Influence of pozzolanic properties of red mud waste and hydration products in the durability and retention of heavy metals in mortars

Author(s): E.P. Manfroi, M. Cheriaf, J.C. Rocha
Paper category: Conference
Book title: 2nd International conference on Microstructural-related Durability of Cementitious Composites
Editor(s): Guang Ye, K. Van Breugel, Wei Sun, Changwen Miao
Print ISBN: 978-2-35158-129-2
e-ISBN: 978-2-35158-123-0
Publisher: RILEM Publications SARL
Pages: 1431- 1440
Total Pages: 9
Language: English

Red mud (RM) is a waste from alumina industry generated by the Bayer process. The large quantity of red mud produced and its disposal are currently a worldwide environmental problem. In the present research, the pozzolanic properties of dry and calcined red mud at 600, 700, 800 e 900ºC were investigated by analyzing the consumption of calcium hydroxide, using differential thermal analysis and, using the methodology of Brazilian standard NBR 5752 of comparison of the compressive strength. The investigation of the compounds hydrated was carried out in pastes produced with 5 and 15% of red mud in replacing the cement, using X-ray diffraction and differential thermal analysis techniques. The assessment of the release of heavy metals from mortars produced with red mud and cement was investigated using non destructive testing of leaching by diffusion based in the Dutch standard NEN 7345. Compressive strength test was carried in mortars constituted by 5, 10 and 15% red mud in replacement of cement. The results showed that the red mud calcined at 600°C presents the best pozzolanic activity and, the compressive strength of mortars produced with this waste meet values in accordance with regulatory Brazilian standard. The analysis by X-ray diffraction and differential thermal analysis showed the formation of the hydration products CSH, hydrated silicates of aluminum and "hidrogarnets”. In the mortars produced with calcined red mud at 600ºC, that showed the best pozzolanic activity, there was the maximum retention of the chromium. The results showed that the pozzolanic reactions of the red mud with the cement compounds formed hydration products capable of encapsulating partly the heavy metals from red mud.

Online publication: 2013
Publication Type: full_text
Public price (Euros): 0.00

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