Presentation on theme: "Increased Limestone Mineral in Cement the Effect on Chloride Ion Ingress of Concrete – A Literature Review B T (Tom) Benn – Adelaide Brighton Cement Ltd."— Presentation transcript:
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 IntroductionBackground to mineral additionsCementsLimestoneCement kiln dustSupplementary cementitious materialsGeneral properties of concreteDurabilityChloride ingressTransport mechanismsConclusions & Research proposal
3 Mineral Additions & Chloride Ingress IntroductionLimestone addition first used 1965Heidelberg cement at 20%5% mineral additionEurope in general early 1980’sSouth Africa 1982Canada 1983Australia 1991USA 2005Limestone cements (>5%) 1992 in ENV 197-1
5 Mineral Additions & Chloride Ingress LimestoneAustralia & EuropeNatural inorganic mineral materialCaO3 not less than 75% by massIf 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 massCaO3 content 80 % or greater no additional testingCanadaCaO3 content at least 70% by massUSACaO3 content at least 75% by mass
6 Mineral Additions & Chloride Ingress Cement Kiln DustDust created and extracted from kilnAlso known as by-pass dustTypically between 7% – 15% of clinkerWhy removedCauses build up and rings in kiln and preheaterCauses abnormal setting and strength characteristics in cementIf high in chlorides contributes to reinforcement corrosionIf high in alkalis contributes to ASR reactionChemistrySimilar to raw materials for cement and clinker
8 Mineral Additions & Chloride Ingress Supplementary Cementitious MaterialsFly ash, ground granulated blastfurnace slag, silica fumeAdvantages of usingImproved workabilityBetter cohesiveness and pumpabilityImproved post 28-day strengthsReduction in ASR with reactive aggregatesReduced shrinkage (fly ash)Reduced heat of hydrationLower permeability (important for resistance to chloride ingress)Improved resistance to chemical (sulphate) attackProtection of steel in marine environments (GGBS)
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 literatureVoglis et al. (2005) - for similar compressive strength in concretelimestone cement required a wider particle size distributionTsivilis 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 strengthdue to formation of nucleation sitesVogilis et al. (2005) - increased early hydration and strengthdueto the early formation of calcium carboaluminates.
14 Mineral Additions & Chloride Ingress Findings on properties in the literatureMatthews (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 reducedHooton, 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 DurabilityDurability 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 mechanismsDiffusion – 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 literatureEffect of limestone additions on the “chloride permeability’ of concrete (Tsivilis et al. 2000)
19 Mineral Additions & Chloride Ingress Findings reported in international literatureEffect of Limestone Additions on Chloride Penetration of Concrete – Oxygen Permeability (Matthews, 1994)
20 Mineral Additions & Chloride Ingress Findings reported in international literatureEffect 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 ConclusionsSome 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 researchMortar with w/c ratio ≈ 0.45 with following cementitious contents:Control - cement only mix, limestone additions = 5%, no CKDExperimental 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 findingsResearch will support sustainability as suggested by the Kevin Gluskie