Mineral Additions & Chloride Ingress

1. Increased Limestone Mineral in Cement the Effect on Chloride Ion Ingress of Concrete – A Literature ReviewB T (Tom) Benn – Adelaide Brighton Cement LtdAss Prof Daksh Baweja – University of Technology SydneyProf 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

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

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