Durability, Concrete, Environment and Sustainability in the Eurocodes

Transcription

1 Durability, Concrete, Environment and Sustainability in the Eurocodes Steinar Leivestad Standard Norge

2 Norwegian clients asks for environmentalfriendly concrete in 70 80% of all new contracts voluntarily Zero-emission building in Trondheim 2

3 Norwegian Concrete - the past and - the future We have great expectations to the general applicability of the Eurocodes

4 Development of the concrete-material Prime drivers; Sutainability Environmental- and CO 2 - footprint New cements and new binder combinations Utilize gain in strength from 28- to 91-days Re-use of aggregates Other??? Consequences with respect to Durability Strength and strength development Mechanical properties in design There are two perspectives To save the world (+ 2 0 C) To save the concrete (by maintaining its competitive position) Reduced concrete volume for same function Less CO 2 per m 3 used Account made up after end of life-cycle 4

5 Development on the material side will normally lead to changes in performance, the requirements must be able to accommodate this in an effective way With todays «Deemed to Satisfy» (DtS) will new materials have to be documented to show «equivalence» based on a material (CEM I) that is expected not to remain available in the future, and which show large variations in performance even within the same class With performance based design we have a discipline that is not yet mattured enough for daily use, where the selection of parameters gives much room for «optimistic» and «pessimistic» choices with large variations in results. The parameters should therefore be made on a neutral basis as part of the standardization. By use of «Exposure Resistance Classes» (ERC) we can have a performance based definition of classes, and the standards can give a calibrated set of requirements to; Exposure Class / Exposure Resistance Class / cover to reinforcement dependant of Design Working Life. 5

6 Material resistance classes The Ganeral provisions applies Durability Design of concrete structures Provisions coordinated between the various standards Interface Society / construction project Societal expectations + National legislation Eurocode Basis of structural design TC250 Basic requirement Eurocode Actions on structures TC250/SC1 Eurocode Design of concrete structures TC250/SC2 Design provisions EN Execution of concrete structures TC104/SC2 Ececution requirements EN Concrete TC104/SC1 ISO 6934 or ETA Tendons & PT kits EN reinforcement EN xx or ETA Prefabricated elements TC229 Product and testing standards TC104/SCs and WGs Product and testing standards Product and testing standards Product and testing standards

7 Meetings of TC250/SC2 and TC104/SC1 dealing with Durability and the work of the JWG TC250/SC2 TC104/SC1 or TC104 2/ Larnaca (20) Mentioned Brussels (23) Mentioned 17-18/ Helsinki (24) Discussed 13-14/ Stockholm (21) Pre mature, established TG / Brussels (25) Resolution / Berlin (22) Discussed Resolution / Torino (26) Discussed 7-8/ Budapest (27) Discussed 16-17/ Gent (23) Discussed Resolution / London (28) Discussed 07-08/ Madrid (29) Discussed 15-16/2010 Delft (24) No discussion Presentation TC104 30/ Oslo (30) Presentation Helsinki (25) No discussion 12-13/ Milan (31) Principles 23-24/ Milan (26) Principle agreed agreed 28-29/ Brussel (32) Discussed Berlin (27) No discussion 01/ Berlin (33) Discussed 20-21/ Paris (28) Discussed 19/ Ispra (34) Principles agreed 5-6/ Vienna (29) Discussed 22-23/ Workshop in Brussels convened by JWG 04/ Berlin (35) Discussed 5-6/ Brussels (30) Discussed Resolution 440 agreed 05/ Berlin (36) Reported Berlin (37) Reported 10-11/ London (31) SC1/WG1 Road map discussed Zürich (38) Reported The work on durability and the development of the concept by the JWG has been thorougly presented and discussed in TC250/SC2 and TC104/SC1since

8 Eurocode 2 Section 4 NDPs (5) The minimum cover values for reinforcement and prestressing tendons in normal weight concrete taking account of the exposure classes and the structural classes is given by cmin,dur. Note: Structural classification and values of c min,dur for use in a Country may be found in its National Annex. The recommended Structural Class (design working life of 50 years) is S4 for the indicative concrete strengths given in Annex E and the recommended modifications to the structural class is given in Table 4.3N. The recommended minimum Structural Class is S1. The recommended values of c min,dur are given in Table 4.4N (reinforcing steel) and Table 4.5N (prestressing steel). Cover Table 4.3N - 4.5N out of 27; 7 use recommended value 5 use recommended value with conditions 15 use ammended values Systematic review 30 comments 8

9 Exposure resistance classes system and definitions System Corrosion of reinforcement Deterioration of concrete Carbonation Resistance Class Low Medium Chloride Resistance Freeze/thaw Resistance Chemical Aggressiveness Class Class Class High Medium High Medium High High Low Medium Definitions Corrosion of reinforcement Deterioration of concrete Carbonation Resistance Class RXC RXC RXC Chloride Resistance Class RXSD RXSD RXSD Freeze/thaw Resistance Class RXF RXF Chemical Aggressiveness Class (for later) RXCA RXCA (Low) (Medi- (High) (Low) (Medi- (High) (Medium) (High) (Medium) (High) um) um) Void, not mature Definition of class is 50- Definition of class is 50- Definition of class is 50- Definition of class is 50- years of exposure to XC3 years of exposure to XS2, years of exposure to XF4, years of exposure to XA3, (Rh 65%) with 10%- with 10%-probability of with 10%-probability of ground water with SO 2 4 probability of carbonation chloride concentration scaling loss exceeding 6000mg/l and 10%- front exceeding (mm) exceeding 0,5% at depth (kg/m 2 ) probability of loss (mm) exceeding (g/m 2 )[??] ?? 9

10 Quoting fib State of the Art report on chloride ingress Would not going from left to right be nice 10

11 Draft proposal for text in EN Exposure resistance classes, continued (2) Concrete can be documented for the various classes in Table 2 by testing in accordance with the listed testing standards and with the limiting values given in Table 3. Table 3 Exposure resistance classes, limiting values and applicable test standards Carbonation resistance class RXC Chloride resistance class RXSD Frost resistance class RXF Limiting value, estimated after 50 years (mm) or kg/m 2 Classification standard RXC20 RXC30 RXC40 RXSD45 RXSD60 RXSD75 RXF0,5 RXF1, ,5 1,0 pren /12 EN CEN/TS CEN/TR (3) Concrete may also as an alternative to testing according to (2) be documented by applying the deemed to satisfy values in Annex F for the various cement/binders, water/binder ratios and minimum binder content. 11

12 PROPOSAL EN 206 Annex F Table F.1 Exposure resistance classes; deemed to satisfy values for various binder compositions (example, preliminary values) Tentative - Preliminary values Carbonation resistance class RXC Chloride resistance class RXSD Frost resistance class RXF RXC20 RXC30 RXC40 RXSD45 RXSD60 RXSD75 RXF0,2 RXF0,5 RXF1,0 Cement type or equivalent binder combination CEM I CEM II-A CEM II-B CEM III-A CEM III-B Maximum w/b-ratio b is the sum of cement and additions in the concrete, within the limits defining the cements according to EN ,55 0,60 0,65 NA NA 0,45 1 0,40 0,45 0,50 0,45 0,55 0,65 0,40 0,50 0,60??? 0,40 0,50 0,60 0,40 0,50 0,60??? NA 0,45 0,55?????? NA NA 0,45 0,38 0,45 0,55??? Minimum binder content (kg/m 3 ) Minimum air entrainment 4% 4% - 1 CEM I shall only be used with minimum 4% silica fume NA means that no deemed to satisfy values are given for that combination of binder and resistance class 12

13 The large scatter among the curves show how different the various cements within one cement type can perform with the same w/c-ratio 13

14 Alternative more refined approach distinguishing between various binders in Annex F of EN206 Preliminary values Cement type or equivalent binder combination CEM I Carbonation resistance class RXC Chloride resistance class RXSD RXC20 RXC30 RXC40 RXSD45 RXSD60 RXSD75 Frost resistance class RXF Maximum w/b-ratio b is the sum of cement and additions in the concrete, within the limits defining the cements according to EN ,55 0,60 0,65 NA NA 0,45 1 0,40 0,45 0,50 CEM II-A- V 0,45 0,55 0,65 0,40 0,50 0,60 S D L LL M CEM II-B- V 0,40 0,50 0,60 0,40 0,50 0,60 S D L LL M CEM III-A S NA 0,45 0,55??? CEM III-B S NA NA 0,45 0,38 0,45 0,55 Minimum binder content (kg/m 3 ) CEM I shall only be used with minimum 4% silica fume NA means that no deemed to satisfy values are given for that combination of binder and resistance class RXF 0,2 RXF 0,5 14 RXF 1,0

15 Exposure classes rate of carbonation and risk of corrosion 15

16 16

17 Class designation Description of the exposure Informative examples and comments 1 No risk of corrosion or attack For concrete without reinforcement or X0 embedded metal: all exposures except where there is freeze/thaw, abrasion or chemical attack 2 Corrosion induced by carbonation Where concrete containing reinforcement or other embedded metal is exposed to air and moisture, the exposure shall be classified as follows: XC1 Dry Concrete inside buildings with low air humidity, where the risk of corrosion is insignificant XC2 Wet or permanently high humidity, rarely dry Concrete surfaces subject to long-term water contact or permanently submerged in water or permanently exposed to high humidity. Many foundations, water containments (not external). Note: Leaching could also cause corrosion (see (5), XA classes). XC3 Moderate humidity Concrete inside buildings with moderate humidity External concrete sheltered from rain XC4 Cyclic wet and dry Concrete surfaces subject to cyclic water contact, (e.g. external concrete not sheltered from rain as walls, fassades, concrete in the tidal zone). 3 Corrosion induced by chlorides Where concrete containing reinforcement or other embedded metal is subject to contact with water containing chlorides, including de-icing salts, from sources other than from sea water, the exposure shall be classified as follows: XD1 Moderate humidity Concrete surfaces exposed to airborne chlorides XD2 Wet, rarely dry Swimming pools Concrete components exposed to industrial waters containing chlorides Note: If the chloride content of the water is 0.5 g/l then XD1 applies. XD3 Cyclic wet and dry Parts of bridges exposed to water containing chlorides Concrete roads, pavements and car park slabs in areas where de-icing agents are frequently used 4 Corrosion induced by chlorides from sea water Where concrete containing reinforcement or other embedded metal is subject to contact with chlorides from sea water or air carrying salt originating from sea water, the exposure shall be classified as follows: XS1 Exposed to airborne salt but not in direct Structures near to or on the coast, contact with sea water XS2 Permanently submerged Parts of marine structures and structures in seawater XS3 Tidal, splash and spray zones Parts of marine structures and structures directly over sea water 5. Freeze/Thaw Attack (XF classification is not necessary in cases where freeze/thaw cycles is rare) XF1 Moderate water saturation, without deicing Vertical concrete surfaces exposed to rain and freezing agent XF2 Moderate water saturation, with de-icing Vertical concrete surfaces of road structures exposed to freezing and airborne de-icing agents agent XF3 High water saturation, without de-icing Horizontal concrete surfaces exposed to rain and freezing agents XF4 High water saturation with de-icing agents or sea water Road and bridge decks exposed to de-icing agents Concrete surfaces exposed to direct spray containing de-icing agents and freezing Splash zone of marine structures exposed to freezing 6. Chemical attack XA1 Slightly aggressive chemical environment Natural soils and ground water according to Table 4.2 XA2 Moderately aggressive chemical Natural soils and ground water environment according to Table 4. 2 XA3 Highly aggressive chemical environment according to Table 4.2 Natural soils and ground water EN 1992 Table 4.1: Exposure classes related to environmental conditions Proposed changes; - X0 only for concrete without reinforcement - XC1 deleted permanently wet -XC2 added permanently wet 17

18 New 18

19 PROPOSAL in EN Table 4.4: Minimum concrete cover c min,dur dependant on design working life, exposure class and exposure resistance class Preliminary values Exposure Class EC Minimum cover for 50 and 100 years design working life, (preliminary values, values are rounded to nearest 5 mm) RXC20 2 RXC30 2 RXC years 100-years 50-years 100-years 50-years 100-years XC XC XC XC RXSD45 RXSD60 RXSD75 6 XD XS XD NA XS NA XD NA XS NA 1 Concrete corresponding to RXC10, with k N,90 1,4 mm/year 0,5 may be designed with c min = max {c min,b ; 10 mm} 2 The values are given for slab type geometry in beams the cover shall be increased by 5mm in RC20 and by 10 mm in RC30 and RC40 for exposure classes XC2, XC3, XC4, 3 In saline waters with chloride level below 2,0 % the minimum cover may be reduced by 10 mm, with a chloride level below 1,0 % the cover may be reduced by 15 mm, the tabulated values are applicable for Mediterranean and North Sea conditions (3 %). 4 Structures in regions with only short periods of use of de-icing salts, or low quantities annually, the minimum cover may be reduced by 10 mm, in agreement with provisions valid in the place of use. 5 The tabulated values for minimum cover assume curing class 2 according to EN (curing to 35% of f ck), where curing to curing class 3 or more is specified the cover may be reduced by 5 mm in exposure classes XC3, XC4, XD1, XD2, XD3 and XS1. 6 Concrete RXSD75 is not considered applicable for structures with 100 years design working life in exposure classes XD2, XD3, XS2 an d XS3 due to excessive cover requirements. 19

20 DtS values compared to minimum cover Tentative - Preliminary values Cement type or equivalent binder combination CEM I CEM II-A CEM II-B CEM III-A CEM III-B Carbonation resistance class RXC Chloride resistance class RXSD Frost resistance class RXF RXC20 RXC30 RXC40 RXSD45 RXSD60 RXSD75 RXF0,2 RXF0,5 RXF1,0 Maximum w/b-ratio b is the sum of cement and additions in the concrete, within the limits defining the cements according to EN ,55 0,60 0,65 NA NA 0,45 1 0,40 0,45 0,50 0,45 0,55 0,65 0,40 0,50 0,60??? 0,40 0,50 0,60 0,40 0,50 0,60??? NA 0,45 0,55?????? NA NA 0,45 0,38 0,45 0,55??? Minimum binder content (kg/m 3 ) Minimum air entrainment Preliminary 4% 4% - 1 CEM I shall only be used with minimum 4% silica values fume NA means that no deemed to satisfy values are given for that combination of binder and resistance class Exposure Class EC Sammenligning overdekning i mm Eksponeringsklasse RXC30 M60 XC XC XC XC RXSD60 M40 (M45) XD (M45) XS (M45) XD XS XD XS Minimum cover for 50 and 100 years design working life, (preliminary values, values are rounded to nearest 5 mm) RXC20 2 RXC30 2 RXC years 100-years 50-years 100-years 50-years 100-years XC XC XC XC RXSD45 RXSD60 RXSD75 6 XD XS XD NA XS NA XD NA XS NA

21 The durability concept is easy to apply for all parties involved; Exposure classes Exposure resistance classes Design working life Minimum concrete cover The designer will in the execution specification specify; Strength class, Exposure resistance class, chloride class, D upper /D lower and nominal cover as well as the Execution Class e.g C30/37 RXC30 Cl 0,20 D upper 32 D lower 16 c nom 30 mm (20+10) EXC3 The contractor will in the concrete specification specify; Strength class, Exposure resistance class, chloride class, consistence class, segregation resistance class etc. e.g C30/37 RXC30 Cl 0,20 D upper 32 D lower 16 S4 SR1 etc. The concrete producer produce and deliver a conforming concrete C30/37 RXC30 Cl 0,20 D upper 32 D lower 16 S4 SR1 21

22 91-days strength New cements and new bindercombinattions that reduces CO2- footprint Seems to give a slower strength development, a major part of the final strength comes after 28- days. 22

23 Present draft EC Strength (1) The compressive strength of concrete shall be denoted by concrete strength classes which relate to the characteristic (5%) cylinder strength f ck of the concrete in accordance with EN 206, determined at an age t ref. (2) The value for t ref should be taken as: (i) 28 days in general (ii) or may be taken between 28 and 91 days when specified for a project. Should be default, to become used and have effect on CO 2 23

24 EN 206 deals with re-cycled aggregates, but not from a design perspective, designers concern is within what limits of - Aggregate type (EN 12620) - Aggregate quantity (% replacement coarse and fine) - Intended concrete strength (upper limit) are design parameters used in EC2 unaffected? Within this range use of RA should be open for the Ready-mix producer Annex N (normative): Recycled aggregates concrete structures (1) Concrete with recycled aggregates may be used where the use of recycled aggregates will not impair durability, service performance like appearance or wear, or represent a risk of polluting water or air. Recycled aggregates may be used in normal concrete production without any particular consent if done in accordance with the provisions of EN 206. Note: The National Annex or the project specification can give further provisions and restrictions for the use of recycled aggregates for concrete. (7) For concrete of strength Class C30 and lower, recycled aggregates may be used in New clause and table regarding recycled aggregates. accordance with the parameters in Table 3.2. For higher strength classes or for higher Systematic review DK07 replacement values of the coarse fraction, including (2) replacement If the properties up to 10% listed of the in fines 5.1.2(3) for concrete with recycled aggregates are relevant for fraction, the design provisions of this standard may the be design applied in provided accordance it is demonstrated with this standard, by they should be determined by testing in tests that all values derived as a function of fck are accordance in accordance with with the the tests values specified given in Table in EN 206. The exposure resistance class should be 3.1. The procedure for testing and approval shall determined be given in the based execution on durability specification. performance testing. Table 3.2: Maximum fraction of recycled coarse aggregates (4/32) in strength class C30 and lower, for exposure resistance classes documented (3) All other by deemed clauses to of satisfy this standard values in are generally applicable, unless they are substituted by EN special provisions given in Table N.1. Recycled aggregates (4/32) Type according to EN RX0 RC40 RC30 RC20 RSD Type A 30% 30% 30% 20% 0 Type B 30% 30% 20% 0% 1 Where the resistance class is documented by tests with the actual recycled aggregates the maximum value may be taken as 30%. 24

25 The report express concern for creep, shrinkage and E- modulus, but also for normal density concrete there is a variation of +/- 30% There is also concern for shear, since failure mode can differ, but capacities are not lower than the reference. 25

26 The Goal is there Thank you for your attention