Concrete Technology - Quarry：混凝土技术的采石场

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 AustraliaMineral Additions & Chloride IngressIntroductionBack

2、ground to mineral additionsCementsLimestoneCement kiln dustSupplementary cementitious materialsGeneral properties of concreteDurabilityChloride ingressTransport mechanisms Conclusions & Research proposalMineral Additions & Chloride IngressIntroductionLimestone addition first used 1965Heidelberg ceme

3、nt at 20%5% mineral additionEurope in general early 1980sSouth Africa 1982Canada 1983Australia 1991USA 2005 Limestone cements (5%) 1992 in ENV 197-1Mineral Additions & Chloride IngressComparison of cement properties PropertyUnitsType GPCEM I 32.5CEM I 42.5Type IStandardAS 3972EN 197-1EN 197-1ASTM C1

4、50Initial setMinutes 45 75 75 45Final setHours 6- 6.25MgO% 4.5 (clinker) 5.0 5.0 6.0Chloride ion % 0.10 0.10 0.10-SO3%3.5 3.5 3.5 3.0 (C3A 8%)Loss on ignition%- 5.0 5.0 3.0Strength 2-dayMPa- 10.0-Strength 3-dayMPa-12.0 (cubes)Strength 7-dayMPa 35 16.0-19.0Strength 28-dayMPa 45 32.5 52.5 42.5 62.528.

5、0Mineral Additions & Chloride IngressLimestoneAustralia & EuropeNatural inorganic mineral materialCaO3 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 massCaO3 content 80 % or greater

6、 no additional testing CanadaCaO3 content at least 70% by massUSACaO3 content at least 75% by massMineral Additions & Chloride IngressCement 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 preh

7、eaterCauses 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 Mineral Additions & Chloride IngressCement kiln dust chemistryConstitue

8、ntLong dry kilns (U.S. EPA (1993)ABC data (07 10)Silicon dioxide4.3 10.19.5 20.6Aluminium oxide1.0 3.32.8 4.5Iron oxide0.7 2.31.8 3.1Calcium oxide11.0 45.041.5 62.9Magnesium oxide0.4 2.00.8 1.6Sulphur trioxide0.1 7.70.5 4.7Chlorine0.08 2.70.6 7.5Potassium oxide0.2 9.71.8 15.5Sodium oxide0.07 1.120.2

9、 1.1Mineral Additions & Chloride IngressSupplementary 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

10、 ash)Reduced heat of hydrationLower permeability (important for resistance to chloride ingress)Improved resistance to chemical (sulphate) attackProtection of steel in marine environments (GGBS)Mineral Additions & Chloride IngressMineral Additions & Chloride IngressCompressive strengths of various gr

11、ades of lab concrete (Benn & Thomas 2012)Mineral Additions & Chloride IngressSet times of various grades of lab concrete (Benn & Thomas 2012)Mineral Additions & Chloride IngressDrying shrinkage of various grades of lab concrete (Benn & Thomas 2012)Mineral Additions & Chloride IngressFindings on prop

12、erties in the literatureVoglis 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

13、 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.Mineral Additions & Chlori

14、de IngressFindings 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 reduced

15、 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.Mineral Additions & Chlo

16、ride IngressDurabilityDurability 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

17、ingress to prevent corrosion of reinforcement,Having a classical faade that does not seem to age with changes in architectural fashions.Mineral Additions & Chloride IngressDescription of ingress mechanismsDiffusion transfer free ions in the pore solution from high concentration to low concentration

18、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 dra

19、wn 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.Mineral Additions & Chloride IngressMechanism of chloride transport (CCAA 2009)Miner

20、al Additions & Chloride IngressFindings reported in international literatureEffect of limestone additions on the “chloride permeability of concrete (Tsivilis et al. 2000) Mineral Additions & Chloride IngressFindings reported in international literatureEffect of Limestone Additions on Chloride Penetr

21、ation of Concrete Oxygen Permeability (Matthews, 1994)Mineral Additions & Chloride IngressFindings reported in international literatureEffect of Limestone Addition on the Chloride Diffusion Coefficient of Concrete by Initial Surface Absorption (Dhir et al. 2007)Mineral Additions & Chloride IngressFi

22、ndings reported in international literatureMineral Additions & Chloride IngressConclusionsSome 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 mine

23、ral 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