mineral additions & chloride ingress

CMIC 2012

Increased Limestone Mineral in Cement the Effect on Chloride Ion Ingress of

Concrete – A Literature Review

B T (Tom) Benn – Adelaide Brighton Cement LtdAss Prof Daksh Baweja – University of Technology Sydney

Prof Julie E Mills – University of South Australia

CMIC 2012

Mineral Additions & Chloride IngressIntroduction

• Background to mineral additions• Cements• Limestone• Cement kiln dust• Supplementary cementitious materials• General properties of concrete• Durability• Chloride ingress

• Transport mechanisms

• Conclusions & Research proposal

CMIC 2012

Mineral Additions & Chloride IngressIntroduction

• Limestone addition first used 1965• Heidelberg cement at 20%

• 5% mineral addition• Europe in general early 1980’s• South Africa 1982• Canada 1983• Australia 1991• USA 2005

• Limestone cements (>5%) 1992 in ENV 197-1

CMIC 2012

Mineral Additions & Chloride IngressComparison of cement properties

Property Units Type GP CEM I – 32.5 CEM I – 42.5 Type I

Standard AS 3972 EN 197-1 EN 197-1 ASTM C150

Initial set Minutes ≥ 45 ≥ 75 ≥ 75 ≥ 45

Final set Hours < 6 -- -- ≤ 6.25

MgO % < 4.5 (clinker)

≤ 5.0 ≤ 5.0 ≤ 6.0

Chloride ion % ≤ 0.10 ≤ 0.10 ≤ 0.10 --

SO3 % ≤3.5 ≤ 3.5 ≤ 3.5 ≤ 3.0 (C3A < 8%)≤ 3.5 (C3A > 8%)

Loss on ignition % -- ≤ 5.0 ≤ 5.0 ≤ 3.0

Strength 2-day MPa -- -- ≥ 10.0 --

Strength 3-day MPa -- -- -- 12.0 (cubes)

Strength 7-day MPa ≥ 35 ≥ 16.0 -- 19.0

Strength 28-day MPa ≥ 45 ≥ 32.5 ≤ 52.5 ≥ 42.5 ≤ 62.5 28.0

CMIC 2012

Mineral Additions & Chloride Ingress

Limestone• Australia & Europe

• Natural inorganic mineral material

• CaO3 not less than 75% by mass

• If CaO3 between 75% & 80% must be tested:

• Clay content must be less than 1.20% (methylene blue test)• Total organic test not greater 0.50% by mass

• CaO3 content 80 % or greater no additional testing

• Canada• CaO3 content at least 70% by mass

• USA• CaO3 content at least 75% by mass

CMIC 2012


Cement Kiln Dust• Dust created and extracted from kiln

• Also known as by-pass dust• Typically between 7% – 15% of clinker

• Why removed• Causes build up and rings in kiln and preheater• Causes abnormal setting and strength characteristics in cement• If high in chlorides contributes to reinforcement corrosion• If high in alkalis contributes to ASR reaction

• Chemistry• Similar to raw materials for cement and clinker

CMIC 2012

Mineral Additions & Chloride IngressCement kiln dust chemistry

Constituent Long dry kilns (U.S. EPA (1993) ABC data (07 – 10)

Silicon dioxide 4.3 – 10.1 9.5 – 20.6

Aluminium oxide 1.0 – 3.3 2.8 – 4.5

Iron oxide 0.7 – 2.3 1.8 – 3.1

Calcium oxide 11.0 – 45.0 41.5 – 62.9

Magnesium oxide 0.4 – 2.0 0.8 – 1.6

Sulphur trioxide 0.1 – 7.7 0.5 – 4.7

Chlorine 0.08 – 2.7 0.6 – 7.5

Potassium oxide 0.2 – 9.7 1.8 – 15.5

Sodium oxide 0.07 – 1.12 0.2 – 1.1

CMIC 2012


Supplementary Cementitious Materials• Fly ash, ground granulated blastfurnace slag, silica fume• Advantages of using

• Improved workability• Better cohesiveness and pumpability• Improved post 28-day strengths• Reduction in ASR with reactive aggregates• Reduced shrinkage (fly ash)• Reduced heat of hydration• Lower permeability (important for resistance to chloride ingress)• Improved resistance to chemical (sulphate) attack• Protection of steel in marine environments (GGBS)

CMIC 2012


Strength of concrete Made with Portland Cement & Portland limestone cement

(from Hooton & Thomas 2010)

No Water Reducing Admixture With Water Reducing Admixture

PC-1 PLC-2 PC-2 PLC-4 PC-1 PLC-1 PLC-2 PLC-3 PC-2 PLC-4

Limestone, % 4.8 12 4.8 12 4.8 12 12 12 4.8 12

Blaine, m2/kg 380 500 380 500 380 450 500 580 380 500

w/c ratio 0.505 0.512 0.505 0.518 0.491 0.498 0.498 0.508 0.495 0.502

Slump, mm 115 110 115 110 110 110 110 80 105 105

1-day 19.2 21.4 18.5 18.9 21.8 21.9 23.6 24.6 21.0 22.0

7-day 33.5 32.7 32.3 31.6 35.3 34.4 35.2 36.7 35.6 35.0

28-day 41.1 39.8 39.3 39.9 42.2 40.3 41.9 42.5 42.3 41.5

56-day 43.8 43.3 44.0 43.0 45.2 43.6 44.7 46.6 45.2 45.8

CMIC 2012


Compressive strengths of various grades of lab concrete (Benn & Thomas 2012)

CMIC 2012


Set times of various grades of lab concrete (Benn & Thomas 2012)

CMIC 2012


Drying shrinkage of various grades of lab concrete (Benn & Thomas 2012)

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Findings on properties in the literature• Voglis et al. (2005) - for similar compressive strength in concrete• limestone cement required a wider particle size distribution

• Tsivilis et al. (1999a) – increasing tricalcium aluminate (C3A)

• and reducing the tricalcium silicate (C3S)

• increases compressive strength at all ages irrespective of the limestone between 10% and 35%.

• Bonavetti et al. (2003) - the increased early hydration and strength • due to formation of nucleation sites • Vogilis et al. (2005) - increased early hydration and strength • dueto the early formation of calcium carboaluminates.

CMIC 2012


Findings on properties in the literature• Matthews (1994) - for the same slump • (w/c) ratio needs to increase by 0.01 for limestone up to 5% • a further 0.01 when increased from 5% to 25%. • Schmidt (1993) - using cement from a different source,

reported water demand for concrete could be reduced

• Hooton, Nokken & Thomas (2007) supported the statement by Tsivilis et al. (1999a) ‘… that the appropriate choice of clinker quality, limestone quality, percentage limestone content and cement fineness can lead to the production of a limestone cement with the desired properties’.

CMIC 2012


Durability• Durability can be different things to different people such as:

• Not having to repair a structure for 20 years or more,• Able to cope with changes in use,• Able to cope with changes in loading,• Able to resist chemical attack e.g. acids, alkali-silica reaction,• Able to prevent chloride ingress to prevent corrosion of

reinforcement,• Having a classical façade that does not seem to age with changes

in architectural fashions.

CMIC 2012


Description of ingress mechanisms• Diffusion – transfer free ions in the pore solution from high

concentration to low concentration regions.• Capillary absorption – when moisture encounters the dry surface of

the concrete, it will be drawn into the pores by capillary suction, this often happens with wetting and drying cycles.

• Evaporative transport (also called wicking) – similar to absorption but where moisture, containing ions, is drawn from the wet surface through the matrix to the dry surface.

• Hydrostatic pressure or permeation – where the hydraulic pressure on one side of the concrete forces the liquid, containing ions, into the concrete matrix.

CMIC 2012


Mechanism of chloride transport (CCAA 2009)

Exposure Type of structure Primary chloride transport mode

Submerged Substructure below low tide Diffusion

Basement exterior walls or transport tunnel liners below low tide. Liquid containing structures

Permeation, diffusion and possibility wick action

Tidal Substructures and superstructures in tidal one.

Capillary absorption and diffusion

Splash and

spray

Superstructures about high tide in the open sea.

Capillary absorption and diffusion (also carbonation)

Coastal Land based structures in coastal area or superstructures above high tide in river estuary or body of water in coastal area.

Capillary absorption (also carbonation)

CMIC 2012


Findings reported in international literature

Effect of limestone additions on the “chloride permeability’ of concrete (Tsivilis et al. 2000)

Property Percentage limestone

0 10 15 20 35

Fineness (m2/kg) 260 340 366 470 530

Mortar: 28 day strength (MPa) 51.1 47.9 48.5 48.1 32.9

Concrete w/c 0.70 0.62

Concrete: 28 day strength (MPa) 31.9 27.4 27.3 28.0 26.6

Concrete: RCPT (Coulombs) 6100 5800 6000 6400 6600

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Mineral Additions & Chloride IngressFindings reported in international literature

Effect of Limestone Additions on Chloride Penetration of Concrete – Oxygen Permeability (Matthews, 1994)

CMIC 2012


Findings reported in international literature

Effect of Limestone Addition on the Chloride Diffusion Coefficient of Concrete by Initial Surface Absorption

(Dhir et al. 2007)

CMIC 2012

Mineral Additions & Chloride IngressFindings reported in international literature

Diffusion coefficients (x 10-12 m2/s) for concrete after 35 days immersion in 3% NaCl solution (Hooton, Ramezanianpour & Schutz, 2010)

GU 100%

PLC10 100%

PLC15 100%

GU 70% GGBS 30%

PLC10 70% GGBS 30%

PLC15 70% GGBS 30%

Cs (% mass) 0.73 0.84 0.8 1.1 1.07 0.98

Da (m2/s*10-

12)

15.9 15.6 22.5 8.07 6.11 8.25 Notes:

(i) GU is general use Portland cement. (ii) PLC is Portland limestone cement with either 10% or 15 % limestone. (iii) The 70% implies 70 % cement and 30 % slag.

CMIC 2012


Conclusions• Some indication that without the inclusion of SCM the durability may

be at risk (Irassar et al. 2001). • Literature supports the hypothesis that that the use of SCM will

improve the durability even with high mineral additions(Thomas & Hooton 2010)

• Previous research indicates that CKD can be added to cement (Daugherty and Funnell 1983).

• Gap in the data as no reference has been found relating to chloride ingress where CKD is added during the milling of the clinker and in particular where the CKD contains chlorides.

• Gap in the knowledge on the effect of the inclusion of both higher limestone additions and CKD in cement on the chloride ingress into concrete, made with and without fly ash or slag.

CMIC 2012


Proposed researchMortar with w/c ratio ≈ 0.45 with following cementitious contents:

• Control - cement only mix, limestone additions = 5%, no CKD• Experimental cement mixes, limestone additions = 10% & 15% + CKD.• Cement/fly ash mixes, fly ash replacement = 20% & 30%.• Cement/slag mixes, slag replacement = 30% and 50%.• Measure compressive strengths development for up to three years.• Measure chloride diffusion for up to three years (Nord Test NT 443 ?)• Measure rapid chloride permeability (RCPT ASTM C 1202 ?)

Concrete with f’C of 40 MPa to confirm mortar findings

Research will support sustainability as suggested by the Kevin Gluskie

mineral additions & chloride ingress

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