Calcium Carbonate Fines or finely divided materials for
use in Concrete
NSSGA meeting
Caroline Talbot Ph.D., P.E., FACI
Overview
Potential Market Size
Where used and how
Barriers to entry in North America and Competition
What we have accomplished so far
DATA Performance
What else is needed
Cement Consumption by Market Segments
US Market Size Factors
• 112 millions tons of Cement used in concrete applications in 2007
• 136 million tons of Fly ash produced in the US 50 million tons used in concrete applications EPA Shortage due Solar, Wind, Natural Gas instead of Coal
• Aggregate gradation not always optimum Requires higher level of powder content
• Cement mills closing and not reopening due to new Environmental requirements on CO2 emissions Clinker imports…
• Green movement and LEED
Market segment potential in USA 2007 data
112 mil ton of cement = 450 mil yd3 of concrete
85% RM: 383 mil yd3
7% cement replacement: 35 lbs/yd3
Potential of 6.7 million tons of gcc
In this market it is hard to differentiate gcc vs dust fracture:
Residential market
DOT if we can be counted as cement
15% PC: 68 mil yd3
90% Wet Cast – 61.2mil yd3 10% Dry Cast – 6.8mil yd3
50-60 lbs/yd3 204000 tons of gcc
75% SCC - 46mil yd3
100 lbs/yd3 2.3 million tons of gcc
25% OC - 15 mil yd3
60 lbs/yd3 450000 tons of gcc
Grand total of 10 mil ton market size in 2007
North American Sales Potential PCA data
• Cement used in US 2007 (+ Canada ~ 15-20 Million) • 112 Million tons
• 7.5% replacement: 8.4 million tons + Canada
• That would include cements that includes CC interground, so not all would be for Producers
• Fly ash NA • Under pressure from EPA and Green Energy
• Quality and Availability ???
• 50 Million tons used in the construction market • If GCC takes 5% of that market: 2.5 Mil Tons
Active Clinker / Cement Production locations in the US
All Others
Ash Grove
Buzzi Unicem
Calportland
Essroc
GCC of America
Giant Cement Holding
Lehigh
Holcim
CEMEX
Lafarge
European Market vs. North America
Cement with inter-grinded limestone for >25 years • OPC 5% • Cem II A 6-20% (Lower performance than OPC and also <$) • Cem II B 21-35%
Use of fillers for >20 years • Mineral fillers standard exist since the 1990s • As fillers for aggregate gradation • As part of the cement (K factor since 2006? K25)
Canada has 5% inter-grinded limestone since early 80s • USA just approved few years ago
Canada just created a cement (GUL) with 15% inter-grinded limestone • Finer Blaine • Performance equal to GU and therefore same price • USA introduced also recently
GCC as a filler for aggregate is approved and in CSA and building code but no real guidance on how to design concrete using gcc. The US passed ASTM C 595, ASTM C1797 ACI 211N Proportioning with Limestone fillers
Europe vs North America
• Fillers: New specification exist in NA
• In Europe all considered similar and judged on performance under different exposures
• Fly Ash (in NA, FA is considered 100% cement)
• Slag is considered 100% cement
• Silica Fume is considered 100% cement
• CCF aggregate only
Classes of Concrete and exposure for Concrete
• Completely different in Europe vs. NA
• Data cannot be used
Cement category
Not the same
A few Market Cost figures
Fly Ash US: sells for 30-65 $/tons
• Recycle product
• EPA
• Availability
• Shortage price is going up
Canada: sells for 110-125 $/metric Tons • Distribution controlled by Cement Companies
Cement US: normally sells for 100-120$/T
• Expected to rise because of new environmental laws
• Cement shortage predicted in a few years
Canada: sells 140-160$/metric Tons
A few Market Cost figures
Slag US and Canada
• About same $/T than cement
• Recycle product
Silica Fume
• US and Canada
• 400 $/ton
Metakaolin
• US and Canada
• 200 $/ton
White Cement
• Double the price of Gray Cement
Barriers to Entry and Competition
• Lack of knowledge from Engineering community We need to educate and show how to use This Industry has not pushed into this part of the construction market
• Now we have ASTM Specification for a good/acceptable fillers for use in Concrete for Engineers /
Architect
• Now we ACI mix proportioning information available for our classes of concrete and exposure classes
• DOTs all have different requirements
• CO2 emission reduction versus cement What is the number to use LEED at this point this is not part of recycle content but when interground with cement it is a
LEED point qualifier?
Barriers to Entry and Competition Cont.
• Cement companies have worked together to develop data for their new cement meeting CO2 emission Equivalent performance to regular cement ASR Sulfates Durability Availability (swap with competition companies) Distribution
• Fly ash, Slag, Silica fume Availability (swap) Distribution Price Performance data (ASR, Durability)
• Availability of GCC throughout the US Perception is that there is not much available
• Silo availability at Producers sites
New Technology Introduction: Long term process This is standard for any new product in any Industry • TECH Data on new product use has to be available • ASTM specification C1797 • ACI document (USA) : to show how to use and design concrete using GCC ACI 211N • CSA approves (Canada) Thaumasite • Building code inclusion (both countries) • DOT and provinces codes • Education of potential users through trials mixes and papers published Within the companies wanting to enter the market, the 5 p’s:
Place: product available for distribution everywhere
Price: know cement, fly ash, slag pricing regionally (adjust pricing accordingly)
Product: relevant data for each segment (dry cast, Ready mix, precast (SCC and ordinary)
Promotion: marketing material (TDS, Brochure, table top etc…)
Personnel: trained for this market: this is a very high maintenance segment
What matters to concrete producers
Making money • Cost/yd3 cannot go up • Silo
Meeting Performance requirements
• Cement min and max W/C ratio • Strength • Slump • Set time • LEED points
Mix Design modifications
• Cementitious content • Water • W/C ratio max • Meet minimum strength • Meet workability • Setting time and finishing
What did the Industry in Europe do
Cement Cies have inter-grinded CC but lower perf. than OPC • Lower cost
Over the last 20 years • Worked with the different Research Groups • Develop data in a different Class of Concrete • Using CC with Interground cement as Performance Enhancer • Recently LC3 cements
Worked with the different Associations in place • Develop Specification (Ground CC production) • Acceptance for Use in different applications • Grout, SCC, Regular concrete • Aggregate gradation correction • Built laboratory for internal data development for potential customers • Have product available at a price that competes against cement Now • Use of GCC in concrete application is common • Can be counted as part of cement like fly ash • Application specific • More countries are looking at adopting it as cement replacement • Growing market • Green product, lower cost than OPC
What’s been accomplished so far
ASTM task group formed • as part C09.20 section 1 specification
ACI sub-commitee 211N: • Proportioning Concrete with Limestone Fillers • Part of ACI 211 Proportioning Concrete
Independent lab to develop data for SCC, regular concrete and dry cast but much more is needed Many presentations and research papers
• ICAR 108-1 • Koehler (PH.D thesis and papers) • Dust of fracture • Proportioning with mineral fillers
Talbot • ACI 237 session • Use limestone fillers in SCC • Calcima • SDC/Emerging technology session
NIST (D. Bentz) and Purdue University (Jason Weiss) and others like A. Radlinska
Data so far
Shows excellent performance (I can show the data) • Kamal Khayat in SCC
Lower HRWR demand Lower Skrinkage Faster form pressure decay Adequate durability (freeze-thaw, salt scaling, air void
analysis, RCP) Adequate strength development at 20% replacement Strength loss can be compensated by water reduction
• NRC showed identical performance to GUL Strength, Durability, Shrinkage
• In Dry-Cast good performance at 10% replacement
Does not need to be ground with cement Enhanced fly ash performance seems possible • Paper presented at TRB by NIST • FHWA is doing more tests
Offers to producers • Cost savings • Mix proportioning flexibility
Industry To Do List – Next 1-5 Years ASTM specification • Approved but not all DOT allows it AASHTO (controlled material versus Dust of fracture) ACI • A sub committee as part of 211 N LEED and CO2 emission: need to lobby the case for Green Concrete and cement reduction
Development with the help of Industry Expert of a table like Europe for mix design and clear directions on how to use as max content and %cement replacement in our class of concrete and exposure
Develop Data for regular concrete • Regular applications Case Studies • Sulfate attack • ASR • Dry Cast application: performance data and durability: • Other
Mineral fillers
Ground Product Sand production
Calcium carbonate Other mineralogy Manufactured Dust of fracture
Natural
We must look specifically at the mineralogy and physical properties of
each to evaluate how they will perform in concrete.
Mineral Filler: a finely divided mineral product at least 65% of which passes the U.S. Standard 75 μm (No. 200) sieve (ACI Concrete Terminology, terminology.concrete.org)
ACI Definition
Chemical and Physical Requirements
Parameter Type A Type B Type C
CaCO3, % ≥ 92 ≥ 70 NA
Sum of CaCO3+ MgCO3, % ≥ 95 ≥ 90 NA
Methylene blue value (mg/g) ≤ 3 ≤ 5 ≤ 5
Total Organic Content % ≤ 0.5 ≤ 0.5 ≤ 0.5
Particle size distribution, minimum % passing 300-µm (No. 50) sieve
150-µm (No.100) sieve
75- µm (No. 200) sieve
45- µm (No. 325) sieve
100
100
95
90
100
85
70
65
100
65
Strength Activity Index, % of control at 28d
see note 4
≥ 75 ≥ 75 ≥ 75
Water Requirement, maximum percent of control 120 120 120
Fineness (m2/kg), see note 5 ReportA ReportA ReportA
Moisture Content (%)B ≤ 1 ≤ 1 ≤ 1
A) The purchaser has the authority to approve a change in the fineness or to add a range if needed.
B) The moisture content is listed for materials that can be pneumatically transferred. If material is not pneumatically transferred,
then the purchaser can waive the moisture content requirement.
Where used
• Europe: Has been used in concrete applications for more than 25 years
• Interground
• OPC contains up to 5%,
• GRADE with 5-20%
• GRADE 20-35%
• As a Blend replacing a portion of cement to improve performance/Packing Density (cement-aggregate)
• Canada: CSA recently approved replacement up to 15% on clinker (interground)
• Cement companies mandated to reduce their CO2 emission
• Inter-grinding calcium carbonate with clinker
• If not interground
• At this point CSA says cannot be counted as cementitious
• Often used in formulated bagged products as a filler/cement replacement
Research Significance • US
• ASTM C1797 • Standard Specification for Ground Calcium Carbonate and Aggregate
Mineral Fillers for use in Hydraulic Cement Concrete • ASTM C 595 Blended cement • ASTM C1697 Standard specification for blended SCM • ACI 211 N: Proportioning with Limestone fillers
• Interground versus Blending
• Plenty of data available for use in SCC
• Needed a study to demonstrate performance in ordinary concrete
SCC results (Kamal Khayat)
SCC results (Kamal Khayat)
SCC results (Kamal Khayat)
SCC results (Kamal Khayat)
SCC results (Kamal Khayat)
• Two cement types: GU and GUL
• OMYA Limestone: Betocarb 3 µm and Betocarb 17 µm
Content in the concrete mixes: 7.5%-10%
• Concrete made with w/cm ratios : 0.35 to 0.70
Cementitious content : 250 kg/m3 to 420 kg/m3
For W/Cm = 0.35 series, same superplasticizer dosage (slump: 220 ± 20mm)
Concrete Mixes Parameters
Physical Properties of Cementitious
Properties Cement Limestone
GU GUL 3 µm 17 µm
Blaine fineness (m2/kg) 380 472
Specific Surface (m2/g) 2.92 3.31 5.04 1.26
Passing 45µm, % 97 99 100 96
Specific gravity 3.13 3.08 2.70 2.70
Compressive Strength
7 day 33.5 MPa 36.0 MPa
28 day 41.4 MPa 41.8 MPa
Concrete identification GU-CTL GUL-CTL
BC 3µ BC 17µ
10%
W/(P) 0.33 0.33 0.33 0.32
Cementitious
Composition (%)
Cement 100 100 90 90
Betocarb 0 0 10 10
Total binder (kg/m3) 420 420 420 420
Water (l/m3)* 150 150 150 145
Coarse aggregate (kg/m3) 1020 1020 1020 1020
Fine aggregate (kg/m3) 750 750 750 750
Air content- 60 min (%) 6.5 5.1 7.5 5.3
Unit weight (kg/m3) 2397 2425 2345 2430
Slump (mm)-10 min/60 min 210/155 205/95 235/185 240/130
Composition and Properties of Fresh Concrete (1)
* 4.5 L/m3 of superplasticizer for this series of concrete mixtures
Concrete Type
W/Cm
Durability Factor (%)
Freeze/Thaw
Compressive Strength, MPa
Chloride-ion Penetration,
Coulombs >300 cycles 1d 28d 28d 91d
GU-CTL 0.33 100 34.2 56.8 2458 1558
GUL-CTL 0.33 100 34.0 56.0 2461 1804
BC 3µ 10% 0.33 100 31.7 55.7 2609 1597
BC 17µ 10% 0.32 100 31.3 54.4 2864 1659
Properties of Hardened Concrete (1)
Conclusion • Results show good performance overall as a Blend or
Interground (similar results)
• When added separately • Potential savings • Flexibility of mix design
• Addition rate • Micron size
• Slump retention
• France allows use as partial replacement of cement • For grade smaller than cement • From sources that are controlling
• PSD • Chemistry • Produced in continuous
Study conducted at NIST (D Bentz)
Study conducted at NIST (D Bentz)
Conclusions
•Fine limestone powder additions accelerate setting times of high-volume fly ash (Class
C and Class F) mixtures, even as a delayed addition
•Finer limestone and greater quantities of limestone have a greater acceleration effect
•Even though anatase also has a very small particle size, it does not greatly accelerate
setting times
–This indicates that the limestone likely has both chemical and physical effects at early
ages
•A desired setting time can be engineered by altering the particle size and/or percentage
of the limestone powder by taking advantage of the linear relationship between limestone
surface area and setting time reductions
Study conducted at NIST (D Bentz)
This study focused on mitigating setting time delays via the addition of fine limestone
powders. Other properties that should be investigated include:
–Compressive strength development
•Likely increased by about 10 % at 1 d, less later
–Autogenous shrinkage at early ages
•These results indicate a promising potential for ternary mixtures to achieve equivalent
setting performance to 100% cement systems with substantial cost, energy, and CO2
footprint reductions, successfully achieving both constructability and sustainability.
Study conducted at NIST (D Bentz)
Role of limestone in greater hydration efficiency
(Tim Cost, HOLCIM)
Limestone is not inert, but contributes to hydration both physically and chemically.
Physical mechanisms:
Enhanced particle packing and paste density due to enhanced PSD
“Nucleation site” phenomenon – limestone particles between clinker grains become intermediate sites for CSH
crystal growth
Chemical mechanisms:
Limestone contributes calcium compounds that go into solution and become available for hydration interaction
Calcium carbonate reacts with aluminate compounds to produce durable mono-and hemi-carboaluminate hydrate
crystals
– De Weerdt , Kjellsen, Sellevold, and Justnes, “Synergy Between Fly Ash and Limestone Powder in Ternary Cements,” Cement and Concrete Composites, Vol. 33, Issue
1, January 2011, pp 30-38.
Synergistic strength benefits are, in large part, the
result of documented CaCO3 interaction w/ aluminates
and formation of carboaluminate crystals
(Tim Cost, HOLCIM)
How fine should PLC be ground?
Example fineness trends, PLC vs. clinker and limestone component fractions
(Tim Cost, HOLCIM)
Fineness of the grind is typically used to “tune” 28-day strength to equal that of OPC in C109
mortar and/or simple concrete mixtures (mild or no SCM use)
Benefits of synergies with SCMs become increasingly significant with higher fineness and
higher SCM replacement of cement
Practical limits of increased fineness benefits vary for each plant
How fine should PLC be ground?
(Tim Cost, HOLCIM)
Observed trends suggest that equivalent performance should be
possible with at least 10% higher fly ash replacement, using PLC.
(Tim Cost, HOLCIM)