ACTIVATE FLY ASH REACTION USING BAUXITE RESIDUE IN BLENDED CEMENT

Transcription

1 GEMM ACTIVATE FLY ASH REACTION USING BAUXITE RESIDUE IN BLENDED CEMENT Marcelo Montini (PhD student) 1 marmontini@outlook.com Xuerun Li 2, José de Anchieta Rodrigues 1, Romano, R.C.O 3, Rafael G. Pileggi 3, Karen Scrivener 2 1 Department of Materials Science and Engineering, UFSCar, São Carlos, Brazil 2 Department of Materials Science and Engineering, EPFL, 1015, Switzerland 3 Department of Civil Construction, USP, São Paulo, Brazil 1

2 Summary 1) Background Motivation Objective 2) Main results Raw material characterization Chemical reaction Microstructural development 3) Conclusions 2

3 Background 3

4 Project is connected to solid network of partners GEMM Laboratory of Microstructure and Eco-efficiency of Materials DEMA - UFSCar Materials Microstructure Engineering Group (GEMM) Laboratory of Construction Materials (LCM) Alumar and Alcoa Poços, Brazil Technology Delivery Group, Australia Alcoa Foundation, USA 4

5 Motivation Global CO 2 and GHG emissions per sector Paris Agreement (2015) Max. 2 o C by

6 Motivation: 45% of carbon emission reduction at cement sector The cement industry currently represents about 7% of the carbon dioxide (CO2) emissions globally * IEA/CSI. Technology Roadmap Low Carbon Transition in the Cement Industry

7 Motivation: SCM may contribute with 37% of cumulative CO 2 emission reduction ( ) CO 2 Precalcining/Clinkerization 5 6 Blending/Grinding 8 9 Slag Fly ash Clay Low Carbon * IEA/CSI. Technology Roadmap Low Carbon Transition in the Cement Industry Supl. Cementitious Material (SCM) Clínker CaCO 3 CaO + CO % of total CO 2 Clínker SCM 7

8 Potential Products with BR as SCM (> 9 years of experience) Portland Cement Final Products Used as SCM 1.1 Only BR (pure/calcined) 1.2 BR + BFS 1 2 Mortar Tile * * * Bauxite Residue BR + FA Concrete Brazil 8

9 Why to use the combination of BR with FA? FA is one of the most important industrial waste, mainly in China and India The utilization of blended cement is already a global reality and its tendency is to grow in the future Alumar produces both waste (pratical point of view) The hypothese is that combination could lead some advantages: Improvement of mechanical properties by chemical reaction or packing optimization Reduction of Na free (from BR) by chemical reaction (formation of stable product like sodium silico aluminate). It would be positive for durability! 9

10 Objective and key questions To investigate the activation of fly ash (FA) by bauxite residue 1) Does BR work as regular SCM? 2) How does the combination of BR/FA interfere on clinker hydration? What does it depend on? 10

11 Materials preparation: BR from Alumar and Commercial FA (Brazil) BR: sample was produced by using a filter press pilot. It was dried at 100 o C and ground for 15 min. BR (from last washer) 40% solid content Pilot filter press BR cake (70% solid content) Dried BR Operational parameters*: Φ 0.38 x 0.40 m Rotacional speed: 47 rpm; Specific charge: 32%; sample/ball (w/w): 10 Ground BR * Ene. G; The grinding charge of rotary mills. The Annals of University of Galati. Fascicle XIV. Mechanical Engineering. ISSN (2007) 11

12 Characterization of raw materials Parameters (%) CPV Cement** BR IFA SiO Al 2 O Fe 2 O CaO TiO MgO 1.06 < MnO < SO Cl <0.001 Na 2 O K 2 O Na 2 O Equivalent* Loss on Ignition * Na 2 O K 2 O/** CPV has 5% of limestone/br = bauxite residue; IFA = Intercement fly ash High Alkali cement FA type F OPC IFA BR SA (m 2 /g) Density (g/cm 3 ) 14X D 10 (µm) D 50 (µm) 27 3 D 90 (µm) X 12

13 1) Does BR work as regular SCM? 13

14 R 3 calorimetry method for BR and IFA Calorimetry 12 days at 40 o C BR IFA Quartz SCM (g) Water (g) Quartz (g) Al 2 O 3 - % SO 3 - % SO 3 /Al 2 O Gypsum (g) SO3 - % SO3/Al2O3 (adjusted) Portlandite (g) KOH (g) Water/SCM Water/Solids Paste (g) RB = bauxite residue; IFA = Intercement fly ash Snellings. R.; Scrivener. K. Rapid screening tests for supplementary cementitious materials: past and future. Materials and Structures (2016) 14

15 BR reacts only the beginning of hydration (R 3 test) Pozzolanic Reaction Hydrated Products CSH calcium silicate hydrate Ettringite = C 6 Al 2 (OH) 12 (SO 4 ) 3 26H Afm = 3C 4 Al(SO 4 )12H or C 4 Al(CO 3 )12H Snellings. R.; Scrivener. K. Rapid screening tests for supplementary cementitious materials: past and future. Materials and Structures (2016)

16 2) How does the combination of BR/FA interfere on clinker hydration? 16

17 Studied Mixes Wt.% Clinker Anhydrite Calcite BR Added gypsum IFA 30IFA 3.5BRBR26.5IFA 7BR23IFA 15BR15IFA 30BR

18 Calorimetry of OPC/BR/IFA Mixes (20 C and w/c = 0.4) Glossary: C = CaO; S = SiO 2 ; Al = Al 2 O 3 ; H = H 2 O; Ettringite = C 6 Al 2 (OH) 12 (SO 4 ) 3 26H Afm = 3C 4 Al(SO 4 )12H or C 4 Al(CO 3 )12H Could cumulative heat increase be translated into compressive strength improvement? What is going to happen after 8 days? Note: normalized by cement mass Until 4 day: 3.5BR, 7BR, 15BR and 30BR > 30IFA Until 8 days: 3.5BR and 7BR >30IFA 18

19 Low BR content affects positively the compressive strength 1 day: BR increases the compressive strength 3.5-7% BR: strength is higher at 7 days but similar at 28 days than reference >7% BR: strength is lower than reference at 28 days < 3.5% BR: strength is higher than reference at 28 days

20 But, low addition of BR may have a significant impact on sustentability target? 20

21 The global incorporation of 1% of BR as SCM would surpass the IAI sustentability target for 2025 BR addition (wt.%) 1% 2% 3% BR reuse (MM ton/year)* BR reuse (%) CO 2 emission reduction (M Mton/year)** Notes: * a) Global cement production: 4 bi ton/year; b) global BR generation: 120 Mton/year; c) CO 2 rate emission (Kg CO 2 /ton cement): 700 ** cement plant Sustainability goal for BR reuse: 20% by 2025 (International Aluminium Institute IAI) 1) LAC RD&I report (Cement industry overview: Bauxite Residue utilization in cement production plants nearby Alcoa Refineries); 2) Bauxite residue valorisation and best practices conference (2015) 21

22 Conclusions The reuse of 1-3% of BR into blended cement (with high alkali content) would be enough to overcome the global target sustainability of Alcoa and aluminum industry. The small addition of BR (up to 3%) leads to improvement of early and late compressive strength. This may be explained by synergic effect (physical and chemical) between BR and FA. This study did not still cover the rheological approach. Maybe, this approach could make feasible the incorporation of higher amount of BR 22

23 Long term proposal Create a technological alliance from academy, cement industry and aluminum industry to continuously identify and elucidate all the practical aspects required to make real the usage of BR in blended cement in replacement of clinker and other non renewable raw materials, therefore contributing to close the biggest sustainability gaps of the aluminum and cement industries: Landfill of solid residues CO 2 emissions and Raw material scarcity 23

24 Acknowledgement Prof. Rafael Pileggi and Dr. Cesar Romano from LME-USP Prof. José de Anchieta from GEMM-UFSCAR Prof. Karen Scrivener and Dr. Xuerun Li from LMC-EPFL Dr. Jorge Gallo Lance Myers and David Cooling from Alcoa Alcoa Foundation by financial support 24

25 Thank you! 25