The E ff ect of In-Situ Development of Nano-calcium Carbonate on - - PowerPoint PPT Presentation

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The Effect of In-Situ Development of Nano-calcium Carbonate on Industrial Concrete

Sean Monkman, VP Technology Development CarbonCure Technologies Mark MacDonald, Director of Research CarbonCure Technologies Paul Kenward Greg Dipple University of British Columbia, Department of Earth, Ocean and Atmospheric Sciences

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Carbonation Of Freshly Hydrating Cement

Dissolution

(Ca2+ Supply)

C3S(alite) + 3H2O ↔ 3Ca2+ + SiO2

0 + 6OH-

C2S(belite) + 2H2O ↔ 2Ca2+ + SiO2

0 + 4OH-

Ca(OH)2 + H2O ↔ Ca2+ + 2OH- + H2O

Precipitation

(CO2 Storage)

Ca+2

(aq) + CO3

• 2

(aq) ↔ CaCO3 (s)

=

CO2 Dissociation

(CO3

• 2 Supply)

CO2 (g) ↔ CO2 (aq) CO2 (aq) + H2O ↔ H2CO3 (aq) H2CO3 (aq) ↔ HCO3

• (aq) + H+

HCO3

• (aq) ↔ CO3
• 2 (aq) + H+

+

Seeking beneficial reuse of CO2 in concrete production

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Industrial Masonry Pilot

• Dosed 1.5% CO2 by

weight of cement

• Added CO2 as part of

normal batching and mixing

• Monitored strength,

density and absorption

• Quantified CO2 uptake

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Industrial trial

CMU Compressive Strength

7 day 28 day 56 day 62% 118% 68% 119% 76% 119% 1000 2000 3000 4000 5000 Blended Control 1.5% CO2 1.5% CO2 + water Compressive Strength (psi) Condition

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Industrial trial

CMU Absorption and Density

130.7 124.1 130.4 122 124 126 128 130 132 134 Control 1.5% CO2 1.5% CO2 + water Density (lb/ft3) Condition 8.5 7.5 7.0 6.0 6.5 7.0 7.5 8.0 8.5 9.0 9.5 Control 1.5% CO2 1.5% CO2 + water Absorption (ln/ft3) Condition

• Carbonated: 5.0% lower density, 11% lower absorption
• Carbonated w/ water increase: 0.2% lower density, 18% lower absorption

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Industrial trial

Masonry Takeaways

• Carbonated batch had

drier appearance and poor compaction

• Increased water by 14%,

product appearance was unchanged

• At target density a

strength benefit of about 18% was realized

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Ready mixed concrete trial

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• CO2 was supplied into truck

after batching.

• Monitored slump,

temperature, compressive strength, air content

• The concrete dosed with CO2

20-25 min after the mixing started.

• Targeted constant water

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Industrial Trial

Fresh Results

• Workability was decreased due to CO2
• Air content may have decreased with higher

dose of CO2

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Mix Air Content Slump (in) Temperature (°C) CO2 Uptake Control 5.9% 7 25.8

• 1.0% CO2

5.9% 4 28.1 0.44% 1.5% CO2 4.5% 3 28.6 1.69%

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Industrial Trial

Compressive Strength Results

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Control 0.44% CO2 1.69% CO2 96% 104% 107% 103% 98% 109% 117% 111% 1000 2000 3000 4000 5000 5 10 15 20 25 30 35 40 1 day 7 days 28 days 56 days Compressive strength (psi) Compressive Strength (MPa) Test Age

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Ready-mix takeaways

• Workability reduced
• Strength neutral or

improved

• Resistivity unaffected
• Durability assessment
• ngoing

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What did the CO2 do?

11 20 40 60 80 100 120 140 2000 2100 2200 2300 2400 2500 Slump (mm) Mix water (ml) Control CO2 dose 1 CO2 dose 2 98.1% ¡ 97.6% ¡ 95.7% ¡

1.88 1.90 1.92 1.94 1.96 1.98 2.00 2.02 2.04 2.06 2.08 2.10 Control CO2 dose 1 CO2 dose 2 CO2 dose 3 Cylinder Density (g/cm3) Condition

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Mechanism

• Carbon dioxide addition leads to nano-CaCO3

formation.

• Compaction and workability effects were

attributable to new surface area created

• Strength benefit associated with nucleation
• Study ongoing to characterize the reaction
• Effects observed when seeking to maximize CO2

uptake.

• In ready mix, optimizing the dose to achieve

property benefits can avoid the workability loss.

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Model Comparison to SCMs

10000 20000 30000 40000 50000 60000 70000 80000 90000 100000 Ground Slag Fly Ash Calcined Shale Calcined Clay Metakaolin Silica Fume 50 nm CaCO3 25nm CaCO3 Specific Surface Area (m2/kg) 14

In situ formed nano-CaCO3 has far greater a specific surface area than SCMS.

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Comparison to Silica fume

Component Unit Block Trial RM trial CO2 uptake % bwc 1.40% 1.69% Amount CaCO3 kg 10.60 12.91 Particle diameter nm 25 25 New surface area m2 625,331 761,665 SF specific surface area m2/kg 20,000 20,000 Amount silica fume % bwc 9.39% 11.33%

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Model

• Surface bound rhombohedral particle
• Small amounts of CO2 = large amounts of silica fume
• A particle of 25 nm is likely a conservatively large estimate

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In situ nano-CaCO3 formation

• Simple retrofit technology
• No dispersion/sonication required
• Cement sensitivity, as per admixtures
• Widely available feedstock, uses waste CO2

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Thank You

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IMG_1619.JPG Thank You

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