Construction Technology_Concrete Mix Design_Project 1

(i) Aim: calculation of concrete mix design of M35 grade of concrete with fly ash.

Stipulations for proportioning

• Grade: M35
• Type of cement: OPC 53
• Type of add-mixture: Fly ash (IS 3812 part-I)
• Maximum nominal size of aggregate: 20mm
• Minimum cement content: 320 Kg/m³ (Table 5 IS 456-2000, for severe exposure condition)
• Maximum water cement ratio: 0.45 (Table 5 IS 456-2000, for severe exposure condition)
• Workability: 100mm slump value for pumpable concrete.
• Exposure condition: severe for reinforced concrete.
• Method of concrete placing: pumping
• Degree of supervision: good
• Type of aggregate: crushed angular aggregate
• Maximum cement content: 450Kg/m³
• Chemical admixture type: superplasticizer.

Test data for materials

• Specific gravity of cement = 3.15
• Specific gravity of Fly ash = 2.2 (conforming to IS3812 (part I) )
• Chemical admixture = superplasticizer conforming to IS 9103
• Specific gravity of coarse aggregate = 2.74
• Specific gravity of fine aggregate = 2.74
• Water absorption of coarse aggregate = 0.5%
• Water absorption of fine aggregate = 1%
• Free surface moisture of coarse aggregate = NIL
• Free surface moisture of fine aggregate = NIL

Sieve analysis test

• Values of coarse aggregate conforming to Table 2 IS 383.
• Values of fine aggregate conforming to grading zone I of Table 4 IS 383.

Target strength of Mix proportioning

Target mean strength of concrete (f’ck)

f’ck = fck + 1.65S

fck = characteristic compressive strength at 28 days = 35N/mm²

S = standard deviation = 5.0 N/mm² (IS 10262-2009, table 1)

f’ck = 43.25 N/mm²

Water cement ratio selection:

From table 5 IS 456-2000, the W/C for severe exposure for reinforced concrete = 0.45

Based on experience, adopting W/C = 0.40

since, W/C = 0.40 < 0.45. Hence, safe.

Selection of Water content:

From table 2 IS 10262-2009, for aggregate of size 20mm, the maximum water content for slump values ranging from 25 to 50mm = 186kg = 186L

Therefore for slump value of 100mm, water content = 186 + (6/186) x 100 = 197L

(since for every 25mm increase in slump value, 3% of the value is added.)

As, superplasticizer is used, water content can be further reduced to 30%.

Based on trials, water content reduction of 29% is achieved with plasticizer.

Thus, water content = 197 x 0.71 = 140L.

Calculation of cement content:

W/C = 0.40

Water content = 140kg=140L

Therefore, cementatious content (cement + fly ash) = 140/0.40 = 350 Kg/m³.

From table 5 IS 456-2000, minimum cement content = 320Kg/m³ < 350 Kg/m³.

Hence, safe.

For proportioning of mix containing fly ash, following steps are adopted.

(a) The percentage of flyash needs to be decided based on project requirements and material quality.

(b) in some cases increase in cementeteous material is warrented. Here, we consider 10% increase in cementitious material.

Cementitious material content = 350 x 1.1 = 385 Kg/m³.

Water content = 140L

Therefore, W/C = 140/385 = 0.36

Fly ash @ 30% total cementitious material = 385 x 30% = 115 Kg/m³.

Cement (OPC) = 385 – 115= 270 Kg/m³.

Saving of cement while using fly ash = 350 – 270 = 80 Kg/m³

Fly ash being utilized = 115 Kg/m³

Volume of coarse and fine aggregate:

From Table 3 IS 10262:2009, fine aggregate ( zone 1) , water cement ratio= 0.40, 20mm size of aggregate

From table 3 , zone 1 and 20 mm size of aggregate, volume of coarse aggregate with W/C of 0.5 = 0.60

The present water cement ratio is = 0.40

The water cement ratio is lower by 0.1

so, for every 0.05 ,0.01 is increased

therefore ,the volume of coarse aggregate = 0.62

As the slump is 100mm ( pumpable concrete) so reduced by 10 % (100-10=90)

the volume of coarse aggregate = 0.62 * 90% = 0.56

volume of fine aggregate = 1- 0.56= 0.44

Mix design

(a) volume of concrete=1 m³

(b) volume of cement = (mass of cement/specific gravity of cement x 1000) = (270/3.15) x (1/1000)=0.086 m³( specific gravity of cement = 3.15)

(c) Volume of Fly ash = (mass of fly ash/specific gravity of fly ash x 1000) = (115/2.2) x (1/1000) = 0.052 m³ ( specific gravity of fly ash = 2.2)

(d) volume of water = (mass of water/specific gravity of waterx 1000) = (140/1) x (1/1000) = 0.140 m³ (specific gravity of water = 1)

(e) volume of superplasticizer = (mass of superplasticizer /specific gravity of superplasticizer x 1000) = (7.6/1.145) x (1/1000) =0.006 m³( specific gravity of admixture= 1.145 )

(f) volume of aggregates =(a−(b+c+d+e)) = 1−(0.086+0.052+0.140+0.006)= 0.716 m³

(g) mass of coarse aggregate = f x volume of coarse aggregate x specific gravity of aggregate x 1000= 0.716 x 0.56 x 2.74 x 1000=1098Kg/m³

(h) mass of fine aggregate = f x volume of fine aggregate x specific gravity of aggregate x 1000= 0.716 x 0.44 x 2.74 x 1000 = 863 Kg/m³.

MIX PROPORTION:

CEMENT: 270 Kg/m³

FINE AGGREGATE : 863 Kg/m³

COARSE AGGREGATE : 1098 Kg/m³

WATER CONTENT (W) = 140 Kg/m³

WATER CEMENT RATIO: 0.36

ADMIXTURE: 7 Kg/m³

MIX RATIO = 270 : 863:1098 (CEMENT : FINE AGGREGATE :COARSE AGGREGATE)

= 1 : 3.19 : 4.06

(ii) Aim: calculation of concrete mix design of M50 grade of concrete without fly ash.

Stipulations for proportioning

• Grade: M50
• Type of cement: OPC
• Maximum nominal size of aggregate: 20mm
• Minimum cement content: 320 Kg/m³ (Table 5 IS 456-2000, for exposure condition)
• Maximum water cement ratio: 0.45 (Table 5 IS 456-2000, for exposure condition)
• Workability: 100mm slump value for pumpable concrete.
• Exposure condition: severe for reinforced concrete.
• Method of concrete placing: pumping
• Degree of supervision: good
• Type of aggregate: crushed angular aggregate
• Maximum cement content: 450Kg/m³
• Chemical admixture type: superplasticizer.

Test data for materials

• Specific gravity of cement = 3.15
• Chemical admixture = superplasticizer conforming to IS 9103
• Specific gravity of coarse aggregate = 2.74
• Specific gravity of fine aggregate = 2.74
• Water absorption of coarse aggregate = 0.5%
• Water absorption of fine aggregate = 1%
• Free surface moisture of coarse aggregate = NIL
• Free surface moisture of fine aggregate = NIL

Sieve analysis test

• Values of coarse aggregate conforming to Table 2 IS 383.
• Values of fine aggregate conforming to grading zone I of Table 4 IS 383.

Target strength of Mix proportioning

Target mean compressive strength of concrete (f’ck)

f’ck = fck + 1.65S

fck = characteristic compressive strength at 28 days = 50 N/mm²

S = standard deviation = 5.0 N/mm² (IS 10262-2009, table 1)

f’ck = 58.25 N/mm².

Water cement ratio selection:

From table 5 IS 456-2000, the W/C for severe exposure for reinforced concrete = 0.45

From experience, adopted W/C = 0.40 < 0.45

Therefore, safe.

Selection of Water content:

From table 2 IS 10262-2009, for aggregate of size 20mm, the maximum water content for slump values ranging from 25 to 50mm = 186kg = 186L

Therefore for slump value of 100mm, water content = 186 + (6/186) x 100 = 197L

(since for every 25mm increase in slump value, 3% of the value is added.)

As, superplasticizer is used, water content can be further reduced to 30%.

Based on trials, water content reduction of 29% is achieved with plasticizer.

Thus, water content = 197 x 0.71 = 140L.

Calculation of cement content:

W/C = 0.40

Water content = 140kg=140L

Therefore, cementatious content (cement + fly ash) = 140/0.40 = 350 Kg/m³.

From table 5 IS 456-2000, minimum cement content = 320Kg/m³ < 350 Kg/m³.

Hence, safe.

Volume of coarse and fine aggregate:

From Table 3 IS 10262:2009, fine aggregate ( zone 1) , water cement ratio= 0.40, 20mm size of aggregate

From table 3 , zone 1 and 20 mm size of aggregate, volume of coarse aggregate with W/C of 0.5 = 0.60

The present water cement ratio is = 0.40

The water cement ratio is lower by 0.1

so, for every 0.05 ,0.01 is increased

therefore ,the volume of coarse aggregate = 0.62

As the slump is 100mm ( pumpable concrete) so reduced by 10 % (100-10=90)

the volume of coarse aggregate = 0.62 * 90% = 0.56

volume of fine aggregate = 1- 0.56= 0.44

Mix design

(a) volume of concrete=1 m³

(b) volume of cement = (mass of cement/specific gravity of cement x 1000) = (350/3.15) x (1/1000)=0.111 m³( specific gravity of cement = 3.15)

(c) volume of water = (mass of water/specific gravity of water x 1000) = (140/1) x (1/1000) = 0.140 m³ (specific gravity of water = 1)

(d) volume of superplasticizer = (mass of superplasticizer /specific gravity of superplasticizer x 1000) = (7.6/1.145) x (1/1000) =0.006 m³( specific gravity of admixture= 1.145 )

(e) volume of aggregates =(a−(b+c+d)) = 1−(0.111+0.140+0.006)= 0.743 m³

(f) mass of coarse aggregate =e x volume of coarse aggregate x specific gravity of aggregate x 1000= 0.743 x 0.56 x 2.74 x 1000=1140Kg/m³

(g) mass of fine aggregate = e x volume of fine aggregate x specific gravity of aggregate x 1000= 0.743 x 0.44 x 2.74 x 1000 = 896 Kg/m³.

Mix Proportion:

CEMENT: 350 Kg/m³

FINE AGGREGATE : 896 Kg/m³

COARSE AGGREGATE : 1140 Kg/m³

WATER CONTENT (W) = 140 Kg/m³

WATER CEMENT RATIO: 0.40

ADMIXTURE: 6 Kg/m³

MIX RATIO = 350 : 896:1140 (CEMENT : FINE AGGREGATE :COARSE AGGREGATE)

= 1 : 2.56 : 3.26