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INNOVATIVE USE OF FINE AND ULTRA-FINE MATERIALS IN HIGH PERFORMANCE CONCRETE

INNOVATIVE USE OF FINE AND ULTRA-FINE MATERIALS IN HIGH PERFORMANCE CONCRETE. by Dr J D BAPAT AMBUJA CEMEMT: CONCRETE TALK NASHIK 19 OCTOBER 2012. CONVENTIONAL Vs HPC. CONVENTIONAL CONCRETE IS FOUND DEFICIENT IN: STRENGTH

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INNOVATIVE USE OF FINE AND ULTRA-FINE MATERIALS IN HIGH PERFORMANCE CONCRETE

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  1. INNOVATIVE USE OF FINE AND ULTRA-FINE MATERIALS IN HIGH PERFORMANCE CONCRETE by Dr J D BAPAT AMBUJA CEMEMT: CONCRETE TALK NASHIK 19 OCTOBER 2012

  2. CONVENTIONAL Vs HPC CONVENTIONAL CONCRETE IS FOUND DEFICIENT IN: • STRENGTH • DURABILITY IN SEVERE ENVIRONS: SHORTER SERVICE LIFE & HIGHER MAINTENANCE • CONSTRUCTION TIME: SLOWER STRENGTH GAIN & LONGER RELEASE TIME OF FORMS • ENERGY ABSORPTION CAPACITY: FOR EARTHQUAKE-RESISTANT STRUCTURES • HIGHER REPAIR AND RETROFITTING • DESIGNED TO EXCEED THE PERFORMANCE OF ORDINARY CONCRETE, HIGH PERFORMANCE CONCRETE (HPC) SUCCESSFULLY REMOVES THE ABOVE DEFICIENCIES.

  3. ACI DEFINITION OF HPC • HIGH-PERFORMANCE CONCRETE: • “CONCRETE MEETING SPECIAL COMBINATIONS OF PERFORMANCE & UNIFORMITY (UNIT WT., AIR CONTENT, SLUMP) REQUIREMENTS THAT CANNOT ALWAYS BE ACHIEVED ROUTINELY USING CONVENTIONAL CONSTITUENTS & NORMAL MIXING, PLACING & CURING PRACTICES”

  4. MEHTA & AITCIN DEFINITION • MEHTA AND AITCIN SUGGESTED THE TERM HIGH PERFORMANCE CONCRETE (HPC) FOR CONCRETE MIXTURES THAT POSSESS THE FOLLOWING THREE PROPERTIES: • HIGH-WORKABILITY • HIGH-STRENGTH & • HIGH DURABILITY

  5. HIGH PERFORMANCE CONCRETE • FLOWABILITY/PUMPABILITY: EASIER • WORKABILITY/COMPACTABILITY: EASIER • BLEEDING: NONE OR NEGLIGIBLE • FINISHING: QUICKER • SETTING TIME: QUICKER • EARLY STRENGTH (UP TO 7-DAY): HIGH • ULTIMATE STRENGTH- 90DAY: HIGHER • CRACK RESISTANCE: HIGHER • PLASTIC SHRINKAGE: LOWER (WITH PROPER CURING) • THERMAL SHRINKAGE: LOWER • DRYING SHRINKAGE: LOWER (WITH PROPER CURING) • DURABILITY • RESISTANCE TO PENETRATION OF CL IONS: VERY HIGH • ELECTRICAL RESISTIVITY: VERY HIGH • RESISTANCE TO REINFORCEMENT CORROSION: HIGH • RESISTANCE TO SULFATE ATTACK: VERY HIGH • RESISTANCE TO ALKALI-SILICA EXPANSION: VERY HIGH • COST • MATERIALS: DEPENDS UPON MIX • LABOR: SIMILAR • LIFE CYCLE: VERY LOW • ENVIRONMENTAL BENEFITS: CO2 EMISSION REDUCTION

  6. MICROSTRUCTURE: TRADITIONAL VERSUS HPC C3A + GYPSUM + WATER = ETTRINGITE = 3CaO.Al2O3.3CaSO4.32H2O

  7. CONCRETE & HPC IN INDIAN STANDARD • IS 456-2000 COVERS PLAIN & REINFORCED CONCRETE • BS 89 (2008) OF RDSO, INDIAN RAILWAYS GIVES GUIDELINES FOR HPC FOR BRIDGES

  8. COMPARISON: IS 456 & BS 89 FOR REINFORCED CONCRETE CONCRETE IS 456 HPC BS 89 (i) MINERAL ADMIXTURES FA, GGBS, SF, RHA, MK FA, GGBS, SF (ii) ADDITION LIMITS (%) FA: 15-35, GGBS: 25-70 FA: 20-35, GGBS: 50-70 (iii) CONCRETE M 20-M 80 M 40-M 80 (iv) CEMENT CONTENT (kg/cu.m) EXCLUDING ADMIXTURE (MAX) 450 450 INCLUDING ADMIXTURE (MIN) --- 380 (v) w/b RATIO(MAX) 0.4-0.55 0.33-0.4 (vi) CHLORIDE (MAX, kg/cu.m) 0.4-0.6* 0.2-0.3 (vii) SULPHATE SO3 (% CEMENT m) 4 4 (viii) CL ION PERMEABILITY -- < 800 COULOMBS (IX) DESIGN SHRINKAGE STRAIN 0.03% --- (X) CREEP COEFF @ 28 D LOADING 1.6** --- * INCLUDING PRE-STRESSED ** creep coeff. = (ultimate creep strain)/(elastic strain at the age of loading)

  9. SELECTED PROPERTIES ACHIEVABLE IN HPC • HIGH STRENGTH: 70-140 MPa @ 28-91 D • HIGH EARLY STRENGTH: 20-30 MPa @ 3-12 h OR 1-3 D • HIGH EARLY FLEXURAL STRENGTH: 2-4 MPa @ 3-12 h OR 1-3 D • HIGH MODULUS OF ELASTICITY > 40 GPa • ABRASION RESISTANCE: 0-1 mm DEPTH OF WEAR • LOW PERMEABILITY: 500-2000 COULOMBS • CHLORIDE PENETRATION < 0.07% Cl AT 6 MONTHS • LOW WATER ABSORPTION: 3-5%

  10. MORE THAN ONE TYPES OR PROPERTIES OF HPC MAY BE REQUIRED • MORE THAN ONE OF THE PROPERTIES OF HPC MENTIONED MAY BE REQUIRED FOR A GIVEN PROJECT • A HIGH RISE STRUCTURE MAY REQUIRE CONCRETE WITH HIGH-ULTIMATE STRENGTH, HIGH MODULUS OF ELASTICITY, HIGH PUMPABILITY & THE ABILITY TO BE PLACED WITHOUT CONSOLIDATION • MORE THAN ONE HPC MAY BE REQUIRED ON A PARTICULAR PROJECT • THE SAME HIGH-RISE STRUCTURE MAY ALSO REQUIRE A CONCRETE WHICH HAS A HIGH RESISTANCE TO CORROSION DAMAGE FOR AN ATTACHED PARKING STRUCTURE

  11. WHY MINERAL ADMIXTURES IN HPC? • HIGHER ULTIMATE STRENGTH • IMPROVED WORKABILITY • REDUCED BLEEDING • REDUCED HEAT OF HYDRATION • REDUCED PERMEABILITY • INCREASED RESISTANCE TO REINFORCEMENT CORROSION • INCREASED RESISTANCE TO CARBONATION • INCREASED RESISTANCE TO SULFATE ATTACK • INCREASED RESISTANCE TO ALKALI-AGGREGATE REACTIVITY (AAR) • LOWER OR COMPARABLE COSTS • REDUCED SHRINKAGE • BENEFITS VARY DEPENDING ON THE TYPE & QUALITY OF MINERAL ADMIXTURE, PROPORTION USED, OTHER MIX INGREDIENTS, MIXING PROCEDURE, FIELD CONDITIONS AND PLACEMENT.

  12. ADDITIONAL CEMENTITIOUS WITH MINERAL ADMIXTURES • SECONDARY HYDRATION: ONE OF THE PRIMARY BENEFITS OF MINERAL ADMIXTURE IS ITS REACTION WITH AVAILABLE LIME AND ALKALI IN CONCRETE, PRODUCING ADDITIONAL CEMENTITIOUS (C-S-H) COMPOUNDS: • C3S/C2S + H2O = C-S-H + Ca(OH)2 • Ca(OH)2 + SiO2 (FROM ADMIXTURE) = C-S-H

  13. LIMITATIONS OF MINERAL ADMIXTURES ➤ HIGH CARBON FLY ASH MAY REDUCE DURABILITY DUE TO ITS POTENTIAL FOR DECREASED AIR ENTRAINING ABILITY ➤ REDUCED EARLY STRENGTH ➤ REDUCED HEAT OF HYDRATION IN COLDER CLIMATES

  14. MINERAL ADMIXTURES • FLY ASH (FA) • BLAST FURNACE SLAG (BFS) • RICE HUSK ASH (RHA) • METAKAOLIN (MK) • SILICA FUME (SF) • For detail information, read Book: • Mineral Admixtures in Cement and Concrete by Dr J D Bapat, CRC Press, USA

  15. HPC FLY ASH

  16. RELEVANCE OF FA UTILISATION IN INDIA • COAL MAJOR FUEL FOR POWER GENERATION (.) 60% POWER PRODUCED USING COAL (.) INDIAN COAL HAS LOW CALORIFIC VALUE (3000-3500 k cal/kg) & VERY HIGH ASH CONTENT (30-45%) RESULTING IN HUGE ASH GENERATION (.) CURRENT ASH GENERATION 175 MILLION t/a • FA PRODUCED IN MODERN POWER STATIONS IS OF GOOD QUALITY(.) CONTAINS LOW S & VERY LOW UNBURNED C i.e. LESS LOI (.) MOST NEW THERMAL POWER STATIONS HAVE DRY FA EVACUATION & STORAGE SYSTEM (.) FA FROM ESP PNEUMATICALLY EVACUATED & STORED IN SILOS (.) FROM SILOS, IT IS LOADED IN OPEN TRUCK/ CLOSED TANKERS OR BAGGED • IN THE ESP, THERE ARE 6-8 FIELDS (ROWS) DEPENDING UPON DESIGN (.) FIELD AT THE BOILER END CALLED AS 1st FIELD & COUNTED SUBSEQUENTLY 2nd , 3rd ONWARDS (.) FIELD AT CHIMNEY END IS LAST(.) COARSE FA COLLECTED IN FIRST FIELDS. FINENESS OF FA PARTICLES INCREASES IN SUBSEQUENT FIELDS.

  17. FA PARTICLES ARE SPHERICAL & OF SIMILAR SIZE AS PORTLAND CEMENT PARTICLES Magnification 2000x

  18. FA REQUIREMENTS: IS 3812 • Fe2O3 + Al2O3 + SiO2 = MIN 70% (GRADE I, BITUMINOUS) & MIN 50% (GRADE II, LIGNITE) FOR GRADE I • SiO2 = MIN 35% • MgO = MAX 5% • SO3 = MAX 2.75% • ALKALIS = MAX 1.5% Na2O (Na2O + 0.658K2O) • LOI = MAX 12% • BLAINE FINENESS: MIN 320 m2/kg • 28 DAY COMPRESSIVE STRENGTH > 80% OF PLAIN CEMENT MORTAR • LIME REACTIVITY, DRYING SHRINKAGE AND SOUNDNESS BY AUTOCLAVE EXPANSION IS ALSO SPECIFIED

  19. SAMPLE FA: ASTM C618

  20. TUNNEL OF DELHI METRO RAIL CORPORATIONWHERE FA HAS BEEN USED

  21. TREMIE SEAL CONCRETE WITH FA IN BANDRA-WORLI SEA LINK PROJECT

  22. RAJASTHAN ATOMIC POWER PROJECT (RAPP) USED CONCRETE WITH FA

  23. FINE FA OR FFA • ALSO TERMED AS ULTRA-FINE FA • MEAN PARTICLE DIA OF CONVENTIONAL FA: 20-30 MICRONS • MEAN PARTICLE DIA OF FINE FA : 1-5 MICRONS • LOW UNBURNED CARBON • OBTAINED BY GRINDING &/OR AIR SEPARATION

  24. FFA REMOVES FA LIMITATIONS • HIGHER EARLY STRENGTH & HIGHER HEAT OF HYDARTION DUE TO FASTER & COMPLETE REACTION • BETTER DURABILITY WITH LESS CARBON & FINER PARTICLES REACTING COMPLETELY • AT 5-15% REPLACEMENT FFA CONTRIBUTES MORE TO CONCRETE STRENGTH GAIN & PERMEABILITY REDUCTION THAN COMMON FA & PERFORMS COMPARABLE TO HIGHLY REACTIVE POZZOLANA SUCH AS SILICA FUME • CONCRETE DURABILITY PROPERTIES LIKE RESISTANCE TO ALKALI-AGGREGATE REACTION, SULFATE ATTACK, CORROSION ARE ENHANCED BY FFA

  25. SF & FFA COMPARED • CONCRETE CONTAINING FFA COULD BE PRODUCED WITH ONLY 50% OF HIGH-RANGE WATER REDUCER (HRWR) DOSAGE IN COMPARISON TO SILICA FUME (SF) CONCRETE. • KEVIN D. COPELAND et. al. [IN “ULTRA FINE FLY ASH FOR HIGH PERFORMANCE CONCRETE” ASCE CONFERENCE, 2001] REPORT USE OF FFA WITH AV PARTICLE SIZE OF 3 MICRON & 90% < 7 MICRON

  26. HPC FA BLENDS WITH OTHER MINERAL ADMIXTURES

  27. LIGHTWEIGHT HPC WTH FA-MK BLEND BENICIA-MARTINEZ BRIDGE, SAN FRANCISCO BAY AREA CROSSING ACROSS THE CARQUINEZ STRAIT (2.3 km) CALIFORNIA DEPARTMENT OF TRANSPORTATION (CALTRANS) CASE STUDY PRESENTED BY GANAPATHY MURUGESH OF CALTRANS IN HPC BRIDGE VIEWS, ISS. 49, MAY-JUNE 2008

  28. LIGHTWEIGHT HPC WTH FA-MK BLEND BENICIA-MARTINEZ BRIDGE (2.3 km), CALIFORNIA DEPARTMENT OF TRANSPORTATION (CALTRANS) • ENGINEERING MARVEL WITH INCORPORATION OF SEVERAL UNIQUE DESIGN & CONSTRUCTION FEATURES • EVEN EXCLUDING THE 150 Y LIFE CYCLE ASPECT, INITIAL COST OF LIGHTWEIGHT CONCRETE, CAST-IN-PLACE SEGMENTAL STRUCTURE WAS LOWEST, IN COMPARISON TO: STEEL TRUSS BRIDGE; STEEL BOX-GIRDER BRIDGE; CONCRETE CABLE-STAYED BRIDGE. MORE THAN 30 MIX DESIGNS EVALUATED • BRIDGES: HPC IS REQUIRED FOR EARLY HIGH STRENGTH, GREATER SPAN, REDUCED DEPTHS OF MEMBERS • SPECIAL REQUIREMENT: BRIDGE REQUIRED TO SURVIVE & REMAIN OPEN TO TRAFFIC AFTER A MAJOR SEISMIC EVENT • KEY TO ACHIEVING LONG SPAN LENGTHS WAS THE CHOICE OF LIGHTWEIGHT HIGH PERFORMANCE CONCRETE

  29. LIGHTWEIGHT HPC WTH FA-MK BLEND BENICIA-MARTINEZ BRIDGE (2.3 km), CALIFORNIA DEPARTMENT OF TRANSPORTATION (CALTRANS) • SAND-LIGHTWEIGHT CONCRETE USED NORMAL WEIGHT SAND & LIGHTWEIGHT COARSE AGGREGATE TO PRODUCE CONCRETE WITH LOWER DENSITY (.) ANTICIPATED HIGHER CREEP & SHRINKAGE & LOWER MODULUS OF ELASTICITY CHARACTERISTICS EXPECTED WITH LIGHTWEIGHT CONCRETE, RESULTED IN STRINGENT MATERIAL PROPERTIES SPECIFIED FOR CONSTRUCTION • CONCRETE MIX PROPORTION (kg/cu.m): 494 (ASTM TYPE II-V) CEMENT, 29 FA (TYPE F), 58 MK, 509 SAND, 731 LIGHTWEIGHT AGG.,180 WATER FOR w/b = 0.31(.) SHRINKAGE-REDUCING, HYDRATION-STABILIZING, HRWR ADMIXTURE ADDED.

  30. LIGHTWEIGHT HPC WTH FA-MK BLEND BENICIA-MARTINEZ BRIDGE (2.3 km), CALIFORNIA DEPARTMENT OF TRANSPORTATION (CALTRANS) • SPECIFIC HPC PROPERTIES: • Density = 1920 kg/cu.m • Compressive strength = 69-76 MPa • 28-d modulus of elasticity = 26200 MPa • 180-d shrinkage = 0.042% • 365-d specific creep = 0.22 millionths/psi • QUALITY & CONSISTENCY OF LIGHTWEIGHT HPC ACHIEVED FOR OVER 46,000 CU M CONCRETE, OVER 2 Y PRODUCTION.

  31. HPC GROUND GRANULATED BLAST FURNACE SLAG (GGBS) • ONE t PIG IRON FRON BF GENERATES 250-350 kg SLAG (.) INDIA PRODUCES APPROX 10 MTPA BFS & 55% GETS UTILISED IN CEMENT (.) DEPENDS UPON GRANULATION CAPACITY.

  32. HIGH STRENGTH HPC WITHFINE GGBSREPORTED BY WANG LING et.al., CHINA BUILDING MATERIALS ACADEMY, PRC • GGBS < 4000 BLAINE F-GGBS: 5000-8000 BLAINE • C. AGG. (5-20 mm) = 1085, F. AGG. (2.9 mm) = 665 kg/m3 • BINDER = 500, w/b = 0.3, SLUMP = 230 mm, ADMIXTURE = 1.3% • COMPRESSIVE STRENGTH (MPa): CEMENT (43 G, 500 kg) CEMENT (350 kg) + 8000 B F-GGBS (150 kg) 3 D 56.4 76.7 7 D 60.0 88.3 28 D 70.7 93.6 60 D 74.1 99.0

  33. HPC SILICA FUME (SF)

  34. HPC WITH SF FOR HYDRO POWER STRUCTURE • REPORTED BY JITENDRA THAKUR, DY. CHIEF ENGINEER, JAYPEE (HYDRO DIV.) • TEHRI (UTTARANCHAL) HP SPILLWAY STRUCTURE • HPC REQUIRED FOR HIGHER RESISTANCE TO ABRASIVE, EROSIVE & CAVITATIONAL ACTION OF MOVING WATER (15,500cu.m/s, 55-60 m/s) (.) STRUCTURES ARE LINED/COATED WITH HPC TO ENHANCE PERFORMANCE.

  35. HPC WITH SF FOR HYDRO POWER STRUCTURE TYPICAL DAMAGED SPILLWAY

  36. HPC WITH SF FOR HYDRO POWER STRUCTURE TYPICAL CAVITATION ON SPILLWAY

  37. HPC MIX FOR TEHRI DAM PROJECT • M 70 MIX INGREDIENTS IN kg/cu.m • CEMENT 53 G 380 • SF 38 • CA-1 (20 mm) 680 • CA-2 (10 mm) 454 • FA-1 ( Crushed stone) 265 • FA-2 ( Natural sand) 491 • WATER 142 • SP (% m BINDER) 1.75 • w/b 0.34 • SLUMP (INITIAL), mm 185 • SLUMP (45 min), mm 120 • COMPRESSIVE STRENGTH, MPa • 3-D 51 • 7-D 61 • 28-D 75 • ABRASION RESISTANCE (%, 72 h)* HIGH SPEED (3360 rpm) 2.75 LOW SPEED (1100 rpm) 0.94 *ASTM C1138: Test container containing concrete specimen is submerged underwater. Steel balls of different diameters acting as foreign debris in water would be agitated by a rotating agitation paddle at a specific speed for a specific period, generally up to 72 h.

  38. HPC RICE HUSK ASH (RHA)

  39. RICE HUSK ASH (RHA) • OBTAINED FROM COMBUSTION OF RICE HUSK (RH) UNDER CERTAIN CONDITIONS OF SURROUNDING ENV., TEMP. & RES. TIME IN COMBUSTOR & SUBSEQUENT SIZE REDUCTION. • RHA FROM MODERN FLUIDISED OR CYCLONIC BED HAS HIGH SURFACE AREA: 20 - 40 m2/g, EVEN MORE (.) COMPARABLE WITH THAT OF SILICA FUME (SF) • APPLICATION NOT WIDELY COMMERCIALISED DUE TO: NON-AVAILABILITY OF RHA OF DESIRED POZZOLANIC CHARACTERISTICS ON A LARGE SCALE (.) LACK OF AWARENESS ABOUT POTENTIAL OF RHA AS MINERAL ADMIXTURE • BEHAVES DIFFERENTLY FROM SF DUE TO LARGE INTERNAL POROSITY

  40. RELEVANCE OF RHA FOR SUSTAINABILITY OF CONSTRUCTION INDUSTRY • PRESENTLY CONSIDERED AS AGRICULTURAL WASTE & USED AS FUEL • PADDY HAS POTENTIAL TO PRODUCE 4 % ITS MASS OF ASH • 2030 ASIA: 600 – 774 MT PADDY, 120 – 155 MT RH • HUGE SCOPE TO RECOVER RH HEAT VALUE (3300 – 3600 kcal/kg) TO GENERATE POWER & TO USE RHA PRODUCED IN CEMENT & CONCRETE

  41. REQUIREMENTS FOR LARGE SCALE APPLICATION OF RHA IN CONSTRUCTION • GOVT OF INDIA RHA MISSION: TO CREATE GENERAL AWARENESS ABOUT BENEFITS OF USING RH IN POWER GENERATION & RHA IN CEMENT & CONCRETE • VIABLE METHOD OF COLLECTION, TRANSPORTATION OF RH FROM PADDY FIELDS TO RHA PRODUCING UNIT • TECHNO-ECONOMICALLY FEASIBLE METHOD TO PRODUCE & PROCESS RHA ALONG WITH COGENERATION OF POWER, TO SUIT THE LOCAL CONDITIONS • NATIONAL STANDARDS ON THE QUALITY ASSESSMENT & THE USE OF RHA IN CEMENT & CONCRETE.

  42. HPC WITH RHAReported by: A. Salas et al. / Cement & Concrete Research 39 (2009) 773–778 • MATERIALS & MIX: • CEMENT: ASTM TYPE V PC, 3770 BLAINE, 28-D: 46.7 MPa • SF: m2/kg BET = 27000 & 0.1 MICRON AV. • T-RHA (UNTREATED): m2/kg BET = 24000 & 19 MICRON AV. • Ch-RHA (HCL TREATED): m2/kg BET = 2,74,000 & 17 MICRON AV. • BINDER: 440 kg/m3 WITH 10% SF/RHA, w/b = 0.45, SLUMP: 152-178 mm • AGGREGATE: FA-1 = - 2.38 mm, FA-2 = - 9.51 mm & CA BASALT = – 19 + 4.75 mm • SP: FORMALDEHYDE BASED, 0.4-1.9% • RHA REQUIRED HIGHER SP DOSAGE

  43. HPC WITH RHAReported by: A. Salas et al. / Cement & Concrete Research 39 (2009) 773–778 • STRENGTH & DURABILITY (TESTS AS PER ASTM) • FRESH CONCRETE REQUIRES HIGHER SP DOSAGE IN CASE OF RHA, IN COMPARISON TO CONTROL & SF • ELASTIC MODULUS (GPa) & FLEXURAL STRENGTH (RUPTURE MODULUS, MPa) ELASTIC FLEXURAL • CONTROL 29.1 3.7 • SF 31.8 5.1 • T-RHA 30.2 4.5 • Ch-RHA 32.1 5.4 • RAPID CHLORIDE ION PERMEABILITY TEST (RCPT, COULOMBS) COULOMBS • CONTROL 3529 MODERATE • SF 970 VERY LOW • T-RHA 1413 LOW • Ch-RHA 960 VERY LOW

  44. MIXING HPC • HORIZONTAL TWIN SHAFT CONCRETE MIXER FOUND TO PERFORM BETTER THAN DRUM TYPE IN TERMS OF LESSER MIXING TIME, IMPLYING GREATER ECONOMY IN OPERATION • FIRST MIX BINDER WITH A PORTION OF SP & PART OF WATER (.) THEN ADD AGGREGATE WITH REMAINING PORTION OF SP, DISSOLVED IN REST OF WATER.

  45. CURING HPC • MUST BE CURED QUITE DIFFERENTLY FROM ORDINARY CONCRETE DUE TO DIFFERENCE IN SHRINKAGE BEHAVIOR • WHEN HPC IS NOT WATER CURED IMMEDIATELY FOLLOWING PLACEMENT OR FINISHING, IT IS PRONE TO DEVELOP SEVERE PLASTIC SHRINKAGE BECAUSE IT IS NOT PROTECTED BY BLEED WATER & LATER ON DEVELOPS SEVERE AUTOGENOUS SHRINKAGE DUE TO ITS RAPID HYDRATION. • CRITICAL CURING PERIOD FOR ANY HPC RUNS FROM PLACEMENT OR FINISHING, UP TO 2-3 DAYS LATER & MOST CRITICAL PERIOD IS USUALLY BETWEEN 12-36 H. SHORT TIME DURING WHICH EFFICIENT WATER CURING MUST BE APPLIED TO HPC IS SIGNIFICANT ADVANTAGE OVER ORDINARY CONCRETE.

  46. CURING HPC • INITIATING WATER CURING AFTER 24 h IS TOO LATE (.) MOSTLY GREAT DEAL OF PLASTIC & AUTOGENOUS SHRINKAGE ALREADY OCCURRS & CAPILLARY/PORE NETWORK GETS DISCONNECTED IN MANY PLACES (.) COMPACT MICROSTRUCTURE DOES NOT ALLOW EXTERNAL WATER PENETRATE VERY DEEP INTO CONCRETE. • WATER PONDING OR FOGGING IS THE BEST WAY TO CURE HPC (.) ONE OF THESE TWO METHODS MUST BE APPLIED AS SOON AS POSSIBLE, IMMEDIATELY FOLLOWING PLACEMENT OR FINISHING. • WATER CURING CAN BE STOPPED AFTER 7 DAYS BECAUSE MOST CEMENT AT CONCRETE SURFACE GETS HYDRATED & FURTHER WATER CURING HAS LITTLE EFFECT ON DEVELOPMENT OF SHRINKAGE • BEST THING TO DO IS TO PAINT HPC OR TO USE A SEALING AGENT, SO THAT LAST WATER THAT REMAINS IN CONCRETE CAN BE RETAINED TO CONTRIBUTE TOWARDS HYDRATION

  47. ICI-JDBCERTIFICATE OF PROFICIENCY IN DURABILITY OF CONCRETE (C-PDC) • DATES: 20-24 (MON-FRI) MAY 2013 • VENUE: HOTEL RAVIRAJ, PUNE • DETAILS: http://www.drjdbapat.com • EMAILS: consult@drjdbapat.com consult.bapat@yahoo.com YOU ARE WELCOME

  48. Thanks!

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