Designing and Proportioning Normal Concrete Mixtures Chapter 9-Designing and Proportioning Normal Concrete Mixtures-EB101-7th Canadian Edition-2002

Factors in the Proportioning of Quality Concrete Mixtures Workability Durability Strength Appearance Economy

Materials Cement Supplementary Cementing Materials Water Aggregate Admixtures Fibres

Fig. 9-1. Trial batching verifies that a concrete mixture meets design requirements prior to use in construction (69899, 70008)

Mix Characteristics Strength Water-cementing materials ratio Aggregate size and volume Air content Slump and workability Water content Cementing materials content and type Admixtures

Definitions of Exposure Classes (1) Structurally reinforced concrete exposed to chlorides with or without freezing and thawing condition i.e. bridge and parking decks, ramps, portions of marine structures in tidal and splash zones C-2 Non-structurally reinforced (plain) concrete exposed to chlorides and F/T. i.e. garage floors, steps, pavements, sidewalks, curbs and gutters C-3 Continuously submerged concrete exposed to chlorides but not to F/T. i.e: underwater portions of marine structures

Definitions of Exposure Classes (2) Non-structurally reinforced concrete exposed to chlorides but not to F/T i.e. underground parking slabs on ground F-1 Concrete exposed to F/T in a saturated condition but not to chlorides. i.e. pool decks, patios, tennis courts, fresh water pools, and fresh water control structures F-2 Concrete in an unsaturated condition exposed to F/T but not chlorides. i.e. Exterior walls and columns N Conc. not exposed to chlorides or F/T. i.e. footings and interior slabs, walls and columns

Requirements for Classes of Exposure Class of exposure Max. w/cm Min. 28 d ƒcי (MPa) Air Content category C-1 C-2 C-3 C-4 F-1 F-2 N 0.40 0.45 0.50 0.55 For Str. 35 32 30 25 Design ** 1 2 1*** 2*** ** Use Category 1 for concrete exposed to F/T Use Category 2 for concrete not exposed to F/T *** Interior ice rinks slabs and freezer slabs with a steel trowel finish have been found to perform satisfactorily without entrained air.

Recommended Air Content Relative to Maximum Size Aggregate category Range in air content for conc. with indicated nominal max. sizes of coarse aggregates (%) 10 mm 14- 20mm 28-40 mm 1 6 to 9 5 to 8 4 to 7 2 3 to 6

Requirements for Concrete Subjected to Sulphate Attack Exposure Water- soluble sulphate SO4 in soil, ( %) Sulphate (SO4) in groundwater, mg/L Min. specified 56-day comp. str. MPa Max. w/cm Cementing Material to be used S-1 Very Severe Over 2.0 Over 10,000 35 0.40 50 S-2 Severe 0.20 to 2.00 1500 to 10,000 32 0.45 S-3 Moderate 0.10 to 0.20 150 to 1500 30 0.50 20E, 40, or 50E Table 9-2. Requirements for Concrete Subjected to Sulphate Attack Air content category for all exposures is 2. Exception is for steel-trowled interior slabs on grade in a non freeze thaw environment, air entrainment is not required. Type 50E cement shall not be used in reinforced concrete exposed to both chlorides and sulphates.

Relationship Between W/CM and 28-d Compressive Strength Fig. 9-2. Approximate relationship between compressive strength and water to cementing materials ratio for concrete using 20-mm to 28-mm nominal maximum size coarse aggregate. Strength is based on cylinders moist cured 28 days per CSA A23.2-3C. Adapted from Table 9-3, ACI 211.1, ACI 211.3, and Hover 1995.

Relationship between W/CM and 28- day Compressive Strength Compressive strength at 28 days, MPa Water-cementing materials ratio by mass Non-air-entrained concrete Air-entrained concrete 45 0.38 0.30 40 0.42 0.34 35 0.47 0.39 30 0.54 0.45 25 0.61 0.52 20 0.69 0.60 15 0.79 0.70 Table 9-3. Relationship Between Water to Cementing Materials Ratio and Compressive Strength of Concrete Strength is based on cylinders moist-cured 28 days in accordance with CSA A23.2-3. Relationship assumes nominal maximum size aggregate of about 20 to 28 mm. Adapted from ACI 211.1 and ACI 211.3.

Bulk Volume of Coarse Aggregate Fig. 9-3. Bulk volume of coarse aggregate per unit volume of concrete. Bulk volumes are based on aggregates in a dry-rodded condition as described in CSA A23.2-10A. For more workable concrete, such as may be required when placement is by pump, they may be reduced up to 10%. Adapted from Table 9-4, ACI 211.1 and Hover (1995 and 1998).

Bulk Volume of Coarse Aggregate Nominal Max. size of agg, (mm) Fineness modulus of sand 2.40 2.60 2.80 3.00 10 0.50 0.48 0.46 0.44 14 0.59 0.57 0.55 0.53 20 0.66 0.64 0.62 0.60 28 0.71 0.69 0.67 0.65 40 0.75 0.73 56 0.78 0.76 0.74 0.72 80 0.82 0.80 150 0.87 0.85 0.83 0.81 Table 9-4. Bulk Volume of Coarse Aggregate Per Unit Volume of Concrete Bulk volumes are based on aggregates in a dry-rodded condition as described in CSA A23.2-10A. Adapted from ACI 211.1.

Absolute Volume of Coarse Aggregate per m3 of Concrete Given: 0.46 m3 of coarse aggregate Bulk density = 1567 kg/m3, rodded Relative density = 2.65 Water = 1000 kg/m3 0.46 m3 • 1567 kg/m3 = 715.5 kg Absolute volume = 715.5/(2.65 • 1000) = 0.27 m3 1 m3 0.46 m3 So the coarse aggregate is 27% of the absolute volume of the concrete

Water and Air Require-ments for Different Slumps and Sizes of Aggregate Water, kilograms per cubic metre of concrete, for indicated sizes of aggregate Slump, mm 10 mm 14 mm 20 mm 28 mm 40 mm 56mm 80 mm 150 mm 25 to 50 207 199 190 179 166 154 130 113 75 to 100 228 216 205 193 181 169 145 124 150 to 175 243 202 178 160 — Approximate amount of entrapped air in non-air-entrained concrete, percent 3 2.5 2 1.5 1 0.5 0.3 0.2 Table 9-5). Approximate Mixing Water and Air Content Requirements for Different Slumps and Nominal Maximum Sizes of Aggregate. These quantities of mixing water are for use in computing cementing materials contents for trial batches. They are maximums for reasonably well-shaped angular coarse aggregates graded within limits of accepted specifications. The slump values for concrete containing aggregates larger than 40 mm are based on slump tests made after removal of particles larger than 40 mm by wet screening. Adapted from ACI 211.1 and ACI 318. Hover (1995) presents this information in graphical form. Non-air-entrained concrete

Water and Air Requirements for Differ-ent Slumps and Sizes of Aggregate Water, kilograms per cubic metre of concrete, for indicated sizes of aggregate Slump, mm 10 mm 14 mm 20 mm 28 mm 40 mm 56 mm 80 mm 150 mm 25 to 50 181 175 168 160 150 142 122 107 75 to 100 202 193 184 165 157 133 119 150 to 175 216 205 197 174 166 154 ― CSA A23.1 recommended ave. total air content, percent Category 1 6 to 9 5 to 8 4 to 7 Category 2 3 to 6 Table 9-5. Approximate Mixing Water and Air Content Requirements for Different Slumps and Nominal Maximum Sizes of Aggregate. These quantities of mixing water are for use in computing cementing materials contents for trial batches. They are maximums for reasonably well-shaped angular coarse aggregates graded within limits of accepted specifications. The slump values for concrete containing aggregates larger than 40 mm are based on slump tests made after removal of particles larger than 40 mm by wet screening. See Table 9-1 and 9-2 for class of exposure and corresponding air content categories. Adapted from CSA A23.1, ACI 211.1 and ACI 318. Hover (1995) presents this information in graphical form. Air-entrained concrete

Slump Test Fig. 16-2. Slump test for consistency of concrete. Left figure illustrates a lower slump, right figure a higher slump. (69786, 69787)

Recommended Slump Ranges Concrete construction Slump, (mm) Maximum Minimum Reinforced foundation walls and footings 75 25 Plain footings, caissons, and substructure walls Beams and reinforced walls 100 Building columns Pavements and slabs Mass concrete Table 9-6. Maximum slump may be increased by 25 mm for consolidation by hand methods, such as rodding and spading. Plasticizers can safely provide higher slumps. Adapted from ACI 211.1.

Approx. Water Requirements for Various Agg. Sizes and Slumps Fig. 9-4. Approximate water requirement for various slumps and crushed aggregate sizes for non-air-entrained concrete. Adapted from Table 9-5, ACI 211.1 and Hover (1995 and 1998).

Approx. Water Requirements for Various Agg. Sizes and Slumps Fig. 9-4. Approximate water requirement for various slumps and crushed aggregate sizes for air-entrained concrete. Adapted from Table 9-5, ACI 211.1 and Hover (1995 and 1998).

Minimum Cementing Materials Content for Flatwork Nominal max. size of aggregate, (mm) Cementing materials kg/m3 40 280 28 310 20 320 14 350 10 360 Table 9-7. Minimum Requirements of Cementing Materials for Concrete Used in Flatwork Cementing materials quantities may need to be greater for severe exposure. For example, for deicer exposures, concrete should contain at least 335 kg/m3 of cementing materials. Adapted from ACI 302.

Determination of Cement Content Required Water Content Cement Content = Water-Cement Ratio Example: air-entrained concrete 28-mm max. size agg. 75-mm slump w/c of 0.53 175 kg/m3 (Water) = 330 kg /m3 of concrete 0.53 (W/C-ratio)

Cementing Materials Requirements for Concrete Exposed to Deicing Chemicals Max. % (by mass) of total cementing materials Fly ash and natural pozzolans 25 Slag 50 Silica fume 10 Total of fly ash, slag, silica fume and natural pozzolans Total of natural pozzolans and silica fume 35 Table 9-8. Cementing Materials Requirements for Concrete Exposed to Deicing Chemicals Cementing materials include portion of supplementary cementing materials in blended cements. Total cementing materials include the summation of portland cements, blended cements, fly ash, slag, silica fume and other pozzolans. Silica fume should not constitute more than 10% of total cementing materials and fly ash or other pozzolans shall not constitute more than 25% of cementing materials. Adapted from ACI 318.

Maximum Chloride-Ion Content for Corrosion Protection Type of member Max. water-soluble chloride ion content in concrete, (%) by mass of cementing material Prestressed concrete 0.06 Reinforced concrete exposed to a moist environment or chlorides or both 0.15 Reinforced concrete exposed to neither a moist environment nor chlorides 1.00 Table 9-9. Maximum Chloride-Ion Content for Corrosion Protection Source CSA Standard A23.1

Methods for Proportioning Concrete Mixtures Water-cement ratio method Mass method Absolute volume method Field experience (statistical data) Trial mixtures

Proportioning from Field Data Modification Factor for Standard Deviation ( 30 Tests) Number of tests Modification factor for standard deviation Less than 15 see next slide (Table 9-11) 15 1.16 20 1.08 25 1.03 30 or more 1.00 Table 9-10. Modification Factor for Standard Deviation When Less Than 30 Tests Are Available Interpolate for intermediate numbers of tests. Modified standard deviation to be used to determine required average strength, f'cr. Adapted from ACI 318.

Proportioning from Field Data Required Strength When Data Are Not Available to Establish a Standard Deviation Specified compressive strength, f'c, MPa Required average compressive strength, f'cr, MPa Less than 21 f'c + 7.0 21 to 35 f'c + 8.5 Over 35 f'c + 10.0 Table 9-11. Required Average Compressive Strength When Data Are Not Available to Establish a Standard Deviation Adapted from ACI 318.

Proportioning from Field Data Required Strength When Data Are Available to Establish a Standard Deviation (CSA A23.1) f'cr = f'c+ 1.4s f'cr = f'c + (2.4s – 3.5 MPa) Required Average Compressive Strength When Data Are Available to Establish a Standard Deviation.

Proportioning from Field Data Required Strength When Data Are Available to Establish a Standard Deviation (ACI 318) Specified compressive strength, f'c, MPa Required average compressive strength, f'cr, MPa  35 f'cr = f'c+ 1.34s f'cr = f'c + 2.33s – 3.45 Use larger value Over 35 f'cr = 0.90f'c + 2.33s Required Average Compressive Strength When Data Are Available to Establish a Standard Deviation Adapted from ACI 318.

Proportioning from Field Data Required Strength When Data Are Not Available to Establish a Standard Deviation Specified compressive strength, f'c, MPa Required average compressive strength, f'cr, MPa Less than 21 f'c + 7.0 21 to 35 f'c + 8.5 Over 35 1.10f'c + 5.0 Table 9-11. Required Average Compressive Strength When Data Are Not Available to Establish a Standard Deviation Adapted from ACI 318.

Proportioning by Trial Mixtures Trial batching verifies that a concrete mixture meets design requirements prior to use in construction. Photo 87_13. The trial mixtures should use the same materials proposed for the work. Three mixtures with three different water-cementing materials ratios or cementing materials contents should be made. The trial mixtures should have a slump and air content within ±20 mm and ± 0.5%, respectively, of the maximum permitted. Three cylinders for each water-cementing materials ratio should be tested at 28 days.

Density of Water at Various Temperatures Temperature, °C Density, kg/m3 16 998.93 18 998.58 20 998.19 22 997.75 24 997.27 26 996.75 28 996.20 30 995.61 Table 9-12. Density of Water Versus Temperature

Absolute Volume Computation for Fine Aggregate Content 135 Water = = 0.135 m3 1 • 1000 435 Cement = = 0.138 m3 3.15 • 1000 7.0 Air = = 0.070 m3 100 Coarse aggregate = 1072 = 0.400 m3 2.68 • 1000 Subtotal = 0.743 m3 Fine aggregate volume = 1 - 0.743 = 0.257 m3 Fine aggregate mass = 0.257 • 2.64 • 1000 = 678 kg

Fig. 9-6. Trial mixture data sheet.

Result of Laboratory Trial Mixtures Batch no. Slump, mm Air content, percent Density, kg/m3 Cement content, kg/m3 Fine aggregate, percent of total aggregate Worka-bility 1 50 5.7 2341 346 28.6 Harsh 2 40 6.2 2332 337 33.3 Fair 3 45 7.5 2313 341 38.0 Good 4 36 6.8 2324 348 40.2 Table 9-13. Example of Results of Laboratory Trial Mixtures Water-Cement ratio was 0.45.

Relationship between Strength and Water to Cement Ratio Fig. 9-7. Relationship between strength and water to cement ratio based on field and laboratory data for specific concrete ingredients.

Example Trial Mixtures for Air-Entrained Concrete of 80-mm to 100-mm Slump W/C-ratio, kg per kg Nominal maximum size of aggregate,mm Air, % Water, kg/m3 of concrete Cement, kg/m3 of concrete With fine sand, FM = 2.50 Fine aggregate in % of total aggregate Fine aggre-gate, kg/m3 of concrete Coarse aggre-gate, 0.40 10 7.5 202 505 50 744 750 20 6 178 446 35 577 1071 40 5 158 395 29 518 1255 0.50 406 53 833 357 38 654 315 32 583 1225 Table 9-14. Example Trial Mixtures for Air-Entrained Concrete of Medium Consistency, 80- mm to 100- mm slump

Relationship between: Slump Agg. Size W/C Cement content Fig. 9-6. Example graphical relationship for a particular aggregate source demonstrating the relationship between slump, aggregate size, water to cement ratio, and cement content (Hover 1995).

Proportions to Make 1/10 m3 of Concrete for Small Jobs Nominal maximum size coarse aggregate, mm Air-entrained concrete Cement, kg Wet fine aggregate, Wet coarse aggregate, Water, 10 46 85 74 16 14 43 88 20 40 67 104 28 38 62 112 15 37 61 120 Table 9-15. Proportions by Mass to Make One Tenth Cubic Metre of Concrete for Small Jobs If crushed stone is used, decrease coarse aggregate by 5 kg and increase fine aggregate by 5 kg.

Proportions to Make 1/10 m3 of Concrete for Small Jobs Nominal maximum size coarse aggregate, mm Non-air-entrained concrete Cement, kg Wet fine aggregate, Wet coarse aggregate, Water, 10 46 94 74 18 14 43 85 88 20 40 75 104 16 28 38 72 112 15 37 69 120 Table 9-15. Proportions by Mass to Make One Tenth Cubic Metre of Concrete for Small Jobs If crushed stone is used, decrease coarse aggregate by 5 kg and increase fine aggregate by 5 kg.

Proportions by Bulk Volume of Concrete for Small Jobs Nominal maximum size coarse aggregate, mm Air-entrained concrete Cement Wet fine aggregate Wet coarse aggregate Water 10 1 2¼ 1½ ½ 14 2 20 2½ 28 2¾ 40 3 Table 9-16. Proportions by Bulk Volume* of Concrete for Small Jobs The combined volume is approximately 2/3 of the sum of the original bulk volumes.

Proportions by Bulk Volume of Concrete for Small Jobs Nominal maximum size coarse aggregate, mm Non-air-entrained concrete Cement Wet fine aggregate Wet coarse aggregate Water 10 1 2½ 1½ ½ 14 2 20 28 2¾ 40 3 Table 9-16. Proportions by Bulk Volume* of Concrete for Small Jobs The combined volume is approximately 2/3 of the sum of the original bulk volumes.

 Fig. 9-7. Flowchart for selection and documentation of concrete proportions.

Common Mix Design Mistakes Not varying water-cement ratio (3 point curve) Not monitoring slump loss during mix design to identify false setting tendency in cement Not monitoring early age concrete temperatures to identify retardation effects of water reducers