Pozzolanic and Cementing Activity of Raw and Pyro-Processed Saudi Arabian Red Mud (RM) Waste

This paper investigates the composition, properties and reactivity of a red mud waste generated in Saudi Arabia with view to find alternative materials replace construction binders high environmental impact. The phase transformation triggered by sintering RM up 1000°C is determined thermal X-Ray Diffraction analyses. Reactivity investigated chemical physical methods including Chapelle test, setting times, mechanical index microscopy. clearly pozzolanic, its activity mainly due reaction feldespathoids formation zeolitic feldspathoid-based hydrates. positive effects treatment are seen below 750°C, include loss water zeolite/feldespathoids, destruction crystal structures clay minerals inherited form parent bauxite. negative evidenced over decrease specific surface area, devitrification formation, whereby active transition aluminas fedespathoids/zeolites (mainly cancrinite) transform into nepheline, tricalcium aluminate (C3A) gehlenite. Despite occurrence C3A gehlenite sintered at 1000°C, pozzolanic hydrates that cause strength development greater lower temperature. optimum enhances lies c.400°C, as highest lime combination, greatest fastest set. consists gibbsite boehmite, from bauxite, cancrinite, chantalite sodalite formed during Bayer process. Feldespathoids have formed, instead zeolites, available silica alkali content RM. quick -CaO -, added twice refining process, has transformed original goethite hematite, produced cancrinite. SiO2 alkalinity, an abundant area for reaction. chloride carbon contents low, no toxicity inferred chemistry.