The Swiss P2P Road: from Theorecrete to Labcrete to Realcrete - PowerPoint PPT Presentation

RILEM Workshop Zagreb, 11 – 12 June 2014 The Swiss P2P Road: from Theorecrete to Labcrete to Realcrete Roberto Torrent Materials Advanced Services Ltd. Materials Advanced Services Ltd. 1425 Buenos Aires, Argentina 6877 Coldrerio, Switzerland info@m-a-s.com.ar www.m-a-s.com.ar

Objective � To present the evolution of the Swiss Standards for Durability, from purely Prescriptive (2003) to the most advanced Performance-based Standards worldwide (2013) � To show that it is possible to escape the “Prescriptive Trap” 2

Content � Year 2003: Prescriptive EN-based Standards � Year 2008: Performance requirements on cast specimens: o “Labcrete”: Laboratory Durability Indicators as step forward � Year 2013: Performance requirements on site concrete: o “Realcrete” vs “Labcrete”; Relevance of “Covercrete” for Durability � Conclusions 3

Year 2003: Prescriptive Standard SN EN206-1 • In 2003 Switzerland adopted the European Standards for Concrete: EN 206-1 and Eurocode 2 • In particular, for Durability, the following were adopted: � Exposure Classes (slightly modified in 2008) � Prescriptive requirements in terms of w/c max and C min , together with minimum strength classes for each Exposure together with minimum strength classes for each Exposure Class 4

Year 2003: Prescriptive Standard SN EN206-1 Carbonation-induced Chloride-induced Damage Corrosion Corrosion Exposure Class XC1 XC2 XC3 XC4 XD1 XD2a XD2b XD3 w/C max 0.65 0.65 0.60 0.50 0.50 0.50 0.45 0.45 C min (kg/m³) 280 280 280 300 300 300 320 320 f'c min (MPa) f'c (MPa) C25 C25 C25 C25 C30 C30 C37 C37 C30 C30 C30 C30 C37 C37 C37 C37 5

Prescriptive Standards: Shortcomings � The w/c ratio is a poor durability indicator, because it regards constituents as commodities : same mix proportions = same performance � The constraints to the mix proportions (C min and w/c max ) vary widely and are predominantly arbitrary � Offer little room for innovation and value adding � Offer little room for innovation and value adding � Limit the competitiveness of concrete as sustainable material � Compliance almost impossible to be checked by purchaser/owner 6

Prescriptive Standards refer to “Theorecrete” The author defines the prescriptive-specified concrete as “Theorecrete”, because it is based on expected (theoretical) assumptions seldom met in practice: � theoretical performance based on the specified w/c ratio � theoretical assumption that w/c ratio complies with prescribed limits (almost impossible to control on site) � theoretical good construction practices (frequently not theoretical good construction practices (frequently not observed by contractors, e.g. the endemic “lack of curing”) 7

Situation 2003 Presciptive specification of Theorecrete DESIGN PRACTICE CONTROL Impossibility Specification Concrete of checking of Production w/c w/c w/c max w/c max � � � � on Delivered Execution: Concrete • Placing � � � � Visual • Compaction Inspection • Finishing � � � � • Curing 8

Content � Year 2003: Prescriptive EN-based Standards o “Theorecrete”: The w/c max and Cement min Myths � Year 2008: Performance requirements on cast specimens: o “Labcrete”: Laboratory Durability Indicators as step forward � Year 2013: Performance requirements on site concrete: � Year 2013: Performance requirements on site concrete: o “Realcrete” vs “Labcrete”; Relevance of “Covercrete” for Durability � Conclusions 9

Year 2008: Theorecrete to Labcrete In 2008, performance requirements were introduced in the Swiss Standards, coexisting with prescriptive ones. Concrete producers must show through regular testing on cast specimens (“Labcrete“) that their concretes comply with limiting values of standard tests concretes comply with limiting values of standard tests Frequency = f (Volume, experience) ≥ 4 samples/year 10

Swiss Standards P2P: Carbonation Exposure Carbonation Class XC1 XC2 XC3 XC4 Accelerated Carbonation Strength 25 25 30 37 Class Cube min C min (kg/m³) 280 280 280 300 w/c max 0.65 0.65 0.60 0.50 K K N max (mm/√y) (mm/√y) --- --- 5.0 5.0 50 years K N max (mm/√y) --- --- 4.0 4.5 100 years 11

Swiss Standards P2P: Chlorides Capillary Suction Exposure Chlorides Class XD1 XD2a XD2b XD3 Strength 30 30 37 37 Class Cube min C min (kg/m³) 300 300 320 320 w/c max 0.50 0.50 0.45 0.45 q q w max (g/m²h) 10 10 10 10 --- --- --- --- Chloride Migration M Cl max --- --- 10 10 (10 -12 m²/s) 12

Situation 2008: from Theorecrete to Labcrete Performance specification of Labcrete DESIGN PRACTICE CONTROL Standard “K” Specification Concrete Tests on cast of Production Specimens Specimens K max K max ☺ ☺ ☺ ☺ K = Penetrability on Delivered (Performance) Execution: Concrete • Placing � � � � Visual • Compaction Inspection • Finishing � � � � • Curing 13

Content � Year 2003: Prescriptive EN-based Standards o “Theorecrete”: The w/c max and Cement min Myths � Year 2008: Performance requirements on cast specimens: o “Labcrete”: Laboratory Durability Indicators as step forward � Year 2013: Performance requirements on site concrete: � Year 2013: Performance requirements on site concrete: o “Realcrete” vs “Labcrete”; Relevance of “Covercrete” for Durability � Conclusions 14

“Labcrete” Plant or Site Production Sampling Delivery Specimen Preparation Moist Curing T~20°C ≥ 28 d. RH>95% Preconditioning Laboratory Testing 15

“Labcrete” Plant HSC Site Sampling, Sampling, Italy Romania Plant initial Curing, UK 16

“Labcrete” vs “Realcrete” Production Sampling Delivery Placing & Specimen Compaction Preparation Curing ? Curing ? Moist Curing T~20°C Natural ≥ 28 d. RH>95% Maturity “Realcrete” is quite different to “Labcrete” 17

“Realcrete” is very different to “Labcrete” Conveyors 18

Quality of Concrete in the Real Structure CO 2 Cl - SO 4 2- , Abrasion, Frost “Covercrete” of Poorer Quality Due to: Due to: Cast specimens, • Segregation made and cured under standard • Compaction conditions, DO • Curing NOT represent the Re-bars • Bleeding quality of the vital “covercrete” • Finishing • Microcracking 19

Covercrete weakening due to thermal microcracks Rhein Bridge Schaffhausen, Switzerland 1 Specimen M 1 m cube Pylon kT (10 -16 m²) 0.1 L 0.01 VL VL 0.001 HSC: f’c = 70 MPa Specimen at 20°C, >95% RH 20 Torrent R., ACI SP-186, Paper 17, pp. 291-308, 1999

Covercrete improvement: ShCC Floor Chemical Power prestressing due Floating to expansion ? restrained by steel Quartz hardener 21

Covercrete improvement: Use of Permeable Formwork Liners Without liner ? ? With liner kT ~ 1/10 Δw/c = 0.10-0.15 22

Recognition of “Covercrete” by Standards Swiss Concrete Code SIA 262:2003 ” With regard to durability, the quality of the cover concrete is of particular importance “ ”The ‘impermeability’ of the cover concrete shall be checked, by means of permeability tests (e.g. air permeability measurements) , on the structure or on cores taken from the structure “ 23

Air-Permeability Test Method: SIA 261/1 Annex E Vacuum Pump Valve 1 Valve 2 Touch-screen Computer 2-Chamber Pi Pe Vacuum cell Pressure Pressure Regulator (P e =P i ) 2-Chamber Vacuum cell i : Inner chamber e : External chamber i e Soft rings Concrete 24

Relation of kT with other Durability Indicators 25 100000 Water Sorptivity ASTM C1202 24-h Sorptivity (g/m²/s½) High (+ Very High) 20 10000 Coulombs 15 Moderate 10 Low 1000 Laboratory 5 Tunnel Very Bridge Low 0 100 0.001 0.01 0.1 1 10 100 0.001 0.001 0.01 0.01 0.1 0.1 1 1 10 10 100 100 kT (10 -16 m²) kT (10 -16 m²) kT (10 -16 m²) 150 20 Water Penetration Imamoto et al (~3.5y) Natural 18 Max. Penetration (mm) Torrent and Ebensperger (500 d) Carbonation Rate (mm/y ½ ) 125 under Pressure Carbonation Rate 16 Torrent and Frenzer (2y) (EN 12390-8) 14 100 12 75 10 8 50 6 25 4 2 0 0 0.001 0.01 0.1 1 10 0.001 0.01 0.1 1 10 100 kT (10 -16 m²) 28-d. kT (10 -16 m²) 25

Standard Method for site kT quality control SIA 262/1:2013 (Annex E) � Specification of kT s for different Exposure Classes � Grouping and Sampling (Lot = 500 m² or 3 d.) � 6 Tests at random within Lot � Suitable age (28 - 90 days), Temperature (≥ 10°C) and Surface moisture by impedance method (≤ 5.5%) � Conformity Rules 26

Specified Values of kT s Carbonation-induced Damage Chloride-induced Corrosion Corrosion Exposure Class XC1 XC2 XC3 XC4 XD1 XD2a XD2b XD3 w/C max 0.65 0.65 0.60 0.50 0.50 0.50 0.45 0.45 C min (kg/m³) 280 280 280 300 300 300 320 320 f'c min (MPa) C25 C25 C30 C37 C30 C30 C37 C37 KN max (mm/y ½ ) --- --- 5.0/4.0 5.0/4.5 --- --- --- --- qw qw max (g/m²/h) (g/m²/h) --- --- --- --- --- --- --- --- 10 10 10 10 --- --- --- --- MCl max (10 -12 m²/s) --- --- --- --- --- --- 10 10 kT s (10 -16 m²) site --- --- 2.0 2.0 2.0 2.0 0.5 0.5 kT s = upper «characteristic» value 27