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Mix Design EXAMPLES. EXAMPLE 1 WITH ppc. M40 grade with PPC (Annx A of IS 10262-2019). STIPULATIONS FOR PROPORTIONING a) Grade designation - M40 b ) Type of cement - PPC 43 grade conforming to IS 1489(Part-I) c ) Maximum nominal size of aggregate - 20mm
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EXAMPLE 1 WITH ppc
M40 grade with PPC (Annx A of IS 10262-2019) STIPULATIONS FOR PROPORTIONING a) Grade designation - M40 b) Type of cement - PPC 43 grade conforming to IS 1489(Part-I) c) Maximum nominal size of aggregate - 20mm d) Min. cement content as per table 3 & Max. water-cement ratio as per table 5 of IS 456 to be adopted. (320 kg/m3 & 0.45) f) Workability - 75 mm (slump) g) Exposure condition - Severe (for reinforced concrete) h) Method of concrete placing – Chute (Non pumpable) j) Degree of supervision - Good k) Type of aggregate - Crushed angular aggregate m) Maximum cement content - 450 kg/m3 n) Chemical admixture type - Superplasticizer
TEST DATA FOR MATERIALS • Cement used - PPC 43 grade conforming to IS 1489(Part-I) b) Specific gravity of cement – 2.88 c) Chemical admixture - Superplasticizer conforming to IS 9103 d) Specific gravity of: 1) Coarse aggregate (at SSD condition) – 2.74 2) Fine aggregate (at SSD condition) – 2.65 3) Chemical Admixture – 1.145 e) Water absorption: 1) Coarse aggregate - 0.5% 2) Fine aggregate – 1.0%
f) Moisture content of aggregate (As per IS 2386 (Part-3)): 1) Coarse aggregate - Nil 2) Fine aggregate - Nil g) Sieve analysis: 1) Coarse aggregate - Conforming to Table 7 of IS 383 2) Fine aggregate - Conforming to grading Zone II of Table 9 of IS 383
CALCULATIONS FOR MIX PROPORTIONING 1.TARGET STRENGTH FOR MIX PROPORTIONING f'ck= fck+ 1.65 S OR fck + X whichever is higher Where, f'ck= target average compressive strength at 28 days, fck= characteristic compressive strength at 28 days, and S= standard deviation. X = factor based on grade of concrete From Table 2 of IS 10262 standard deviation, S = 5 N/mm2 Table 1 of IS 10262, X = 6.5 Therefore, target strength a) f'ck = 40 + 1.65 x 5 = 48.25 N/mm2 b) f'ck = 40 + 6.5 = 46.5 N/mm2 Higher of the above - 48.25 N/mm2
2. Approximate Air content From Table 3, the approximate amount of entrapped air to be expected in normal (non-air-entrained) concrete is 1.0 percent for 20 mm nominal maximum size of aggregate. 3. Selection of water-cement ratio From Fig. 1, free w/c required for the target strength of 48.25 N/mm2 is 0.36 for OPC 43 grade curve. (For PPC, the strength corresponding to OPC 43 grade curve is assumed for the trial). From Table 5 of IS 456, maximum water-cement ratio = 0.45. prescribed for ‘severe’ exposure for reinforced concrete. 0.36 < 0.45, hence O.K.
4. SELECTION OF WATER CONTENT From Table 4, maximum water content = 186 kg for 20 mm aggregate, (for 25 to 50 mm slump range) Estimated water content for 75 mm slump = 186 + (3/100 X 186) = 191.58 kg As superplasticizer is used, the water content may be reduced. Based on trial data, the water content reduction of 23 percent is considered while using superplasticizer at the rate 1.0 percent by weight of cement. Hence the water content = 191.58 × 0.77 = 147.52 kg ≈ 148 kg
5. CALCULATION OF CEMENT CONTENT Water-cement ratio = 0.36 Cement content = 148/0.36 = 411.11 kg/m3 ≈ 412 kg/m3 From Table 5 of IS 456, minimum cement content for 'severe' exposure condition = 320 kg/m3 412 kg/m3 > 320 kg/m3, hence, O.K. From Table 4(c) of CBC, minimum cement content for 'severe' exposure condition = 350 kg/m3, hence, O.K.
6. PROPORTION OF VOLUME OF COARSE AGGREGATE AND FINE AGGREGATE CONTENT From Table 5,the proportionate volume of coarse aggregate corresponding to 20 mm size aggregate and fine aggregate (Zone II) for water-cement ratio of 0.50 = 0.62 In the present case, water-cement ratio is 0.36 Therefore volume of coarse aggregate is required to be increased to decrease the fine aggregate content. As the water-cement ratio is lower by 0.14, the proportion of volume of coarse aggregate is increased by 0.028 (at the rate of -/+ 0.01 for every ± 0.05 change in water-cement ratio). Therefore corrected proportion of volume of coarse aggregate for the water-cement ratio of 0.36 = 0.62 + 0.028 = 0.648
Volume of fine aggregate content = 1 – 0.648 = 0.352 7. MIX CALCULATIONS The mix calculations per unit volume of concrete shall be as follows: • Volume of concrete = 1 m3 • Volume of entrapped air in wet concrete = 0.01 m3 c) Volume of cement = Mass of cement x 1 Specific gravity of cement 1000 = 412/2.88 x 1/1000 = 0.143 m3 d) Volume of water = Mass of water x 1 Specific gravity of water 1000 = 148/1 x 1/1000 = 0.148 m3
e) Volume of chemical admixture (superplasticizer@ 1.0 percent by mass of cementitious material) = Mass of chemical admixture x 1 Specific gravity of admixture 1000 = 4.12/1.145 x 1/1000 = 0.0036 m3 g) Volume of all in aggregate = [(a-b) - (c +d+e)} = (1-0.01) - (0.143 + 0.148 + 0.0036) = 0.695 m3 h) Mass of coarse aggregate = g x Volume of coarse aggregate x Specific gravity of coarse aggregate x 1000 = 0.695 x 0.648 x 2.74 x 1000 = 1233.98 kg ≈ 1234 kg
j) Mass of fine aggregate = g x volume of fine aggregate x Specific gravity of fine aggregate x 1000 = 0.695 x 0.352 x 2.65 x 1000 = 648.29 kg ≈ 648 kg 7. MIX PROPORTIONS FOR TRIAL NUMBER 0 (TM-0) Cement = 412 kg/m3 Water = 148 kg/m3 Fine aggregate = 648 kg/m3 Coarse aggregate = 1234 kg/m3 Chemical admixture = 4.12 kg/m3 Free Water-cement ratio = 0.36
ADJUSTMENT ON WATER, FINE AND COARSE AGGREGATE (IF THE COARSE AND FINE AGGREGATE IS IN DRY CONDITION) a) Fine Aggregate (Dry) = Mass of fine aggregate in SSD condition 1 + water absorption /100 = 648 1+ 1/100 = 641.58 kg/m3 ≈ 642 kg/m3 b) Coarse Aggregate (Dry) = Mass of coarse aggregate in SSD condition 1 + water absorption /100 = 1234 1+ 0.5/100 = 1 227.86 kg/m3 ≈ 1 228 kg/m3
The extra water to be added for absorption by coarse and fine aggregate, • For coarse aggregate = Mass of coarse aggregate in SSD condition – mass of coarse aggregate in dry condition = 1 234 – 1 228 = 6 kg 2) For fine aggregate = Mass of fine aggregate in SSD condition – mass of fine aggregate in dry condition = 648 – 642 = 6 kg The estimated requirement for added water, therefore, becomes = 148 + 6 + 6 = 160 kg/m3
MIX PROPORTIONS AFTER ADUSTMENT FOR DRY AGGREGATES Cement = 412 kg/m3 Water (to be added) = 160 kg/m3 Fine aggregate (Dry) = 642 kg/m3 Coarse aggregate (Dry) = 1 228 kg/m3 Chemical admixture = 4.12 kg/m3 Free water-cement ratio = 0.36
Prepare the concrete mix with the above proportion of ingredients. (Trial mix TM-0) • Find out workability. • If workability is exactly same as required, i.e. 75 mm slump, then no further adjustment is made. • If measured workability is different from initially assumed, then water content adjustment will again be made keeping w/c ratio same. Final qty. of materials will again be calculated. (Trial mix TM-1) • Two more trial mixes TM-2 & TM-3 will be made, one with 10% less w/c and other with 10% more w/c but keeping water content same.
Now one sample (three cubes) with each trial mix is casted. • 28 days compressive strength is found out. • This strength is plotted against w/c ratio and a curve will be obtained. • From this curve, w/c ratio for the required TMS is found out for our design mix. • This w/c ratio is used to calculate again the ingredient quantities so that the mix prepared with these quantities will satisfy the requirements of not only strength but workability also. • The entire process is a DESIGN MIX.
EXAMPLE 2 WITH FLY ASH
M40 grade using Fly ash (Annx B of IS 10262-2019) STIPULATIONS FOR PROPORTIONING a) Grade designation - M40 b) Type of cement - OPC 43 grade conforming to IS 269 c) Type of mineral admixture- Fly Ash conforming to IS 3812 Part I d) Maximum nominal size of aggregate - 20mm e) Min. cement content as per table 3 & Maximum water-cement ratio as per table 5 of IS 456 to be adopted. (320 kg/m3 & 0.45) f) Workability - 120 mm (slump) g) Exposure condition - Severe (for reinforced concrete) h) Method of concrete placing – Pump j) Degree of supervision - Good k) Type of aggregate - Crushed angular aggregate m) Maximum cement content - 450 kg/m3 n) Chemical admixture type - Superplasticizer
TEST DATA FOR MATERIALS • Cement used - OPC 43 grade conforming to IS 269 b) Specific gravity of cement – 3.15 c) Fly Ash used – Conforming to IS 3812 Part I d) Specific gravity of Fly Ash – 2.2 e) Chemical admixture - Superplasticizer conforming to IS 9103 f) Specific gravity of: 1) Coarse aggregate (at SSD condition) – 2.74 2) Fine aggregate (at SSD condition) – 2.65 3) Chemical Admixture – 1.145 g) Water absorption: 1) Coarse aggregate - 0.5% 2) Fine aggregate – 1.0%
h) Moisture content of aggregate (As per IS 2386 (Part-3)): 1) Coarse aggregate – 2% 2) Fine aggregate – 5 % g) Free moisture content of aggregate Coarse aggregate free moisture content = 2.0-0.5 = 1.5 % Fine aggregate Free moisture content = 5.0- 1.0 = 4.0 %
CALCULATIONS FOR MIX PROPORTIONING 1.TARGET STRENGTH FOR MIX PROPORTIONING f'ck= fck+ 1.65 S OR fck + X whichever is higher Where, f'ck= target average compressive strength at 28 days, fck= characteristic compressive strength at 28 days, and S= standard deviation. X = factor based on grade of concrete From Table 2 of IS 10262 standard deviation, S = 5 N/mm2 Table 1 of IS 10262, X = 6.5 Therefore, target strength a) f'ck = 40 + 1.65 x 5 = 48.25 N/mm2 b) f'ck = 40 + 6.5 = 46.5 N/mm2 Higher of the above - 48.25 N/mm2
2. Approximate Air content From Table 3, the approximate amount of entrapped air to be expected in normal (non-air-entrained) concrete is 1.0 percent for 20 mm nominal maximum size of aggregate. 3. Selection of water-cement ratio From Fig. 1, free w/c required for the target strength of 48.25 N/mm2 is 0.36 for OPC 43 grade curve. From Table 5 of IS 456, maximum water-cement ratio = 0.45. prescribed for ‘severe’ exposure for reinforced concrete. 0.36 < 0.45, hence O.K.
4. SELECTION OF WATER CONTENT From Table 4, maximum water content = 186 kg for 20 mm aggregate, (for 50 mm slump ) Estimated water content for 120 mm slump = 186 (1+ (70/25)*.03) = 201.62 kg As superplasticizer is used, the water content may be reduced. Based on trial data, the water content reduction of 23 percent is considered while using superplasticizer at the rate 1.0 percent by weight of cement. Hence the water content = 201.62 × 0.77 = 155.25 kg ≈ 155 kg
5. CALCULATION OF CEMENT CONTENT Water-cement ratio = 0.36 Cement content = 155/0.36 = 430.55 kg/m3 ≈ 431 kg/m3 From Table 5 of IS 456, minimum cement content for 'severe' exposure condition = 320 kg/m3 431 kg/m3 > 320 kg/m3, hence, O.K. From Table 4(c) of CBC, minimum cement content for 'severe' exposure condition = 350 kg/m3, hence, O.K.
6. PROPORTION OF FLY ASH • To proportion a mix containing fly ash the following steps are suggested: • Decide the percentage fly ash to be used based on project requirement and quality of fly ash. • In certain situations, increase in cementitious material content may be warranted. The decision on increase in cementitious material content and its percentage may be based on experience and trials. • NOTE — This illustrative example is with increase of 10 percent cementitious material content.
Cementitiousmaterial content = 431 x 1.1 = 474.1 kg/m3 = 474 kg/m3 Water content = 155 kg/m3 So water cement ratio = 155/474 = 0.327 Fly Ash @ 30 % of Cementitiousmaterial = 474 x 0.3 = 142.2 kg/m3 = 142 kg/m3 Cement content = 474-142 = 332 kg/m3 From Table 5 of IS 456, minimum cementitious content for 'severe' exposure condition = 320 kg/m3 474 kg/m3 > 320 kg/m3, hence, O.K. From Table 4(c) of CBC, minimum cementitious content for 'severe' exposure condition = 350 kg/m3, hence, O.K.
6. PROPORTION OF VOLUME OF CA AND FA CONTENT From Table 5,the proportionate volume of coarse aggregate corresponding to 20 mm size aggregate and fine aggregate (Zone II) for water-cement ratio of 0.50 = 0.62 In the present case, water-cement ratio is 0.327 Therefore volume of coarse aggregate is required to be increased to decrease the fine aggregate content. As the water-cement ratio is lower by 0.173, the proportion of volume of coarse aggregate is increased by 0.0346 (at the rate of -/+ 0.01 for every ± 0.05 change in water-cement ratio). Therefore corrected proportion of volume of coarse aggregate for the water-cement ratio of 0.327 = 0.62 + 0.0346 = 0.6546 • For pumpable concrete these values may be reduced by up to 10 percent. (see 5.5.2). Here, 10 percent reduction is considered. • Therefore, volume of CA = 0.654 6 × 0.9 = 0.589 1, say 0.59 m3. • Volume of fine aggregate = 1 – 0.59 = 0.41 m3
7. MIX CALCULATIONS The mix calculations per unit volume of concrete shall be as follows: • Volume of concrete = 1 m3 • Volume of entrapped air in wet concrete = 0.01 m3 c) Volume of cement = Mass of cement x 1 Specific gravity of cement 1000 = 332/3.15 x 1/1000 = 0.105 m3 d) Volume of Fly Ash = Mass of fly ash x 1 Specific gravity of fly ash 1000 = 142/2.2 x 1/1000 = 0.0645 m3 e) Volume of water = Mass of water x 1 Specific gravity of water 1000 = 155/1 x 1/1000 = 0.155 m3
f) Volume of chemical admixture (superplasticizer@ 1.0 percent by mass of cementitious material) = Mass of chemical admixture x 1 Specific gravity of admixture 1000 = 4.74/1.145 x 1/1000 = 0.004 m3 g) Volume of all in aggregate = [(a-b) - (c +d+e+f)} = (1-0.01) - (0.105 + 0.0645+0.155 + 0.004) = 0.6615 m3 h) Mass of coarse aggregate = g x Volume of coarse aggregate x Specific gravity of coarse aggregate x 1000 = 0.6615 x 0.59 x 2.74 x 1000 = 1069.38 kg ≈ 1069 kg
j) Mass of fine aggregate = g x volume of fine aggregate x Specific gravity of fine aggregate x 1000 = 0.6615x 0.41 x 2.65 x 1000 = 718.71 kg ≈ 719 kg 7. MIX PROPORTIONS FOR TRIAL NUMBER 0 (TM-0) Cement = 332 kg/m3 Fly Ash = 142 kg/m3 Water = 155 kg/m3 Fine aggregate = 719 kg/m3 Coarse aggregate = 1069 kg/m3 Chemical admixture = 4.74 kg/m3 Free Water-cement ratio = 0.327
ADJUSTMENT ON WATER, FINE AND COARSE AGGREGATE (IF THE COARSE AND FINE AGGREGATE IS IN WET CONDITION) • Fine Aggregate (Wet) Mass of wet fine aggregate = Mass of fine aggregate in SSD condition X ( 1 + Free (surface) moisture /100) = 719 X ( 1+ 4/100) = 747.76 kg/m3 ≈ 748 kg/m3 b) Coarse Aggregate (Dry) Mass of wet coarse aggregate = Mass of coarse aggregate in SSD condition X ( 1 + Free (surface) moisture /100) = 1069 X ( 1+ 1.5/100) = 1085.03 kg/m3 ≈ 1085 kg/m3
The water to be added from coarse and fine aggregate as both are in wet condition, • For coarse aggregate = Mass of coarse aggregate in wet condition - Mass of coarse aggregate in SSD condition = 1085 – 1069 = 16 kg 2) For fine aggregate = Mass of fine aggregate in wet condition – mass of fine aggregate in SSD condition = 748 – 719 = 29 kg The estimated requirement to be deducted from water, therefore, quantity of water becomes = 155-16-29 = 110 kg/m3
MIX PROPORTIONS AFTER ADUSTMENT FOR WET AGGREGATES Cement = 332 kg/m3 Fly Ash = 142 kg/m3 Water (to be added) = 110 kg/m3 Fine aggregate (Wet) = 748 kg/m3 Coarse aggregate (Wet) = 1085 kg/m3 Chemical admixture = 4.74 kg/m3 Free water-cement ratio = 0.327 The total mass of coarse aggregate shall be divided into two fractions of 20 – 10 mm and 10 – 4.75 mm, in a suitable ratio, to satisfy the overall grading requirements for 20 mm max size aggregate as per Table 7 of IS 383 in the ratio of 60:40. Further process of trial mix and getting design mix is same as explained earlier.
EXAMPLE 3 WITH ggbs
M40 grade using GGBS (Annex. C of IS 10262:2019) STIPULATIONS FOR PROPORTIONING a) Grade designation - M40 b) Type of cement - OPC 43 grade conforming to IS 269 c) Type of mineral admixture- GGBS conforming to IS 16714 d) Maximum nominal size of aggregate - 20mm e) Min. cement content as per table 3 & Maximum water-cement ratio as per table 5 of IS 456 to be adopted. (320 kg/m3 & 0.45) f) Workability - 120 mm (slump) g) Exposure condition - Severe (for reinforced concrete) h) Method of concrete placing – Pump j) Degree of supervision - Good k) Type of aggregate - Crushed angular aggregate m) Maximum cement content - 450 kg/m3 n) Chemical admixture type - Superplasticizer
TEST DATA FOR MATERIALS • Cement used - OPC 43 grade conforming to IS 269 b) Specific gravity of cement – 3.15 c) GGBS used – Conforming to IS 16714 Part I d) Specific gravity of GGBS –3.0 e) Chemical admixture - Superplasticizer conforming to IS 9103 f) Specific gravity of: 1) Coarse aggregate (at SSD condition) – 2.74 2) Fine aggregate (at SSD condition) – 2.65 3) Chemical Admixture – 1.145 g) Water absorption: 1) Coarse aggregate - 0.5% 2) Fine aggregate – 1.0%
h) Moisture content of aggregate (As per IS 2386 (Part-3)): 1) Coarse aggregate – NIL 2) Fine aggregate – NIL
CALCULATIONS FOR MIX PROPORTIONING 1.TARGET STRENGTH FOR MIX PROPORTIONING f'ck= fck+ 1.65 S OR fck + X whichever is higher Where, f'ck= target average compressive strength at 28 days, fck= characteristic compressive strength at 28 days, and S= standard deviation. X = factor based on grade of concrete From Table 2 of IS 10262 standard deviation, S = 5 N/mm2 Table 1 of IS 10262, X = 6.5 Therefore, target strength a) f'ck = 40 + 1.65 x 5 = 48.25 N/mm2 b) f'ck = 40 + 6.5 = 46.5 N/mm2 Higher of the above - 48.25 N/mm2
2. Approximate Air content From Table 3, the approximate amount of entrapped air to be expected in normal (non-air-entrained) concrete is 1.0 percent for 20 mm nominal maximum size of aggregate. 3. Selection of water-cement ratio From Fig. 1, free w/c required for the target strength of 48.25 N/mm2 is 0.36 for OPC 43 grade curve. From Table 5 of IS 456, maximum water-cement ratio = 0.45. prescribed for ‘severe’ exposure for reinforced concrete. 0.36 < 0.45, hence O.K.
4. SELECTION OF WATER CONTENT From Table 4, maximum water content = 186 kg for 20 mm aggregate, (for 50 mm slump ) Estimated water content for 120 mm slump = 186 (1+ (70/25)*.03) = 201.62 kg As superplasticizer is used, the water content may be reduced. Based on trial data, the water content reduction of 23 percent is considered while using superplasticizer at the rate 1.0 percent by weight of cement. Hence the water content = 201.62 × 0.77 = 155.25 kg ≈ 155 kg
5. CALCULATION OF CEMENT CONTENT Water-cement ratio = 0.36 Cement content = 155/0.36 = 430.55 kg/m3 ≈ 431 kg/m3 From Table 5 of IS 456, minimum cement content for 'severe' exposure condition = 320 kg/m3 431 kg/m3 > 320 kg/m3, hence, O.K. From Table 4(c) of CBC, minimum cement content for 'severe' exposure condition = 350 kg/m3, hence, O.K.
6. PROPORTION OF GGBS • To proportion a mix containing GGBS the following steps are suggested: • Decide the percentage GGBS to be used based on project requirement and quality of GGBS. • In certain situations, increase in cementitious material content may be warranted. The decision on increase in cementitious material content and its percentage may be based on experience and trials.
GGBS @ 40 % of Cementitiousmaterial = 431 x 0.4 = 172.4 kg/m3 = 172 kg/m3 Cement content = 431-172 = 259 kg/m3 From Table 5 of IS 456, minimum cementitious content for 'severe' exposure condition = 320 kg/m3 431 kg/m3 > 320 kg/m3, hence, O.K. From Table 4(c) of CBC, minimum cement content for 'severe' exposure condition = 350 kg/m3, hence, O.K.
6. PROPORTION OF VOLUME OF CA AND FA CONTENT From Table 5,the proportionate volume of coarse aggregate corresponding to 20 mm size aggregate and fine aggregate (Zone II) for water-cement ratio of 0.50 = 0.62 In the present case, water-cement ratio is 0.36 Therefore volume of coarse aggregate is required to be increased to decrease the fine aggregate content. As the water-cement ratio is lower by 0.14, the proportion of volume of coarse aggregate is increased by 0.028 (at the rate of -/+ 0.01 for every ± 0.05 change in water-cement ratio). Therefore corrected proportion of volume of coarse aggregate for the water-cement ratio of 0.327 = 0.62 + 0.028 = 0.648 • For pumpable concrete these values may be reduced by up to 10 percent. (see 5.5.2). Here, 10 percent reduction is considered. • Therefore, volume of CA = 0.648 × 0.9 = 0.5832, say 0.58 m3. • Volume of fine aggregate = 1 – 0.58 = 0.42 m3
7. MIX CALCULATIONS The mix calculations per unit volume of concrete shall be as follows: • Volume of concrete = 1 m3 • Volume of entrapped air in wet concrete = 0.01 m3 c) Volume of cement = Mass of cement x 1 Specific gravity of cement 1000 = 259/3.15 x 1/1000 = 0.0822 m3 d) Volume of GGBS = Mass of GGBS x 1 Specific gravity of GGBS 1000 = 172/3 x 1/1000 = 0.0573 m3 e) Volume of water = Mass of water x 1 Specific gravity of water 1000 = 155/1 x 1/1000 = 0.155 m3
f) Volume of chemical admixture (superplasticizer@ 1.0 percent by mass of cementitious material) = Mass of chemical admixture x 1 Specific gravity of admixture 1000 = 4.31/1.145 x 1/1000 = 0.0038 m3 g) Volume of all in aggregate = [(a-b) - (c +d+e+f)} = (1-0.01) - (0.0822 + 0.0573+0.155 + 0.0038) = 0.6917 m3 h) Mass of coarse aggregate = g x Volume of coarse aggregate x Specific gravity of coarse aggregate x 1000 = 0.6917 x 0.58x 2.74 x 1000 = 1099 kg