Efficiency of CFBC fly ash. material in structural concrete

Transcription

1 INSTITUTE OF FUNDMENTAL TECHNOLOGICAL RESEARCH POLISH ACADEMY OF SCIENCES WARSZAWA, POLAND Michal A. Glinicki Efficiency of CFBC fly ash as secondary cementitious material in structural concrete Anna Maria Workshop 2008

2 Contents 1. Terminology 2. Resources of CFBC fly ash 3. Characterization of CFBC fly ash 4. Partial replacement of cement in concrete -strengthefifciency - durability efficiency 5. Conclusions

3 1. Terminology Terminology CFBC fly ash = Circulating Fluidized Bed Combustion fly ash i.e. the solid residue from coal combustion in fluidized bed boilers in power plants, collected by electrostatic t ti or mechanical precipitation it ti of dust like particles in flue gases C stands for type of the boiler: Circulating CFBC technology allows to meet strict emission control regulations - clean coal technology. When the coal is burned in CFBC boiler with an addition of SO 2 sorbent (usually limestone) the capture of SO 2 takes place in situ. The solid combustion residues consist of coal ash and the products of desulphurization. Other possible names: - fluidized bed combustion byproducts solid residue from fluidized bed coal combustion

4 1. Terminology 2. Resources World primary energy production in 2004 coal Main producers of hard coal in 2005 Shares of different fuels in the world electricity production

5 1. Terminology 2. Resources GLOBAL FORECAST OF ENERGY DEMAND IN 2030 From 2002 to 2030: - the global demand for primary energy will increase by 60% - the world production of electricity will double FORECAST OF PRIMARY ENERGY DEMAND: shares of different fuels With the expected consumption, the proven reserves of fossil fuels will be sufficient for: coal : almost 200 years, oil : 35 to 40 years, natural gas : 40 to 50 years. The world is not threatened by the danger of coal shortage

6 1. Terminology 2. Resources Resources of CFBC fly ash in Poland coming in 2008/2009: new power generation unit 460 MW in Lagisza power plant world's biggest supercritical fluidized bed combustion boiler for hard coal efficiency 45%, Foster-Wheeler Power plant 2005 Ash production in thousands tonne bottom fly ash total ash E power Turow E+H power Zeran E+H power Czechowice Dziedzice E power Jaworzno II E+H plant Katowice E+H power Tychy E power Siersza E power Chorzow Total to compare: cement production in Poland (2007): tonne 53% 8% 1% 38% CEM I CEM II CEM III other

7 1. Terminology 2. Resources 3. Characterization Characterization of CFBC fly ash shape and grain size CFBC C FA CFBC FA Turow Katowice (lignite) (hard coal) grain size [ μm]: grain size [ μm]: mainly mainly 4-5 below 1 max 120 max 80 min below 1 min below 1

8 1. Terminology 2. Resources 3. Characterization Hard coal, various sources Chemical composition of cement and three CFBC fly ashes Test parameters Contents cement CFBC FA CFBC FA CFBC FA CEM I Warsaw Katowice Turow SiO 2, [% by mass] Al 2 O 3, [% by mass] Requirements of EN 450-1:2005 for fly ash for concrete the sum of contents SiO 2 + Al 2 O 3 + (Fe 2 O 3 ) >= 70 CaO, [% by mass] *) lignite Hard coal SO 3, [% by mass] not more than 3.0 Cl -, [% by mass] not more than 0.10 CaO free, [% by mass] not more than 1.0 or 2.5 and **) MgO, [% by mass] not more than 4.0 Fe 2O 3 3, [% by mass] Loss on ignition, [% by mass] Unburned carbon content by TGA-DTA, [% by mass] <= 5 : Category A 2-7: Category B 4-9: Category C *) the content of reactive calcium oxide 10.0% **) soundness : the expansion in accordance with EN not greater than 10mm

9 1. Terminology 2. Resources 3. Characterization Monitoring of CFBC fly ash composition variability CFBC flay ash Turow (lignite) CFBC fly ash Katowice (hard coal) Component Contents. %; date of delivery Contents. %; date of delivery Component LOI o C/1h LOI o C/1h SiO SiO Fe 2 O Fe 2 O Al 2 O Al 2 O TiO TiO CO CaO CaO MgO MgO SO SO Na 2 O Na 2 O K 2 O K 2 O Free CaO contents, % CFBC fly ash source Turow Katowice

10 1. Terminology 2. Resources 3. Characterization 4. Strength efficiency Concrete strength th development In four years numerous concrete mixes were manufactured at constant workability in pairs: pure cement mix and 20% cement replacement mix Materials used: cement CEM I 32.5R- the content t 350 kg/m 3 or 300 kg/m 3 CFBC fly ash from hard coal combustion aggregates: natural gravel 2-8mm, 8-16mm chemical admixture, water (+9% for CFBC FA mixes) Range of variability of chemical composition of CFBC fly ash: SiO 2 : %, Al 2O 3 : %, CaO: %, SO 3 : %, LOI: 5.6 do 10.2%

11 1. Terminology 2. Resources 3. Characterization 4. Strength efficiency 60 CUBE 50 COMPRESSIVE 40 STRENGTH 30 INCREASE WITH AGE strength [MPa] Compresive ,2 57,77 57,55 51,7 53,1 48,3 44,3 40,5 34,3 33,1 7D 28D 90D 365D 3Y 4Y Age of specimens [D-days, Y-years] R-72/2001 R-73/ % 28 days= 100% Age min max average 3 30,8 39,6 34,7 7 53,2 81,6 70, ,0 100,0 100, ,8 133,1 116, ,2 136,2 126,6 2 years 129,6 129,6 129,6 3 years 129,2 141,3 135,2 4 years 131,5 143,6 138,5 Compressive stre ength [MPa] ,5 43,5 43,5 33,0 46,9 56,0 53,7 58,6 58,7 67,1 57,5 68,2 R-28/2001 R-29/ % D 28D 90D 365D 3Y 4Y Age of specimens [D-days, Y-years]

12 1. Terminology 2. Resources 3. Characterization 4. Strength efficiency Strength efficiency factor α -efficiency factor for CFBC FA in comparison to cement s total mass of binder (at 20% replacement level) s = c + α p = c ( α ) p Feret s formula for compressive strength of concrete: f c strength of reference concrete f cpf strength f concrete with CFBC fly ash (20% cement replacement) f c = A c 3.1 c + w fc A = c 3.1 c + w ; f cpf A = 0.8c α 0.2c + 3,1 2,6 0.8c α 0.2c + + w s

13 1. Terminology 2. Resources 3. Characterization 4. Strength efficiency Strength efficiency factor (variability during 4 years) co oefficient α 2,5 2,0 1,5 1,0 0,5 0,0 Variable sources of hard coal! alpha_90 alpha_365 0,4 42 0,4 45 0,4 48 0,5 50 0,5 51 0,5 51 0,4 49 0,5 57 0,5 54 0,5 52 0,5 52 0,4 49 0,4 49 0,5 50 0,4 43 0,5 52 water to cement ratio α efficienc facto fo CFBC FA in compa ison to cement α -efficiency factor for CFBC FA in comparison to cement α at 90 days: from 0.85 to 2.46

14 1. Terminology 2. Resources 3. Characterization 4. Strength efficiency Variability of standard mortar strength Regular quality control testing on standard cement mortars and mortars with CFBC FA replacing 20% of cement Materials used: cement CEM I 32.5R CFBC fly ash from hard coal combustion standard sand 0-2mm water w/c = 0.5; about 9% more water in CFBC FA mortars at equal consistency Compressive strength of mortars at 28 and 90 days Tested regularly at 10 days interval for 2 years

15 1. Terminology 2. Resources 3. Characterization 4. Strength efficiency Strength efficiency factor on mortars -variability during 2 years 2,5 Variable sources of hard coal! ent 2,0 average α: 1.12 at 28 days 1.20 at 90 days pha coeffici al 1,5 1,0 0,5 alpha_28 alpha_90 0, test t number α -efficiency factor for CFBC FA in comparison to cement s total mass of binder (at 20% replacement level) s = c + α p = c ( α ) p

16 1. Terminology 2. Resources 3. Characterization 4. Strength efficiency 5. Durability efficiency - XC XC Durability: air permeability of concrete Torrent air permeability test method specimens: slabs 500x500x100mm (5 measurements each) curing: in 95% RH/20C for 56 days then storage in dry laboratory conditions Concrete mixes 100,00 at equal workability : 1. cement CEM I only 10,00 2. cement CEM I 80%+ CFBC FA Katowice 20% 1,00 3. cement CEM I 80%+ CFBC 0,10 FA Turow 20% kt [10^ ^-16 m2] CEM only CFBC FA- hard coal CFBC FA - lignite water-reducing admixture 0,01 bazalt aggregate max.16mm (not regular gradation) water to cement ratio 0, indoor exposure time [days]

17 1. Terminology 2. Resources 3. Characterization 4. Strength efficiency 5. Durability efficiency - XF XF Durability: air void system in concrete Concrete mix design: constant water to binder ratio of 0.42 constant slump of 80 ± 20 mm constant air-void content of 6±1% Materials: -cement only -CFBC FA Warszawa (FLW) at 20%, 30% and 40% replacement -CFBC FA Katowice (FLW) at 20%, 30% and 40% replacement Basalt Basalt Mix Type of Cement Additive Sand 2-8- Water HRWR AEA additive 8mm 16mm Content [kg/m 3 ] l /m 3 l /m 3 CEM I none FLW FLW30 FLW FLW FLK FLK30 FLK FLK HRWR- high range water reducer, AEA- air entraining admixture

18 1. Terminology 2. Resources 3. Characterization 4. Strength efficiency 5. Durability efficiency - XF XF Durability: air void system in concrete Amount of 10% AEA solution [ml 0, ,35 0,3 0,25 0,2 0,15 0,1 0,05 0 CEM FLK FLW Series To otal air void conten [%] 8,00 7,00 20% CFBC fly ash 40% CFBC fly ash 6,00 CEM I 5,00 30% CFBC fly ash 4,00 3,00 CEM I + FLK 2,00 CEM I + FLW 1,00 0,00 0,0% 0,1% 0,2% 0,3% 0,4% 0,5% 0,6% 0,7% 0,8% 0,9% Content of the air entraining admixture [% of binder mass] Foam index test: the amount of the 10% water solution of the air-entraining admixture necessary to achieve the bubble stability Air void content in hardened concrete as a function of amount of air entraining admixture

19 1. Terminology 2. Resources 3. Characterization 4. Strength efficiency 5. Durability efficiency - XF XF Durability: air void system in concrete Air voids (white) in a polished section of concrete with different content of CFBC fly ash addition: left- 20% FLK, right- 40% FLW 0,25 Spacing factor of air voids 020 0,20 system versus the content of 0,15 fly ash from fluidized bed 0,10 hard coal combustion Linear traverse method using microscopic image analysis spa acing factor [m mm] 005 0,05 0,00 FLK FLW CFBC FA content [%]

20 1. Terminology 2. Resources 3. Characterization 4. Strength efficiency 5. Durability efficiency - XF XF Durability: freeze-thaw and deicing salt resistance mass of scaled material [kg/m2 2] rial ma ass of scaled mater [kg/m2] 2,5 2,0 15 1,5 1,0 0,5 0, number of F/T cycles 2,5 2,0 1,5 1,0 0,5 0, number of F/T cycles CEM I FLW20 FLW30 FLW40 CEM I FLK20 FLK30 FLK40 mass of scaled material S_56 [kg/ /m2] 2,5 2,0 1,5 1,0 after 56 cycles (Boras method) spacing factor [mm]: , , CFBC content [%] Mass of scaled material after cyclic freezing and thawing in 3% NaCl solution FLW FLK

21 1. Terminology 2. Resources 3. Characterization 4. Strength efficiency 5. Durability efficiency - XF XF Durability: volumetric freezethaw resistance section of local road made of 35 MPa concrete containing 20% CFBC FA Compressive strength th after cyclic freezing and thawing Co ompressive strength [MP Pa] mm cubes B A B A B Reference (B) A B After 160 F/T cycles (A) A mm cubes compress sive strength [M MPa] water storage 150 F/T cycles 51,7 52,1 50,2 49,7 lab concrete on site 0 CEM FLW20 FLW30 FLW40 er [ o C] direction of CFBC content increase --> temperature-time history inside the climatic 25 chamber temp. in chambe thermo 1 thermo :18 00:18 04:18 08:18 12:18 16:18 20:18 00:18 04:18 08:18 12:18 16:18 Time [hour:min]

22 1. Terminology 2. Resources 3. Characterization 4. Strength efficiency 5. Durability efficiency - XD XD Durability: chloride migration Non-steady state migration coefficient Tang/NordTest method NT Build 492 Concrete mixes at equal water content : days B0 - cement CEM I 360kg/m 3, water 162 l B15K and B30K 15% and 30% cement replacement by CFBC FA Katowice T15K and T30K 15% and 30% cement replacement by CFBC FA Turow superplasticizer i (variable content) t) natural gravel aggregate max.16mm

23 CONCLUSIONS 1. Potential to use of CFBC fly ash for partial replacement of cement up to 20%-30% in structural concrete together with WRA 2. At 20% replacement of cement by CFBC fly ash: increase of water/binder ratio by 9 % at equal slump Increase of long term compressive strength by 10-15% 15% the strength efficiency factor for CFBC fly ash was variable, although in average close to 1 3. Satisfactory air void system in concrete can be produced; decreased specific surface of voids and increased spacing factor 4. Freeze thaw durability adequate; frost salt scaling resistance decreased with increased CFBC fly ash and unburned carbon content 5. Air permeability coefficent kt (Torrent) increased (?) Non-steady state chloride migration coefficient decreased Thank you for your attention