Project on Concrete Mix Design for various grades of Concrete

• AIM : AIM OF MIX DESIGN:

AS CONCRETE IS A HETEROGENOUS MATERIAL THAT HAS VARIOUS INGREDIENT LIKE COARSE AGGREGATES ,FINE AGGREGATES,WATER ADMIXTURE ,ETC FOR MIXING FOR CONCRETE TO ACHIEVE THE DESIRED STRENGTH. THE SPECIFIC AMOUNT IS SELECTED SUCH THAT CONCRETE GIVES DESIRED WORKABILITY IN THE PLASTIC STAGE,DESIRED DURABILITY IN THE GIVEN ENVIRONMENT STATE,DESIRED STRENGTH IN THE HARDENED STATE AND ECONOMICAL CONCRETE AS POSSIBLE.

• INTRODUCTION:

PROJECT OF CONCRETE MIX DESIGN CONSIST OF TWO TYPE OF CONCRETE MIX DESIGN.

1. CONCRETE MIX DESIGN OF M35 IS DONE WITH FLYASH,SUPERPLASTICIZER,AND WET AGGREGATES.

2. CONCRETE MIX DESIGN OF M50 IS DONE WITHOUT FLYASH.

• OBJECTIVE : TO CALCULATE CONCRETE MIX DESIGN FOR M35 GRADE CONCRETE WITH FLYASH.

CODES USED: 10262:2019, IS 456:2000 .

1. TO ACHIEVE THE DESIRED WORKABILITY IN THE PLASTIC STAGE.
2. TO ACHIEVE THE DESIGNED MINIMUM STRENGTH IN THE HARDENED STAGE.
3. TO ACHIEVE THE DESIRED DURABILITY IN THE GIVEN ENVIRONMENT CONDITION.
4. TO PROCEDURE CONCRETE AS ECONOMICAL AS POSSIBLE.

• MATERIAL USED FOR CONCRETE MIX DESIGN.

STEP 1.

1. GRADE DESIGNATION :M35
2. TYPE OF CEMENT: OPC 43 GRADE CONFORMING OF IS 8112
3. TYPE OF MINERAL ADMIXTURE: FLYASH CONFORMING TO IS 3812(PART1)
4. MAXIMUM NOMINAL SIZE OF AGGREGATES : 20MM
5. MINIMUM CEMENT CONTENT: 320 KG/M^3.
6. MAXIMUM WATER CEMENT RATIO: 0.45(TABLE 5 OF IS 456:2000)
7. WORKABILITY : 75MM (SLUMP).
8. METHOD OF CONCRETE PLACING : PUMPING.
9. EXPOSE CONDITION: SEVERE(FOR RCC).
10. DEGREE OF SUPERVISION : GOOD.
11. TYPE OF AGGREGATES: CRUSHED ANGULAR AGGREGATES.
12. CHEMICAL ADMIXTURE TYPE : SUPERPLASTISIZER.

STEP 2.

TEST DATA FOR MATERIAL:

• CEMENT USED: OPC 43 GRADE CONFORMING TO IS 8112.
• SPECIFIC GRAVITY OF CEMENT : 3.15.
• SPECIFIC GRAVITY OF FLY ASH: 2.2.
• CHEMICAL ADMIXTURE TYPE: SUPERPLASTISIZER CONFORMING TO IS 9103.

SPECIFIC GRAVITY .

• coarse aggregates :2.74
• fine aggregates 2.74
• chemical admixture. 1 to 2.2

WATER ABSORPTION:

• COARSE AGREGATES: 0.5%
• FINE AGGREGATES: 0.1%.

FREE ( SURFACE) MOISTURE:

1. COARSE AGGREGATES .: NIL
2. FINE AGGREATED.: NIL

STEP 3.

PROCEDURE:

TARGET MEAN STRENGTH FOR MIX proportioning.

fck`= fck+1.65S

where, fck`= TARGET AVERAGE COMPRESSIVE STRENGTH AT 28DAYS.

fck= CHARACTERISTIC COMPRESSIVE STRENGTH AT 28 DAYS.

S = STANDARD DEVIATION.

FROM IS 10262:2019 TABLE 2 (CLAUSE 4.2.1.3) standard deviation S = 5N/MM^2.

THEREFORE, TARGET MEAN STRENGTH fck`=fck+1.65S

fck`= 35+1.65*5= 43.25N/MM^2

STEP 4. SELECTION OF WATER CONTENT RATIO:

FROM IS 456:2000 TABLE 5 MAXIMUM WATER CEMENT RATIO =0.45

BASED AS EXPERIENCE ,ADOPT WATER CEMENT RATIO AS =0.43

0.43<0.45 , HENCE OK.

STEP 5. SELECTION OF WATER CONTENT:

FROM IS 10262:2019, TABLE 4 (CLAUSE5.3), MAXIMUM WATER CONTENT = 186 LITRE .

( FOR 25 TO 50MM SLUMP RANGE ) FOR 20MM AGGREGATES.

NOTE: FOR ADDITIONAL SLUMP 3% MAY BE ADDED FOR EVERY 25MM SLUMP.

ESTIMATED WATER CONTENT FOR 75MM SLUMP =186+186*3/100 = 192 LITRES.

AS SUPERPLASTICIZER IS USED ,THE WATER CONTENT CAN BE REDUCED UP 20% AND ABOVE.

BASED ON TRIALS WITH SUPERPLASTICIZER WATER CONTENT REDUCTION OF 25% HAS BEEN ACHIEVED.

HENCE, THE ARRIVED WATER CONTENT =192*0.75= 144 LITRES.

STEP6. CALCULATION OF CEMENT CONTENT.

WATER CEMENT RATIO =0.43

CEMENT CONTENT = WATER/0.43 = 144/0.43 =335KG/M^3.

FROM IS 456:2000 TABLE 5 MINIMUM CEMENT CONTENT FOR SEVERE EXPOSURE CONDITION =320KG/M^3.

335 KG/M^3>320KG/M^3, HENCE OK.

• IF THE FLYASH IS USED IN THE CEMENT BY TRIAL AND EXPERIMENT INCREASE THE CEMENT CONTENT BY 10% AS THE FLYASH IS USED.

335*1.1= 369 KG/M^3

WATER CEMENT RATIO= WATER/CEMENT = 144/369= 0.393

• FLYASH IN THE CEMENT CONTENT IS @ 30% BY ITS WEIGHT.

369*0.3 = 111KG/M^3.

• CEMENT USED = 369*0.7=258 KG/M^3.

CEMENT QUANTITY SAVED DUE TO FLYASH ADDITION = 350-258 =92KG/M^3.

STEP7. PROPORTION OF VOLUME OF COARSE AGGREGATES AND FINE AGGREGATES CONTENT.

FROM IS 10262:2019 TABLE 5 VOLUME OF COARSE AGGRGATES CORRESPONDING TO 20MM SIZE AGGREGATES AND FINE AGGREGATES ( ZONE 1) FOR WATER CEMENT RATION OF 0.50=0.60

IN THE PRESENT CASE WATER CEMENT RATIO IS 0.43

THEREFORE, THE VOLUME OF COARSE AGGREGATES IS REQUIRED TO BE INCREASED TO DECREASED THE FINE AGGREGATES CONTENT .

AS THE WATER CEMENT RATIO IS LOWER BY 0.07

THE PROPORTION OF VOLUME OF COARSE AGGREGATES IS INCREASED BY 0.002 ( AT THE RATE -/+ 0.01 FOR EVERY +/- 0.05 CHANGE IN WATER CEMENT RATIO).

THERFORE, CORRECTED PROPORTION OF VOLUME OF COARSE AGGREGATES FOR THE WATER CEMENT RATIO :

0.07*0.01/0.05 =0.014

( 0.43=0.614) .

NOTES : IN CASE THE COARSE AGGREGATES IS NOT ANGULAR ONE,THEN ALSO VOLUME OF COARSE AGGREGATES MAY BE REQUIRED 10 BE INCREASED SUITABLY BASED ON EXPERIENCE.

FOR PUMPABLE CONCRETE THESE VALUE SHOULD BE REDUCED BY 10%

THEREFORE, VOLUME OF COARSE AGGREGATES = 0.614 * 0.9 = 0.55

VOLUME OF FINE AGGREGATES = 1 - 0.55 =0.45

STEP 8 . MIX CALCULATION :

THE MIX CALCULATION PER UNIT VOLUME OF CONCRETE SHALL BE FOLLOWS:

1. VOLUME OF CONCRETE =1 M^3
2. VOLUME OF CEMENT =( MASS OF CEMENT /SPECIFIC GRAVITY OF CEMENT ) * 1/1000 = ( 258/3.15 ) * 1/ 1000 =0.082/M^3
3. VOLUME OF WATER = ( MASS OF WATER /SPECIFIC GRAVITY OF WATER ) * 1/1000 = ( 144/1) * 1/1000 = 0.144 M^3
4. ( 111/ 2.2) * 1/1000 =0.050M^3
5. VOLUME OF CHEMICAL ADMIXTURE = ( MASS OF SUPERPLASTISIZER / SPECIFIC GRAVITY OF SUPERPLASTISIZER) * 1/1000 ( SUPERPLASTISIZER @ 2.0 % BY MASS OF CEMENTIOUS MATERIAL ) = ( 7.38 / 2.1 ) * 1/1000 = 0.0003 M^3 .
6. VOLUME OF AGGREGATES = VOLUME OF CONCRETE - ( VOL .OF CEMENT +VOL. OF FLYASH + VOL. OF WATER +VOL. OF CHEMICAL ADMIXTURE ) = 1 - ( 0.082+ 0.050+0.144+0.003) = 0.721M^3
7. MASS OF COARSE AGGREGATES IN AGGREGATES = VOL. OF ALL IN AGGREGATES * VOL. OF COARSE AGGREGATES * SPECIFIC GRAVITY OF COARSE AGGREGATES * 1000 = 0.721 * 0.55 *2.74 * 1000 = 1087 KG.
8. MASS OF FINE AGGREGATES = VOL. OF AGGREGATES * VOL. OF FINE AGGREGATES * SPECIFIC GRAVITY OF FINE AGGREGATES *1000 = 0.721 * 0.45 *2.74 * 1000 = 889 KG .

RESULTS:

CEMENT =258 KG/M^3.

FLYASH = 111 KG /M^3

WATER = 144 LITRES.

CHEMICAL ADMIXTURE = 7.38 KG/M^3

FINE AGGREGATES = 889 KG /M^3

COARSE AGGREGATES = 1087 KG /M^3

WATER CEMENT RATIO = 0.393

MIX PROPORTION FOR M35 GRADE = CEMENT : F.A : C.A

= 258: 889:1087

= ( 1 : 3.44 : 4.21 )

PART 2

AIM : TO CALCULATE THE CONCRETE IX DESIGN FOR M50 GRADE CONCRETE WITHOUT FLYASH.

CODE USED: 10262: 2019, IS 456 : 2000

STEP 1. MATERIAL USED:

1. GRADE DESIGNATION = M50
2. TYPE OF CEMENT = OPC 43 GRADE CONFORMING OF IS 8112.
3. MAXIMUM NORMAL SIZE OF AGGREGATE = 20MM.
4. MINIMUM CEMENT CONTENT = 360KG/M^3.
5. MAXIMUM WATER CEMENT RATIO = 0.43
6. WORKABILITY = 100MM ( SLUMP).
7. EXPOSURE CONDITION = EXTREME ( FOR RCC).
8. METHOD OF CONCRETE PLACING = PUMPING.
9. DEGREE OF SUPERVISION =GOOD.
10. TYPE OF AGGREGATES = CRUSHED ANGULAR AGGREGATES.
11. MAXIMUM CEMENT CONTENT = 450 KG/M^3.
12. CHEMICAL ADMIXTURE TYPE = SUPERPLASTISIZER.

STEP 2 . TEST DATA FOR MATERIAL :

• CEMENT USED : OPC 43 GRADE CONFORMING TO IS 8112.
• SPECIFIC GRAVITY OF CEMENT : 3.15
• CHEMICAL ADMIXTURE TYPE : SUPER PLASTISIZER CONFORMING TO IS 9103
• SPECIFIC GRAVITY :

1. COARSE AGGREGATES : 2.74
2. FINE AGGREGATES ; 2.74

• WATER ABSORPTION:

1. COARSE AGGREGATES: 0.5%
2. FINE AGGREGATES : 0.1%

• FREE (SURFACE ) MOISTURE :

1. COARSE AGGREGATES : NIL
2. FINE AGGREGATES: NIL

STEP 3. PROCEDURE:

TARGET MEAN STRENGTH FOR MIX PROPORTIONING: fck`=fck+1.65S

where, fck` = target average compressive strength as 28 days .

fck = characteristic compressive strength at 28 days.

S = standard deviation.

FROM IS 10262 : 2019 TABLE 2 STANDARD DEVIATION S = 5N/MM^2

THEREFORE , TARGET MEAN STRENGTH fck` = fck + 1.65 S

fck` = 50 + 1.65 *5 = 58.25n/mm^2.

STEP 4 . SELECTION OF WATER CEMENT RATIO :

FROM IS 456 : 2000 TABLE 5 , MAXIMUM WATER CEMENT RATIO = 0.4.

BASED ON EXPERIENCE , WE TAKE WATER CEMENT RATIO AS 0.38.

0.38<0.4 , HENCE O.K.

STEP 5. SELECTION OF WATER CONTENT:

FROM IS 10262 : 2019 ,TABLE 4 , MAXIMUM WATER CONTENT = 186 LITRES. ( FOR 25 TO 50 MM SLUMP RANGE ) FOR 20MM AGGREGATES.

NOTE: ( FOR ADDITIONAL SLUMP 3% MAY BE ADDED FOR EVERY 25MM SLUMP)

ESTIMATED WATER CONTENT FOR 100MM SLUMP = 186 + 186 *0.06 = 197 LITRES.

AS SUPERPLASTICIZER IS USED , THE WATER CONTENT CAN BE REDUCED UP 20% AND ABOVE .

BASED ON TRAIL WITH SUPERPLASTICIZER WATER CONTENT REDUCTION OF 20 PERCENT HAS BEEN ACHIEVED.

HENCE , THE ARRIVED WATER CONTENT = 197 * 0.80 = 157.6 ~ 158 LITRES.

STEP 6. CALCULATION OF CEMENT CONTENT :

WATER CEMENT RATIO = 0.38

CEMENT CONTENT = WATER CONTENT /0.38 = 158 / 0.38 = 415.78 ~ 416 KG/M^3.

FROM IS 456 : 2000 TABLE 5 , MINIMUM CEMENT CONTENT FOR EXTREME EXPOSURE CONDITION = 360 KG/M^3.

416 KG /M^3 > 360 KG/M^3 HENCE ,OK.

STEP 7 . PROPORTION OF VOLUME OF COARSE AGGREGATES AND FINE AGGREGATES CONTENT:

FROM IS 10262 : 2019, TABLE 5, VOLUME OF COARSE AGGREGATES CORRESPONDING TO 20MM SIZE AGGREGATES AND FINE AGGREGATES ( ZONE 1) FOR WATER CEMENT RATIO OF 0.50 = 0.60.

IN THE PRESENT CASE WATER CEMENT RATIO IS 0.38.

THEREFORE, THE VOLUME OF COARSE AGGREGATES IS REQUIRED TO BE INCREASED TO DECREASED THE FINE AGGREGATES CONTENT .

AS THE WATER CEMENT RATIO IS LOWER BY 0.12, THE PROPORTION OF VOLUME OF COARSE AGGREGATES IS INCREASED BY 0.03 ( AT THE RATE OF -/+ 0.01 FOR EVERY +/- 0.05 CHANGE IN WATER CEMENT RATIO ).

THEREFORE, CORRECTED PROPORTION OF VOLUME OF COARSE AGGREGATES FOR THE WATER CEMENT RATIO OF 0.38 = 0.60 + ( 0.12 * 0.01) / 0.05 = 0.624.

(0.38 = 0.624)

NOTE: IN CASE THE COARSE AGGREGATES IS NOT ANGULAR ONE THEN ALSO VOLUME OF COARSE AGGREGATES MAY BE REQUIRED 10 BE INCREASED SUITABLY BASED ON EXPERINCE.

FOR PUMPABLE CONCRETE THESE VALUES SHOULD BE REDUCED BY 10% .

THEREFORE, VOLUME OF COARSE AGGREGATES CONTENT = 0.624 * 0.9 = 0.56 .

VOLUME OF FINE AGGREGATES CONTENT = 1 - 0.56 = 0.44

STEP 8 . MIX CALCULATION :

THE MIX CALCULATIONS PER UNIT VOLUME OF CONCRETE SHALL BE AS FOLLOWS :

1. VOLUME OF CONCRETE = 1 M^3 .
2. VOLUME OF CEMENT = ( MASS OF CEMENT / SPECIFIC GRAVITY OF CEMENT ) * 1/1000, = ( 416 / 3.15 ) * 1/1000 = 0.132 M^3 .
3. VOLUME OF WATER = ( MASS OF WATER / SPECIFIC GRAVITY OF WATER ) * 1/1000 = ( 158 / 1 ) * 1/1000 = 0.158 M^3 .
4. VOLUME OF CHEMICAL ADMIXTURE = ( MASS OF SUPERPLASTICIZER / SPECIFIC GRAVITY OF SUPERPLASTICIZER ) * 1 / 1000 , = ( 8.32 / 2.1 ) * 1 / 1000 = 0.00396 M^3 . ( SUPERPLASTICIZER @ 2.0 PERCENT BY MASS OF CEMENTIOUS MATERIAL ) .
5. VOLUME OF AGGREGATES = VOL.OF CONCRETE - ( VOL OF CEMENT + VOL.OF WATER +VOL. OF CHEMICAL ADMIXTURE ) = 1 - ( 0.132 +0.158 + 0.00396) = 1 - 0.29396 = 0.70604 M/^3 .
6. MASS OF COARSE AGGREGATES = VOL. OF ALL IN AGGREGATES * VOL. OF COARSE AGGREGATES * SPECIFIC GRAVITY OF COARSE AGGREGATES * 1000 = 0.70604 * 0.56 *2.74 *1000 =1083.34 KG.
7. MASS OF FINE AGGREGATES = VOL. OF ALL IN AGGREGATES * VOL. OF FINE AGGREGATES * SPECIFIC GRAVITY OF FINE AGGREGATES * 1000 = 0.70604 * 0.44 * 2.74 * 1000 = 851.2 KG.

RESULTS : MIX PROPORTIONS FOR M50 CONCRETE :

CEMENT = 416 KG / M^3

CHEMICAL ADMIXTURE =8.32 KG/M^3

WATER = 158 LITRES

FINE AGGREGATES = 851.2 KG /M^3.

COARSE AGGREGATES = 1083.34 KG /M^3

WATER CEMENT RATIO = 0.38

MIX PROPORTION FOR M50 GRADE = CEMENT : F.A : C.A

= 416 : 851 : 1083

= (1 : 2.04 : 2.60)