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CONCRETE CLASSIFICATION (IS-456)

CONCRETE CLASSIFICATION (IS-456). PRESCRIPTIVE (Nominal mix concrete)- Proportions and Characteristics of ingredients specified. PERFORMANCE BASED ( Design mix concrete) - Requirements of properties specified. Choice and proportioning of ingredients left to producer

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CONCRETE CLASSIFICATION (IS-456)

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  1. CONCRETE CLASSIFICATION (IS-456) • PRESCRIPTIVE (Nominal mix concrete)- Proportions and Characteristics of ingredients specified. • PERFORMANCE BASED ( Design mix concrete) - Requirements of properties specified. Choice and proportioning of ingredients left to producer • CONCRETE CAN BE CLASSIFIED SITUATION SPECIFIC ALSO e.g. LIGHT WEIGHT CONCRETE ETC.

  2. PROPERTIES OF CONCRETE • Fresh concrete - workability • Hardened concrete • STRENGTH • COMPRESSIVE • TENSILE • FLEXURAL • BOND • DURABILITY • CONCRETE IN FRESH AND HARDENED STATE HAS CONFLICTING DESIGN REQUIREMENTS.

  3. WORKABILITY • From the stage of mixing, transportation and placement upto compaction, concrete should be - • stable - No segregation or bleeding • cohesive and mobile • for proper placement • casting in required shape • amenable to compaction & • should give satisfactory surface finish • WORKABILITY IS THUS THE PROPERTY WHICH DETERMINE THE EASE WITH WHICH IT CAN BE MIXED, PLACED COMPACTED AND FINISHED.

  4. FACTORS AFFECTING WORKABILITY • Water - enough cement paste • Aggregates - • Size - sp. Surface area • shape - particle interference round flaky angular elongated • For a fixed water content, there is one optimum combination of coarse & fine aggregates giving highest workability if w/c ratio is constant. • Time - loss of water • Temperature

  5. REQUIREMENT OF WORKABILITY • TO BE DECIDED ON THE BASIS OF • CROSS SECTION OF THE MEMBER • REINFORCEMENT CONGESTION • AMOUNT OF AVAILABLE COMPACTION EFFORT • SPECIAL TRANSPORTATION OR PLACEMENT • TEMPERATURE AND TIME LAG • METHODS OF TESTING • SLUMP TEST • COMPACTION FACTOR TEST • VEE-BEE TEST

  6. COMPRESSIVE STRENGTH • Factors affecting: • W/C RATIO - S=K1/K2w/c • CEMENT CONTENT - OPTIMUM VALUE • CEMENT CHARACTERISTIC • AGE OF TESTING • PLACING, COMPACTION AND CURING

  7. DURABILITY • ABSENCE OF DURABILITY DUE TO • External factors • WEATHERING • ATTACK BY NATURAL/INDUSTRIAL LIQUIDS • Internal factors • ALKALI - AGGREGATE REACTION • NON COMPATIBLE THERMAL PROPERTIES • PRESENCE OF SULPHATES, CHLORIDES • CORROSION OF REINFORCEMENT DUE TO PRESENCE OF MOISTURE AND AIR

  8. DURABLE DESIGN • DURABILITY ENSURED BY PRESCRIBING • MAXM. W/C RAIO • TO CONTROL PERMEABILITY • MINM CEMENT CONTENT • COVER THICKNESS • TYPE OF CEMENT • AMOUNT OF SULPHATES • > 4% BY MASS OF CEMENT • AMOUNT OF CHLORIDES IN MOIST ENVIRONMENT • > 0.15% BY MASS OF CEMENT (RCC) • 0.06 % BY MASS OF CEMENT (PCC)

  9. REQUIREMENTS OF DURABILITY IS:456-1978 BUILDINGS ETC. • CEMENT REDUCED BY 10 PERCENT IF MAXM W/C RATIO STRICTLY CONTROLLED • THE MINIMUM CEMENT BASED ON 20 MM AGGREGATE. FOR 40 MM REDUCE BY ABOUT 10%; FOR 12.5 MM INCREASE BY ABOUT 10 %

  10. DEGREE OF Q.C. EXPECTED UNDER DIFFERENT SITE CONDITIONS

  11. VALUES OF STANDARD DEVIATION

  12. INPUT DESIGN PARAMETERSIS 10262 • CHARACTERISTIC STR. FCK =20 N1mm2 • WORKABILITY IN C.F. =0.90 • EXPOSURE CONDITION (MILD/MODERATE/SEVERE)= MILD • TYPE OF CONSTRUCTION ( PCC/RCC/PSC)= RCC • DEGREE OF QC EXPECTED =V.GOOD/GOOD/FAIR STANDARD DEVIATION = • TYPE OF CEMENT (A/B/C/D/E) =48 N/mm2/D • MAXM. SIZE OF C.A. = 20 mm • GRADING ZONE OF F.A. = ZONE III • SP. GR. OF C.A. = 2.6 • SP. GR. OF F.A. = 2.6 • SP. GR. OF CEMENT = 3.15. • TYPE OF AGG. (ROUND/ANGULAR)= ROUND

  13. APPROX SAND AND WATER CONTENT PER CUM. OF CONCRETE + SAND CONFORMING TO ZONE II 383-1970 * WATER CONTENT CORRESPONDING TO SATURATED SURFACE DRY. * WORKABILITY - COMPACTING FACTOR = 0.8 * USING ANGULAR AGGREGATES.

  14. PERCENTAGE ADJUSTMENTS IN WATER CONTENT AND SANDIS:10262 - 1982

  15. IS : 10 262 - 1982 • WHERE, • V = ABS. VOL. OF FRESH CONCRETE • W= MASS OF WATER PER m3 OF CONC. • C = MASS OF CEMENT PER m3 OF CONC. • Sc = SPEC. GRAVITY OF CEMENT • p = RATIO OF FA/TOTAL AGG. BY ABS. VOL. Fa, Ca - TOTAL MASSES OF FA AND CA IN KG/m3 OF CONC. Sfa, Sca - SPEC. GRAVITIES OF SATURATED SURFACE DRY FA AND CA.

  16. RAPID MIX DESIGN • DESIGN REFERENCE CONCRETE MIX W/C = 0.35 CF = 0.8 MSA = 10 mm FA = Zone II • DETERMINE ACCELERATED STRENGTH OF REFERENCE MIX USING BOILING WATER METHOD ( IS: 9013) • CHOOSE W/C FROM CURVES AT APP. B TO IS: 10262

  17. RAPID MIX DESIGN

  18. FREQUENCYOFSAMPLING • RANDOM • REPRESENTATIVE • SPREAD OVER ENTIRE PERIOD OF CONCRETING • COVER ALL MIXING UNITS QTY OF WORK M3NO. OF SAMPLES 1-5 1 6-15 2 16-30 3 31-50 4 51 & ABOVE4+1 FOR EACH 50 m3 OR PART THERE OF NOTE : AT LEAST ONE SAMPLE FROM EACH SHIFT SHALL BE TAKEN. TEST SPECIMEN: 3 FROM EACH SAMPLE ADDITIONAL FOR 7 DAY STRENGTH, PRESTRESSING.

  19. ACCEPTANCE CRITERIA (CONTD.) • CONCRETE OF EACH GRADE ASSESSED SEPARATELY • CONCRETE ASSESSED DAILY • CONCRETE LIABLE FOR REJECTION IF • POROUS, HONEY COMBED • PLACING INTERRUPTED WITHOUT CONSTRUCTION JOINT • REINFORCEMENT DISPLACED BEYOND TOLERANCES • CONSTRUCTION TOLERANCES NOT MET • HOWEVER HARDENED CONCRETE MAY BE ACCEPTED AFTER CARRYING OUT SUITABLE REMEDIAL MEASURES : • CORE TEST • LOAD TEST • NDT

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