Journal
MATERIALS CHEMISTRY AND PHYSICS
Volume 248, Issue -, Pages -Publisher
ELSEVIER SCIENCE SA
DOI: 10.1016/j.matchemphys.2020.122938
Keywords
Geopolymer materials; Thermally untreated phosphate sludge; Compressive strength; Apparent porosity; Microstructure
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Funding
- OCP (OCP Foundation)
- RD OCP
- Mohammed VI Polytechnic University
- National Center of Scientific and technical Research CNRST
- Ministry of Higher Education, Scientific Research and Professional Training of Morocco MESRSFC [MAT-MOS-01/2017]
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In the present work we investigate the possibility of reusing phosphate sludge, which is considered as a mining by-product from beneficiation plants of the Moroccan phosphate rocks (OCP, Youssoufia), through the geopolymerization process. This process allows to evaluate the alkaline behaviour of thermally untreated phosphate sludge (UPS) as a partial replacement of metakaolin. The geopolymers were synthesized with various activator modulus (Ms = 1.40, 1.30, 1.24, 1.20, and 1.15) made from a mixture of different alkaline (NaOH and KOH) solutions and sodium silicate. The effect of 0-60% untreated sludge (UPS) powder in metakaolin based geopolymer materials cured at 60 degrees C was investigated. Compressive strength and apparent porosity were determined after 28 days of curing and the reaction products were tested by different techniques including: X-Ray Diffraction (XRD), Fourier Transformed Infrared spectroscopy (FTIR), thermal gravimetric analyses (TGA) and Electron microscope scanning coupled with energy dispersive spectroscopy (SEM-EDX). For up to 50% of UPS, physical properties of the hardened products are induced, especially when the activator modulus (Ms = 1.30) is used. In these blends, the presence of UPS is favorable to ensure the better connectivity between grains in the system. In fact, the sludge has been suggested to have a dual role, it has a filler effect and/or a small precipitation of Ca-bearing phases co-existing with (Na, K)-A-S-H type gel.
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