1. Increased Limestone Mineral in Cement the Effect on Chloride Ion Ingress of Concrete – A Literature Review B T (Tom) Benn – Adelaide Brighton Cement Ltd Ass Prof Daksh Baweja – University of Technology Sydney Prof Julie E Mills – University of South Australia

2. Mineral Additions & Chloride Ingress
Introduction
Background to mineral additions
Cements
Limestone
Cement kiln dust
Supplementary cementitious materials
General properties of concrete
Durability
Chloride ingress
Transport mechanisms
Conclusions & Research proposal

3. Mineral Additions & Chloride Ingress
Introduction
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

4. Mineral Additions & Chloride Ingress
Comparison of cement properties
Property
Units
Type GP
CEM I – 32.5
CEM I – 42.5
Type I
Standard
AS 3972
EN 197-1
ASTM C150
Initial set
Minutes
≥ 45
≥ 75
Final set
Hours
< 6 --
≤ 6.25
MgO %
< 4.5
(clinker)
≤ 5.0
≤ 6.0
Chloride ion
≤ 0.10
SO3
≤3.5
≤ 3.5
≤ 3.0 (C3A < 8%)
≤ 3.5 (C3A > 8%)
Loss on ignition
≤ 3.0
Strength 2-day
MPa
≥ 10.0
Strength 3-day
12.0 (cubes)
Strength 7-day
≥ 35
≥ 16.0
19.0
Strength 28-day
≥ 32.5 ≤ 52.5
≥ 42.5 ≤ 62.5
28.0

5. 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

6. Mineral Additions & Chloride Ingress
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

7. Mineral Additions & Chloride Ingress
Cement 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

8. Mineral Additions & Chloride Ingress
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)

9. Mineral Additions & Chloride Ingress

10. Mineral Additions & Chloride Ingress
Compressive strengths of various grades of lab concrete (Benn & Thomas 2012)

11. Mineral Additions & Chloride Ingress
Set times of various grades of lab concrete (Benn & Thomas 2012)

12. Mineral Additions & Chloride Ingress
Drying shrinkage of various grades of lab concrete (Benn & Thomas 2012)

13. Mineral Additions & Chloride Ingress
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.

14. Mineral Additions & Chloride Ingress
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’.

15. Mineral Additions & Chloride Ingress
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.

16. Mineral Additions & Chloride Ingress
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.

17. Mineral Additions & Chloride Ingress
Mechanism of chloride transport (CCAA 2009)

18. Mineral Additions & Chloride Ingress
Findings reported in international literature
Effect of limestone additions on the “chloride permeability’ of concrete (Tsivilis et al. 2000)

19. Mineral Additions & Chloride Ingress
Findings reported in international literature
Effect of Limestone Additions on Chloride Penetration of Concrete – Oxygen Permeability (Matthews, 1994)

20. Mineral Additions & Chloride Ingress
Findings reported in international literature
Effect of Limestone Addition on the Chloride Diffusion Coefficient of Concrete by Initial Surface Absorption
(Dhir et al. 2007)

21. Mineral Additions & Chloride Ingress
Findings reported in international literature

22. Mineral Additions & Chloride Ingress
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.

23. Mineral Additions & Chloride Ingress
Proposed research
Mortar 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