CEL 774 CONSTRUCTION PRACTISES Mix design of Concrete: IS method B. Bhattacharjee CIVIL ENGINEERING DEPARTMENT IIT DELHI DEPARTMENT OF CIVIL ENGINEERING, IIT DELHI General Outline • The IS 10262 method • Example B. Bhattacharjee DEPARTMENT OF CIVIL ENGINEERING, IIT DELHI IS METHOD Step 1: f m =f ck + 1.65σ zThe standard deviations are: M10-M15: 3.5 MPa M20-M25: 4.0 MPa M30-M50: 5.0 MPa DETERMINE FROM SITE DATA, 30 CUBES B. Bhattacharjee DEPARTMENT OF CIVIL ENGINEERING, IIT DELHI IS METHOD áStep 2 : selection of w/c from curves B. Bhattacharjee DEPARTMENT OF CIVIL ENGINEERING, IIT DELHI IS METHOD áStep 2 : selection of w/c from curves B. Bhattacharjee DEPARTMENT OF CIVIL ENGINEERING, IIT DELHI IS METHOD áStep 3: Estimate water content & sand contents for concrete grades up to M35/ M35 above M35 m.s.a (mm) W kg/m3 p=Fagg Vol (%of Total) 10 208 40 20 186 35 40 165 30 B. Bhattacharjee DEPARTMENT OF CIVIL ENGINEERING, IIT DELHI IS METHOD áStep 3: Estimate water content & sand contents for concrete grades up to M35/ above M35 m.s.a (mm) W kg/m3 p=Fagg vol (%of Total) 10 200 28 20 180 25 B. Bhattacharjee DEPARTMENT OF CIVIL ENGINEERING, IIT DELHI IS METHOD áStep 3: Estimate water content & sand contents for concrete grades up to M35/ above M35 zThe Tables are for: Crushed CA Fine aggregate Zone II w/c =0.6(up to M35) & 0.35 (>M35) Compaction factor =0.8 B. Bhattacharjee DEPARTMENT OF CIVIL ENGINEERING, IIT DELHI IS METHOD áStep 3: Estimate water content & sand contents for concrete grades up to M35/ above M35 (Adjustments) Condition Adjusments Sand ZoneI,III,IV ΔW 0 -1.5% /zone (+ for I) CF(±) 0.1 w/c (±) 0.05 Rounded agg 3%(±) 0 -15 0 ±1% -7 Δp (%) B. Bhattacharjee DEPARTMENT OF CIVIL ENGINEERING, IIT DELHI IS METHOD áStep 4: Calculate cement content, Aggregate contents, ™ w/c*= Min (w/ccurve, w/cdurability) . ƒ C=Max(W/ w/c*, C durability). ⎡ C 1 Fagg ⎤ 1 V = ⎢W + + × ⎥× SC p S Fagg ⎥⎦ 1000 ⎢⎣ ⎡ Cagg ⎤ C 1 1 V = ⎢W + + × ⎥× SC (1 − p) SCagg ⎥⎦ 1000 ⎢⎣ B. Bhattacharjee DEPARTMENT OF CIVIL ENGINEERING, IIT DELHI IS METHOD ƒ V=1-air content m.s.a (mm) 10 Air content (%) 3.0 20 2.0 40 1.0 B. Bhattacharjee DEPARTMENT OF CIVIL ENGINEERING, IIT DELHI IS METHOD (Example) M25 concrete zCement 43 grade Moderate exposure Zone III sand Compaction factor 0.9 20 mm m.s.a rounded aggregate B. Bhattacharjee DEPARTMENT OF CIVIL ENGINEERING, IIT DELHI IS METHOD (Example) Step 1: f m =f ck + 1.65σ σ=4 Grade 25 SD TMS 4 31.6 f m = 32 MPa B. Bhattacharjee DEPARTMENT OF CIVIL ENGINEERING, IIT DELHI IS METHOD áStep 2 : selection of w/c from curves w/c =0.43 B. Bhattacharjee DEPARTMENT OF CIVIL ENGINEERING, IIT DELHI IS requirements (RCC) Exposure Min C Max w/c Min Grade Mild 300 0.55 M 20 Moderate Severe Very severe Extreme 300 320 340 360 0.50 0.45 0.45 0.40 M 25 M 30 M 35 M40 Step 2: w/c*=0.43, B. Bhattacharjee DEPARTMENT OF CIVIL ENGINEERING, IIT DELHI IS METHOD áStep 3: Estimate water content & sand contents for concrete grades up to M35/ M35 above M35 m.s.a (mm) W kg/m3 p=Fagg(%of Total) 10 208 40 20 186 35 40 165 30 B. Bhattacharjee DEPARTMENT OF CIVIL ENGINEERING, IIT DELHI IS METHOD áStep 3: Adjustments áΔW=(0.9-0.8)/0.1×0.03*186-15=-9.2 kg/m3 á Δ p (%)=-1.5+(0.43-0.6)×0.01/0.05-7=-11.9 Condition Adjusments ΔW Δp (%) Sand ZoneI,III,IV 0 -1.5% /zone(+ for I) CF(±) 0.1 3%(±) 0 w/c (±) 0.05 0 ±1% Rounded agg -15 -7 B. Bhattacharjee DEPARTMENT OF CIVIL ENGINEERING, IIT DELHI IS METHOD áStep 4: ™ w/c*= Min (0.43, 0.50)=0.43 . W=186-9.2≈177kg/m3 ƒ C=Max(177/ 0.43, 300). =411.6≈412 kg/m 3 ™p= 35-11.9=23.1 Fagg=419.25 kg/m3 Fagg ⎤ ⎡ 412 1 1 (1 − 0.02) = ⎢177 + + × ⎥× 3.15 0.231 2.7 ⎦ 1000 ⎣ Cagg= 1344.0kg/m3 Cagg ⎤ ⎡ 412 1 1 0.98 = ⎢177 + + × × ⎥ − 3 . 15 ( 1 0 . 231 ) 2 . 6 ⎣ ⎦ 1000 B. Bhattacharjee DEPARTMENT OF CIVIL ENGINEERING, IIT DELHI IS METHOD ™ W=186-9.2≈177kg/m3 ƒ C=Max(177/ 0.43, 300). =411.6≈412 kg/m 3 Fagg=419.25 kg/m3 Cagg= 1344.0kg/m3 Total= 2352 kg/m3 B. Bhattacharjee DEPARTMENT OF CIVIL ENGINEERING, IIT DELHI IS METHOD ™ Actual water to be added =177-water (present – absorption) in aggregate in kg/m3 ƒ Actual quantity of aggregate in the mix shall be Aggregate content + extra due to (moisture content- absorption) ™ Trial mix and final adjustment B. Bhattacharjee DEPARTMENT OF CIVIL ENGINEERING, IIT DELHI Summary IS method Example DEPARTMENT OF CIVIL ENGINEERING, IIT DELHI THANK YOU FOR HEARING DEPARTMENT OF CIVIL ENGINEERING, IIT DELHI