalcined waste were investigated with X-ray fluorescence (XRF), X-ray powder diffraction (DRX), Fourier transform infrared (FTIR), simultaneous differential thermal and thermogravimetric analyses (DTA-TG) and particle size analysis. This waste was activated with sodium hydroxide (NaOH) and sodium silicate in order to produce geopolymeric materials. The influence of replacing PWW by 15% of metakaolin was also study. The results show that the highest compressive strength is obtained with metakaolin. The results also showed that compressive strength decreased with the increase of NaOH concentration.Gafsa Phosphate Company “CPG Tunisia” for providing us the phosphate washing waste sample and the Portuguese Foundation for Science and Technology (FCT) for the finance of the project UID/ECI/04047/2013