Hydrate phase assemblages for high performance low clinker cements

Transcription

1 Hydrate Hydrate phase phase assemblages assemblages for for high low h performance clinker fit for low purpose clinker p cements cements Duncan Duncan Herfort Herfort Cementir Cementir Holding Holding

2 Introduction Can we replace 50% clinker by a non-calcareous pozzolana (e.g. class F FA) for same concrete performance? Hydrate phase assemblages for high h performance low clinker cements At first glance the answer is no, because the maximum replacement with a non-calcareous pozzolana for same strength is c. 25%, and Except for N.AmericaDuncan production Herfort of industrial SCMs falls well short of this in any event Cementir Holding Solutions to overcome this include developing natural pozzolana including calcined clays, the synergy between limestone and alumino silicate pozzolana for replacement up to 50%, and alkali activation for replacement higher than 50%

3 4 cement pro oduction pa 3 Improved improved kiln kiln efficiency, use of bio fuels biofuel,n.gas & natural gas where (0.93 practicable 10 9 t CO 2 ) 40% SMC for same concrete 40% SCM for same concrete performance performance ( t CO 2 ) Glo obal CO2 emi ission from 10 9 tonne 2 1 Currently 25% is about the limit for Serie1 non calcareous SCMs 1/51/3 of of RM RM COCO2 2 recarbonated ( t CO 2 ) 2/5 of CO 2 emissions captured and 1/4 stored of CO2 (0.83 emissions 10 9 t i CO stored 2 ) and captured

4 28d strength hs, MPa clinker replacement, %

5 SiO 2 silica gel 20% Silica fume clays pozzolans C SH y C-S-H ss C 1.7 SH x 70% GBFS 35% basaltic pozzolan 25% granitic pozzolan 25% calcined clay or PFA stratlingite CH C 3 A.CS.H 12 C 3 A.CC.H 12 C 3 A.3CS.H 32 gibsite CaO Al 2 O 3 C 3 A Portland cement

6 Max clinker replacement by non calcareous pozzolana for equal concrete performance c. 25% silica gel 20% Silica fume clays pozzolans C SH y C-S-H ss C 1.7 SH x 70% GBFS 35% basaltic pozzolan 25% granitic pozzolan 25% calcined clay or PFA stratlingite CH C 3 A.CS.H 12 C 3 A.CC.H 12 C 3 A.3CS.H 32 gibsite CaO Al 2 O 3 C 3 A Portland cement

7 Max clinker replacement by noncalcareous pozzolans for equal concrete performance c. 25% silica gel Availability c. 10% 20% Silica fume clays pozzolans C SH y C-S-H ss C 1.7 SH x 70% GBFS 35% basaltic pozzolan 25% granitic pozzolan 25% calcined clay or PFA stratlingite CH C 3 A.CS.H 12 C 3 A.CC.H 12 C 3 A.3CS.H 32 gibsite CaO Al 2 O 3 C 3 A Portland cement

8 World wide availability of Supplementary Cementitious Materials x Metakaolin Rice husk ash Silica fume Burnt shale Natural pozzolana Blast furnace slag IEA production data published 2008: Cement 2500 tpa Fly ash 300 tpa Used in cement BF slag 220 tpa Reserve i.e. max 20% of cement Fly ash Limestone Cement Mill. tons/year

9 World wide availability of Supplementary Cementitious Materials x Metakaolin IEA production data Rice husk ash published 2008: Potentially Silica fume 25% for same concrete performance, but only 10% Burnt shale availability. Solution is to exploit existing landfilled PFA, natural pozzolana, or calcined clay Natural pozzolana Blast furnace slag Fly ash Cement 2500 tpa Fly ash 300 tpa Used in cement BF slag 220 tpa Reserve i.e. max 20% of cement Limestone Cement Mill. tons/year

10 World wide availability of Supplementary Cementitious Materials x Metakaolin IEA production data Rice husk ash published 2008: That Silica fume still leaves us well short of our target of 50% replacement Burnt shale Natural pozzolana Blast furnace slag Fly ash Limestone Cement Cement 2500 tpa Fly ash 300 tpa Used in cement BF slag 220 tpa Reserve i.e. max 20% of cement Mill. tons/year

11 strength hs, MPa 28d clinker replacement, %

12 The carboaluminate reaction suggests a way out. strength hs, MPa 28d clinker replacement, %

13 gypsum CaSO 4 + CSH + CH + FH 3 + pore solution ettringite thaumasite monosulfate Ms-ss Reduced porosity Increased porosity C 4 AH 13 C 3 A Hemicarbonate Monocarbonate calcite CaCO 3

14 higher aluminate content = higher strengths 15 compressive strength measured nd ] porosity a trength [%] 10 5 increase relative change of com pressive st total porosity calculated decrease amount of CaCO 3 added [wt.-%] Very good correlation between predicted changes of relative porosity and measured compressive strength

15 Hydrate phase assemblages for high h performance low clinker cements Limestone and calcined clay Duncan Herfort Cementir Holding

16 d stren ngth, MPa % calcined mixed clay Metakaolin calcined Na bentonite 0 0,2 0,4 0,6 0,8 1 clay content (wt. fraction of clay/(clay+limestone), clinker + gypsum constant at 65%)

17 d stren ngth, MPa % calcined mixed clay Metakaolin calcined Na bentonite 0 0,2 0,4 0,6 0,8 1 clay content (wt. fraction of clay/(clay+limestone), clinker + gypsum constant at 65%)

18 ete at con nstant m 3 concre trength ssion kg/m st CO 2 emis CEM I at same fineness - 18 % - 33% mixed clay Metakaolin 0 0,2 0,4 0,6 0,8 1 clay content (wt. fraction of clay/(clay+limestone), clinker + y ( y ( y ) gypsum constant at 65%)

19 ete at con nstant m 3 concre trength ssion kg/m st CO 2 emis CEM I at same fineness - 18 % Most studies have shown that 40% replacement is about the limit - 33% before the supply of Ca is exhausted. To go further other hydrate phases need to form. mixed clay Metakaolin 0 0,2 0,4 0,6 0,8 1 clay content (wt. fraction of clay/(clay+limestone), clinker + y ( y ( y ) gypsum constant at 65%)

20 SiO 2 silica gel 20% Silica fume clays pozzolans C SH y C-S-H ss C 1.7 SH x 70% GBFS 35% basaltic pozzolan 25% granitic pozzolan 25% calcined clay or PFA stratlingite CH C 3 A.CS.H 12 C 3 A.CC.H 12 C 3 A.3CS.H 32 gibsite CaO C 3 A Al 2 O 3 Portland cement Ca needed to form AFm, AFt phases

21 ete at con nstant m 3 concre trength ssion kg/m st CO 2 emis CEM I at same fineness - 18 % Calcined clays normally require more water for the same consistency - 33% and therefore more cement for the same strength. However, this can be overcome by the correct sequence of mixing with water reducers. mixed clay Metakaolin 0 0,2 0,4 0,6 0,8 1 clay content (wt. fraction of clay/(clay+limestone), y clinker + gypsum constant at 65%)

22 cement without SP cement + SP early addition (reference) cement + SP late addition 0.6% SP w/b = % replacement Shea ar Stress (P Pa) Shear Rate (s -1 )

23 Pa) She ear Stress ( cement early addition cement+cb early addition cement+cb late addition Shear Rate (s -1 )

24 Alkali activated calcined clay and portland cement Natrolite Na 2 Al 2 Si 3 O 10 2H 2 O

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26 STRUCTURAL EVOLUTION ASSESSMENT Increasing NS (0 16%) 40% clinker, MK/(MK+ls) ratio = 0.96, sodium sulfate content = 0, 4, 10, 16% Constant water/binder ratio of 0.57 Futurecem Workshop 7 Aalborg August

27 EFFECT OF MK/LIMESTONE RATIO ON STRUCTURE X-RAY DIFFRACTION 90 DAYS OF CURING 40% CLINKER MK/(MK+ls) ratio: a) 0.80 and b) 0.96 Futurecem Workshop 7 Aalborg August

28 STRUCTURAL EVOLUTION ASSESSMENT Aluminosilicate gel 27 Al MAS NMR 40% CLINKER 14.1T, R = 13.0 khz 180 days 1 Third aluminate 90 days 28 days AFm phases AFt phases Al(IV) in C-S-H 7days NS = 0% NS = 16% Futurecem Workshop 7 Aalborg August

29 4 3 STRUCTURAL EVOLUTION ASSESSMENT 2 1 Aluminosilicate gel 27 Al MAS NMR 40% CLINKER 14.1T, R = 13.0 khz Sodium sulfate is an effective activator in mixed CSH 180 zeolitic days systems if the right balance can be found for a sufficiently i 1 high ph for activation and the content of 2 90 days Na needed to balance Al in the framework 3 silicates (must be 1:1). 28 days 4 Third aluminate AFm phases AFt phases Al(IV) in C-S-H 7days NS = 0% NS = 16% Futurecem Workshop 7 Aalborg August

30 Conclusion By combining limestone and alumino silicate pozzolana (FA, calcined clay etc.), the levels of clinker replacement for the same concrete performance can be extended from about 25% to 40%. F f th l l f l t lk li f ti ti For further levels of replacement, alkalis for activation and stabilisation of framework silicates are needed.