8. selection of concrete composition

Selection of Concrete Composition

UK term: Mix Design selection of mix ingredients and their proportions (DOE approach)

Ref: Design of normal concrete mixes, DOE, 1988)

American term: Mixture Proportioning (ACI approach)

Ref: Standard practice for selecting proportions for

normal, heavyweight, and mass concrete, ACI Manual of

concrete practice, Part 1: Materials and general

properties of concrete, ACI 211.1-91, 1994

The process aims to select constituent materials and their

proportions for concrete to meet specified requirements,

i.e. characteristic strength, consistence and durability

for exposure conditions in service and any special needs

The selected composition is adjusted based the results of a

trial batch applying knowledge on influencing factors Page 1 of 62


Important factors in selection of concrete composition:

Compressive strength

Commonly at 28-day characteristic value adopted in

structural design (structural adequacy)

Consistence (depends on construction processes)

Suitable for ease of placing, compacting and method of

transporting to point of placing after delivery

Durability (intended working life for exposure condition)

Currently deem-to-satisfied approach based on choice of

types of cement, maximum w/c ratio, minimum cement

and cover thickness based on qualitative classification of

exposure condition

Cost and other special requirements, e.g. surface finish Page 2 of 62


Exact determination of constituent proportions is NOT possible due to:

Variability of materials of nominal qualitative classification e.g. shape, texture and grading of aggregates

Lack of truly quantitative properties exactly linked to properties in quantitative terms e.g. water demand for given consistence

Empirical methods adopt tables and charts to provide first approximation of proportions as these are prepared from past experience for initial estimation only

For a new set of materials or requirements, initial test (trial mix) is conducted to assess resultant properties

Adjustment to proportions as necessary to achieve and/or to optimize composition for desired concrete properties, checked with further trials often needed

Page 3 of 62

Fundamentals Concepts

Duff Abrams (1918) formulated relationship between

compressive strength of concrete and water-cement

ratio in the form:

c = K1/K2(w/c)

c = compressive strength

A = empirical constant (96.5 MPa)

B = Constant that depends on cement properties (~4)

w/c = water to cement ratio by weight

Bcwc

A)/(5.1

c = 234 X3 (MPa) reported by Powers (1958)

Page 4 of 62


Feret (1896) established relationship:

c = K [c/(c + w + a)]2

where c = compressive strength

c, w, and a = absolute volumetric proportions of cement, water and air respectively

K = constant

This relationship includes volume of air and has been applied to cementitious systems with high air content e.g. foamed concrete (aerated or cellular concrete)

Air content up to 3% by volume in normal concrete taken into consideration in empirical approach

Higher air content by air-entraining admixture has to be compensated for reduction in compressive strength with lower water-cement ratio for similar strength

Page 5 of 62


Ideal aggregate grading Most dense aggregate-packing with a minimum content of voids

will be the most economical in theory

In practice, it is adequate to follow the grading limits specified by standards

Some basic rules for consistence (workability) Flowability

For a given slump, water requirement when

Max aggregate size

Content of angular or rough-textured aggregate particles

Content of entrained air

Cohesiveness

Improve cohesiveness

Increase sand/coarse aggregate ratio

Partial replacement of coarse sand by a fine sand

Increase cement/aggregate ratio (at given w/c)

Water content is main factor influencing consistence Page 6 of 62

Mix Design Process

Determine the job parameters

Strength

Durability requirements (if needed)

Consistence (Slump)

aggregate properties, max. aggregate size

water/cement ratio

Admixtures (for specific performance)

Calculate batch weights

Adjusting to the batch weights based on trial mix

Comment:

High durability concrete is expected to be also high

in strength, may be higher than used in structural

design Page 7 of 62

ACI Method (Mindess, 2002)

Step 1: Required information on materials to be used, properties on fine and coarse aggregates, dimensions of structural elements,

concrete strength and exposure conditions

Step 2: Choice of slump guidance from Table 10.1

Step 3: Maximum aggregate size depends of bar spacing and cover

Step 4: Estimation of mixing water (and air content if entrained air needed) guidance from Table 10.2

Step 5: Water/cement or water/cementitious material ratio guidance from Table 10.3 and Table 10.4 (severe exposure condition)

[Tables 10.5, 10.6 and 10.7 from CSA for specific exposure class]

Step 6: Calculation of cement or cementitious material content based on water content and water/cement ratio selected

Step 7: Estimation of coarse aggregate content guidance from Table 10.8

Step 8: Estimation of fine aggregate content guidance from Table 10.9 for fresh concrete density or based on volume of each ingredient to make

up 1 cubic meter

Step 9: Adjustment for moisture in the aggregates for batching weights

Step 10: Trial batch based on test results to adjust ingredient proportions to achieve required level Page 8 of 62

Required average strength ACI 214

(1) The probable frequency of the average of 3 consecutive tests below specified strength fc will not exceed 1 in 100

fcr = fc + 2.33 s/3 = fc + 1.34 s

where

fcr = required average compressive strength

fc = specified compressive strength

s = standard deviation

(2) (a) For fc 35 MPa, the probable frequency of tests more than 3.5 MPa below fc should not exceed 1 in 100

fcr = fc + 2.33 s - 3.5 (MPa)

(b) For fc > 35 MPa, the probable frequency of tests below 0.90fc should not exceed 1 in 100

fcr = 0.90 fc + 2.33 s

The required average compressive strength fcr is determined as the larger value of the above

(fcr and fc are cylinder compressive strength) Page 9 of 62

Required Average Strength (When Data Are Available to Establish a Standard Deviation)

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 3.5

Use larger value

> 35

f'cr = f'c+ 1.34s

f'cr = 0.90f'c + 2.33s

Use larger value

(ACI 214) Page 10 of 62

Number of tests

Modification factor for

standard deviation

Less than 15 Use Table 15.3

15 1.16

20 1.08

25 1.03

30 or more 1.00

Modification Factor for Standard Deviation

( 30 Tests)

s is multiplied by the above factor

(ACI 318)

Page 11 of 62

Required Average Strength (When There Are Insufficient Data to Establish s)

Specified compressive

strength,

f'c, (MPa)

Required average

compressive strength,

f'cr, (MPa)

Less than 20 f'c + 7.0

20 to 35 f'c + 8.5

Over 35 1.1f'c + 5.0

These estimates are very conservative, and should not be

used for large projects (over-design, non-economical)

(ACI 318)

Page 12 of 62

1. Required information Sieve analysis of fine and coarse aggregate, fineness

modulus

Dry-rodded unit weight of coarse aggregate

Bulk specific gravity of materials

Absorption capacity, or free moisture in the aggregate

Information on structure including the type and

dimensions of structural members, minimum space

between reinforcing bars

Required strength

Exposure conditions

Relationship between strength and w/c for available

combinations of cement and aggregate

Job specifications [e.g., max w/c, min. slump, strength at

early age (normally 28d), early temperature] Page 13 of 62

2. Choice of slump

Recommended Slump Ranges

Concrete construction Slump, mm

Maximum Minimum

Reinforced foundation walls and

footings 75 25

Plain footings, caissons, and

substructure walls 75 25

Beams and reinforced walls 100 25

Building columns 100 25

Pavements and slabs 75 25

Mass concrete 50 25

[(ACI 211.1) Table 10.1 Mindess] Page 14 of 62

3. Choice of maximum size of aggregate

Using a large max size of a well-graded aggregate

will produce less void space than using a smaller

size

Large aggregates minimize the amount of water

required, therefore reduce the amount of cement

required.

The maximum allowable aggregate size is limited by

the dimensions of the structural elements and

space between reinforcement

capabilities of construction equipment

Page 15 of 62

150

250

10

30 30 30 30

- Form: 150/5=30 mm

- Space between bars =30x3/4=22.5 mm

- Space between bar & form=25x3/4=19 mm

(assume: cover thickness = 25 mm)

Select aggregate with max. size 19 mm

(19 mm = 3/4 in. and 25 mm = 1 in.)

25 mm

Situation Maximum aggregate size

Form dimensions 1/5 of minimum clear distance

Clear space between reinforcement or prestressing

tendons

3/4 of minimum clear space

Clear space between reinforcement and form 3/4 of minimum clear space

Unreinforced slab 1/3 of thickness

Mindess

Page 16 of 62

4. Estimation of mixing water & air content

The quantity of water required to produce a given

slump is

dependent on the max size, shape and grading of

aggregate, amount of entrained air

not greatly affected by cement content

Estimation of water from Table 10.2 if no data are

available for a given aggregate

The recommendations in Table 10.2 are reduced for

other aggregate shapes than angular:

Shape Reduction in kg/m3

Sub-angular 12

Gravel with crushed particles 21

Round gravel 27

Page 17 of 62

Water and Air Requirements for Different Slumps and Sizes of Aggregate

Water, kg/m3 of concrete,

for indicated sizes of aggregate

Slump, mm 9.5

mm

12.5

mm

19

mm

25

mm

37.5

mm

50

mm

75

mm

150

mm

25 to 50 210 200 185 180 160 155 130 113

75 to 100 225 215 200 195 175 170 145 124

150 to 175 240 230 210 205 185 180 160

Approximate amount of

entrapped air in non-air-

entrained concrete,

percent

3 2.5 2 1.5 1 0.5 0.3 0.2

Non-air-entrained concrete (Extra from Table 10.2)

Based on well-shaped, angular coarse aggregate


Air entrainment requirements

Air entrainment is required whenever concrete is

exposed to freeze-thaw conditions

Air entrainment is also used for workability

The amount of the air required varies with

exposure conditions

mild: indoor or outdoor service where concrete

is not exposed to freezing and de-icing salts.

AEA may be used to improve workability

moderate: some freezing exposure occurs but

concrete not exposed to moisture

severe

size of the aggregates

Page 19 of 62

Water and Air Requirements for Different Slumps and Sizes of Aggregate

Water, kg/m3 of concrete,

for indicated sizes of aggregate

Slump, mm 9.5

mm

12.5

mm

19

mm

25

mm

37.5

mm

50

mm

75

mm

150

mm

25 to 50 180 175 165 160 145 140 120 107

75 to 100 200 190 180 175 160 155 135 119

150 to 175 215 205 190 185 170 165 155 -

Recommended average total air content,

percent, for level of exposure

Mild exposure 4.5 4.0 3.5 3.0 2.5 2.0 1.5 1.0

Moderate exposure 6.0 5.5 5.0 4.5 4.5 4.0 3.5 3.0

Severe exposure 7.5 7.0 6.0 6.0 5.5 5.0 4.5 4.0

Air-entrained concrete (Extract from Table 10.2


5. Selection of w/c or w/cm

Strength (Comment: Cylinder compressive strength)

Page 21 of 62

Cylinder

Compressive

strength at 28

days, MPa

Water/Cement Ratio by mass

Non-air-entrained

concrete

Air-entrained

concrete

45 0.37 -

40 0.42 -

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

If no historical data are available

- make trial batches with different w/c, establish a relationship between

strength and w/c

- estimation of w/c for the trial mixes from Table 10.3

Not applicable to ASTM Type II, III, IV, and V cements and blended

cements with very high quantities of pozzolans or GGBFS


5. Selection of w/c or w/cm

Durability

Checking w/c against the max. allowable w/c for

exposure conditions

Generally, more severe exposure conditions

require lower w/c

The minimum of the w/c for strength and durability

is selected for proportioning of the concrete

Page 23 of 62

6. Calculation of cement or cementitious material content

= mixing water (step 4) divided by the w/c (step 5)

if the concrete is used in flatwork, check minimum

cement content requirement

Nominal maximum size

of aggregate, mm

Cementing materials,

kg/m3

37.5 280

25 310

19 320

12.5 350

9.5 360

(ACI 318) Page 24 of 62

Cementitious Materials Requirements for

Concrete Exposed to Deicing Chemicals

Cementitious materials

Maximum % of

cementitious

materials

Fly ash and natural pozzolans 25

Slag 50

Silica fume 10

Total of fly ash, slag, silica fume

and natural pozzolans 50

Total of natural pozzolans and

silica fume 35

(ACI 318) Page 25 of 62

7. Estimation of coarse aggregate content

increase V, less workability (pavement)

reduce V, increased workability (pumping, shotcrete)

Maximum size of

aggregate, mm

Volume of dry-rodded coarse aggregate for

different fineness moduli of sand

2.40 2.60 2.80 3.00

9.5 0.50 0.48 0.46 0.44

12.5 0.59 0.57 0.55 0.53

19 0.66 0.64 0.62 0.60

25 0.71 0.69 0.67 0.65

37.5 0.76 0.74 0.72 0.70

50 0.78 0.76 0.74 0.72

75 0.82 0.80 0.78 0.76

150 0.87 0.85 0.83 0.81

Volume of Coarse Aggregate per Unit volume of Concrete

[(ACI 211.1) Table 10.8 Mindess Page 26 of 62

Coarse Aggregate Content per m3 of Concrete

Assume: Max. aggregate size = 9.5 mm

Fineness modulus of sand = 2.8

Volume of coarse aggregate in concrete

= 0.46 m3 of coarse aggregate/m3 concrete

Assume: Dry rodded unit weight = 1567 kg/m3 (oven dry)

Coarse aggregate content (Oven dry)

= 0.46 x 1567 kg/m3 = 715.5 kg/m3

Coarse aggregate content (SSD)

= 715.5 x (1+ A/100) [ A = Absorption capacity in %]

Page 27 of 62

8. Estimation of fine aggregate content

Mass (Weight) method

Wfa = Wc - Weight of other ingredients

Wfa = weight of fine aggregate

Wc = unit weight of concrete

Estimate according to Table 10.9

[(ACI 211.1) Table 10.9 Mindess]

Page 28 of 62

8. Estimation of fine aggregate content

Volume method

The components weight and specific gravity are used to

determine the volumes of the water, coarse aggregate, and

cement. These volume + volume of air are subtracted from

a unit volume of concrete to determine the V of fine

aggregate

1000 liters kg kg/l

convert the V to weight (generally using bulk SSD specific

gravity)

awcacemcon

awcacemconfa

VWWWV

VVVVVV

1/65.2/15.3/

Page 29 of 62

9. Adjustments for aggregate moisture

The mix proportions determined by steps 1 to 7 are

assumed to be on a saturated surface dry (SSD) basis.

If aggregate contains free moisture, the mixing water should

be and aggregates correspondingly according to the

amount of free moisture in the aggregates.

If aggregate is air dry, the mixing water should be and

aggregates correspondingly

Total water in aggregate absorption = free moisture

Page 30 of 62

Example:

Coarse aggregate, absorption capacity = 1%,

effective absorption = 0.5% (from air-dry to SSD)

Fine aggregate, absorption capacity = 1.3%, total

moisture content 4.5%

Assume a concrete mix proportion based on SSD:

Cement = 400 kg/m3, Water = 200 kg/m3, Coarse

aggregate = 1050 kg/m3, Fine aggregate = 710 kg/m3

Estimated unit weight = 2360 kg/m3

Actual mix proportion with the given aggregates

CA: 1050 1050x0.5% = 1045 kg/m3 (diff. = 5 kg/m3)

FA: free moisture = 4.5% 1.3% = 3.2%

710 + 710x3.2% = 733 kg/m3 (diff. = 23 kg/m3)

Water: 200 + 1050x0.5% - 710x3.2% = 182 kg/m3

Estimated unit weight = 2360 kg/m3

(Batching tolerance: 3% for aggregates, ?% for water) Page 31 of 62

10. Trial batch

Purpose

Verifies that a concrete mixture meets design requirements prior to use in construction.

Determine

Fresh concrete: slump, cohesiveness, segregation tendency, unit weight, air content, finishing

Hardened concrete: strength 28 days or other ages

Durability parameters if specified

Adjust concrete mixture accordingly

Strength does not meet requirement (workability ok)

Reduce w/c

Keep water content unaltered

Increase cement, reduce aggregate Page 32 of 62

10. Trial batch - continued

Adjust concrete mixture accordingly (contd)

Workability does not meet requirement (strength ok)

Keep w/c unaltered

Slump too low

Increase water and cement content

( 6 kg/m3 water will slump by ~25 mm)

Use WRA or superplasticizer

Slump too high

Reduce water and cement content

Reduce the dosage of WRA or SP

Segregation

Increase fine aggregate and reduce coarse aggregate

accordingly

Replace coarse sand with a finer sand

Air content: 1% air, reduce water by 3 kg/m3 Page 33 of 62

UK Approach DOE Method (Neville, 2011)

Step 1: Water/cement ratio based on typical relationships between compressive strength and water/cement ratio in Fig. 14.12, curve

for use selected from past experience of 28 day compressive

strength of concrete at water/cement of 0.5

Step 2: Water content for required consistence (slump) from Table 14.10 related to type of coarse aggregate (uncrushed or crushed) and

maximum aggregate size

Step 3: Cement content based on selected water/cement ratio and water content (at least equal to minimum cement content for durability,

guidance not provided)

Step 4: Total aggregate content for range of specific gravity of crushed or uncrushed coarse aggregate and fresh concrete density for

water content and specific gravity of coarse aggregate in Fig. 14.13

Step 5: Proportions of fine aggregate in total aggregate based on level of slump and free water /cement ratio for different percentage of fine

aggregate passing 600 m sieve and maximum aggregate size (20

mm or 40 mm) in Fig. 14.14

Comment:

In both ACI and DOE approach, guidance not provided on use of chemical

admixture and recommendations for different specific exposure conditions. Page 34 of 62

UK Approach Adopted in Singapore

Target mean strength, = characteristic strength + margin

fm = fcu,28 + ks

where

fm = mean cube compressive strength

fcu,28 = specified characteristic cube compressive strength

s = standard deviation

k = constant (= 1.64 for 5% defective)

EN 206: 2013 Annex A (normative) Initial Test

For initial testing, margin = 2 x standard deviation (6 to 12 MPa)

Comment:

Typical values for standard deviation range from 3 to 5 MPa for

most RMC plants.

Common margin selected = 7.5 to 8 MPa (s 4.5 to 5.0)

Page 35 of 62

1. Selection of water/cement ratio

Target mean strength is based on value adopted in design of concrete

structure (may not be the same for all

structural elements)

DOE method based on assuming certain strengths are related to

water/cement ratio of 0.5 for different

types of cements and aggregates Table 14.9 Neville

Current CEM l (42,5R) is similar to former rapid hardening Portland

(ASTM Type lll)

[w/c 0.5 50 MPa, approximately linear to w/c 0.3 80 MPa]

Fig. 14.12 Neville

Comment: Cube compressive strength

Page 36 of 62

a0104388Line

2. Selection of free water content for consistence

Free water content assumed main factor to achieve various levels of consistence (in terms of slump) (Table 14.10 Neville)

Three maximum size coarse aggregates : 10, 20, 40 mm

Two types of coarse aggregates considered:

Uncrushed (e.g. river gravel)

Crushed (higher water demand)

(Neville, 2011)

Page 37 of 62

3. Determination of cement content

Cement content = (water content)/ (water/cement ratio)

Limit for minimum cement content for durability

(EN 206 Table F.1 Annex F (informative)

Cement is the most costly not only on per unit mass basis but also for the amount in each unit volume of concrete

Cement has highest carbon footprint of all constituent materials in concrete

Minimum cement content achieved with minimum water content for consistence (including use of superplasticizers)

Limit for maximum cement content for development of heat of hydration in thick sections

Page 38 of 62

Durability Design of Concrete Structures

SS EN 206-1:2009

Clause 4.1 Exposure classes related to

environmental actions

NOTE The exposure classes to be selected

depends on the provisions valid in the place of

use of the concrete.

SS 544-1:2009 Concrete Complimentary Singapore Standard to SS EN 206-1 Part 1: Method of specifying and guidance for the

specifier

Table A.2 Classification of ground conditions

provides more detailed criteria for sulfate and

Tables A.1, A.4 and A.5 for exposure classes

(presentation on durability)

Page 39 of 62

4. Determination of total aggregate content

Estimate density of fully compacted fresh concrete indicated for selected water content (Step 2) and specific gravity of coarse

aggregate from chart (Fig. 14.13 Neville)

If specific gravity of coarse aggregate in not known, recommend value of 2.6 for uncrushed aggregate and 2.7 for crushed

aggregate

Total aggregate = concrete density cement content water content

(Neville, 2011)

Page 40 of 62

5. Determination of proportion of fine aggregate

Bases for selection include level of consistence, water/cement ratio and fineness of fine aggregate (percentage of fine aggregate

passing 600 m sieve (likely range 40 to 60%)

Determine proportion of fine aggregate in term of percent of total aggregate (Step 4) - Fig. 14.14 Neville

Fine aggregate content = % fine aggregate x total aggregate content

Coarse aggregate content = total aggregate content minus fine aggregate content

Recommend coarse aggregate divided into different single sized aggregates in proportions shown below

Total coarse aggregate 5 10 mm 10 20 mm 20 40 mm

100 33 67 -

100 18 27 55

Comment: approximately 1:2 between adjacent sizes Page 41 of 62

5. Determination of proportion of fine aggregate

Neville, 2011

Comment:

Commonly

20 mm max. size

60-180 mm slump

Page 42 of 62

Volumetric Proportions of Concrete Mass proportions of concrete batching control

Volumetric proportions for consideration of contribution of

components on properties of concrete

Density of concrete = Mc + Mw + Mca + Mfa (M = mass content, kg/m3)

where

c = cement, w = water, ca = coarse aggregate, fa = fine aggregate

Density of components:

Gc, Gw, Gca, Gfa are density of components with


Per cubic metre of concrete, Vcon

Vc, Vw, Vca, Vfa and Vair are volume of components with


Vcon = Vc + Vw + Vca + Vfa + Vair = 1 m3

Vcon = Mc/Gc + Mw/Gw + Mca/Gca + Mfa/Gfa + Vair = 1 m3

(Comment: Entrapped air content 2%, or max. 3% with chemical admixture)

Nominal or determined density to indicate volume supplied in delivery truck

Page 43 of 62

Selection of Ingredient Proportions

Both ACI and DOE approaches do not provide guidance on use of chemical admixtures (use manufacturers recommendation)

The data used are based on experience in temperature climate and temperature effects for tropical climate not included

In most RMC plants, past experience with available constituent materials for concrete has led to typical proportions for common

range of characteristic strengths (C25/30 to C50/60)

As set-retarding and plasticizing admixtures are typically used in tropical climatic conditions, adjustment of consistence is often

provided by adjusting dosage of admixtures

(Water reducing admixture: G1 10%, G2 20% and G3 30% or higher water reduction for similar slump)

Typically strength/water-cement ratio is approximately linear over limited range of values, e.g. Fig. 14.12 (Neville 2011) shows

approx. 10 MPa from w/c = 0.60 to 0.50 and approx. 15 MPa for

each change in w/c = 0.10 between 0.50 and 0.30

Page 44 of 62

Durability Design of Concrete Structures - Sulfate

SS EN 206-1:2009

Clause 4.1 Exposure classes related to

environmental actions

NOTE The exposure classes to be selected

depends on the provisions valid in the place

of use of the concrete.

SS 544-1:2009 Concrete Complimentary Singapore Standard to SS EN 206-1 Part 1: Method of specifying and guidance for the

specifier

Table A.2 Classification of ground

conditions provides more detailed criteria

for sulfate attack

Page 45 of 62


SS 544-1: 2009 (BS 8500-1: 2006)

Page 46 of 62


SS 544-1: 2009 (BS 8500-1: 2006)

Page 47 of 62


SS 544-1: 2009 (BS 8500-1: 2006)

Page 48 of 62

Durability Exposure classes related to environmental influence

Chemical attack (XA classes) BS EN 206-1:

Where concrete is exposed to chemical attack from natural soils and ground water, the exposure shall be classified in Table 2. The classification of sea water depends on the geographical location, therefore the classification valid in the place of use of the concrete applies.

Class

designation

Description of the environment Informative examples where

exposure class may occur

XA1 Slightly aggressive chemical environment

according to Table 2

XA2 Moderately aggressive chemical

environment according to Table 2

XA3 Highly aggressive chemical environment

according to Table 2

Replacement for XA classes in BS EN 206-1, Table (shown above) with BS 8500-1 Annex A (informative) Table A.2 to determine the ACEC-class (see BRE Special Digest 1 for guidance on site investigation)

Refer in BS EN 206-1 Table 2 Limiting values for exposure classes for chemical attack from natural soil and ground water

Page 49 of 62

Extract from Table A.2 of SS 544-1 Classification of ground conditions (refer to the BS 8500-1 for the details)

Sulfate and magnesium Design

sulfate

class

Natural soil Brownfield A) ACEC-

class

(design

sulfate

class)

2:1 water/soil

extract

Groundwater Total

potential

sulfate B)

Static

water

Mobile

water

Static

water

Mobile

water

SO4 Mg C) SO4 Mg

C) SO4

mg/l mg/l mg/l mg/l % pH pH pH D) pH D)

500

to

1500

400

to

1400

0.24 - 0.6 DS-2

> 3.5 AC-1s

> 5.5 >6.5 AC-2

2.5 to 3.5 AC-2s

2.5 to 5.5 5.6 to 6.5 AC-3z

4.5 to 5.5 AC-4z

2.5 to 4.5 AC-5z

1600

to

3000

1500

to

3000

0.7 to 1.2 DS-3

> 3.5 > 5.5 AC-2s

> 5.5 > 6.5 AC-3

2.5 to

3.5

2.5 to 5.5

AC-

3s

2.5 to 5.5 5.6 to 6.5 AC-4

2.5 to 5.5 AC-5 Page 50 of 62

Extract from Table A.9 of SS 544-1 Selection of the nominal cover and DC-class or designated concrete and the number of APM for in-situ concrete elements where the hydraulic gradient due to groundwater is five or less (refer to the BS for details)

ACEC-class Lowest nominal cover E), mm

Intended working lifeF)

At least 50 years G), H)

At least 100 years

AC-1s, AC-1 50I), 75 J) DC-1 (RC25/30 if reinforced)

DC-1 (RC25/30 if reinforced)

AC-2s AC-2 50I), 75 J) DC-2 (FND2) DC-2 (FND2)

AC-2z 50I), 75J) DC-2z (FND2z) DC-2z (FND2z)

AC-3s 50I), 75J) DC-3 (FND3) DC-3 (FND3)

AC-3z 50I), 75J) DC-3z (FND3z) DC-3z (FND3z)

AC-3 50I), 75J) DC-3 (FND3) DC-3 + one APM of choice, FND3 + one APM or choice, DC-4 or FND4

AC-4 50I), 75J) DC-4 (FND4) DC-4 + one APM from APM2 to APM5, or FND4 + one APM from APM2 to APM5

AC-5 50I), 75J) DC-4 (FND4) + APM3 K)

DC-4 (FND4) + APM3K)

I) For concrete cast against binding J) For concrete cast directly against the soil (Designation within brackets refers to Designated Concrete in BS 8500-1)

Page 51 of 62

Extract from Table A.11 of BS 8500-1 Limiting values of composition and properties for concrete where a DC-class is specified

DC-

class

Max.

w/c ratio

Min. cement or combination content

(kg/m3) for max. aggregate size

Cement and

combination types

Grouping used in

BRE SD1:

2005[1]

40 mm 20 mm 14 mm 10 mm

DC-1 A) All in Table A.6 A to G

DC-2

0.55 300 320 340 360 IIB-V+SR, IIIA+SR,

IIIB+SR, IVB-V

D, E, F

0.50 320 340 360 380 CEM I, SRPC, IIA-D,

IIA-Q, IIA-S, IIA-V, IIB-

S, IIB-V, IIIA, IIIB

A, G

0.45 340 360 380 380 IIA-L or LL 42.5 B

0.40 360 380 380 380 IIA-L or LL 32.5 C

DC-2z 0.55 300 320 340 360 All in Table A.6 A to G

DC-3

0.50 320 340 360 380 IIIB+SR F

0.45 340 360 380 380 IVB-V E

0.40 360 380 380 380 IIB-V+SR, IIIA+SR,

SRPC

D, G

DC-3z 0.50 320 340 360 380 All in Table A.6 A to G

A) If the concrete is reinforced or contains embedded metal, the minimum concrete quality for 20 mm maximum aggregate

size is C25/30, 0.65, 260 or designated concrete RC25/30.

Page 52 of 62

Exposure Classes

Page 53 of 62

Exposure Classes

National Foreword to SS 544-1: 2009

Guidelines are highlighted to guide local

users:

Annex A (informative) Exposure classes related to environmental conditions

In order to cater to the higher ambient

temperatures in Singapore compared to

UK, the recommendation is to consider

the required concrete for at least one

class higher than that based on exposure

conditions in accordance with the

requirements for UK exposure conditions

(refer to Table A.3).

The specifier should take into

consideration the nature of the element,

intended working life, its importance and

the cost of maintenance and repair to

select the same or higher performance

concrete.

Different elements in the same structure

may be specified with different concrete

to optimise cost-effectiveness. Page 54 of 62

SS EN 544-1: 2009 Annex A (informative)

Page 55 of 62


Page 56 of 62


Page 57 of 62


Page 58 of 62

Durability Design of Concrete Structures - Examples

Example Prescribed limits on w/c, cement content and cement type

Exposure class: Corrosion induced by carbonation (XC classes)

Concrete for

nominal cover

of 25+c (mm)

Exposure class: XC3/4: (intended working life of at least 50 years, 20 mm

maximum size aggregate) Cement type: All in Table 6, except IVB-V

Strength class SS 544-1 Table A.4 With + 2 MPa With + 5 MPa

Designation C30/37-XC3/4 (0.55 300) C32/40-XC3/4 (0.52 310) C35/45-XC3/4 (0.50 320)

Comment UK conditions May not be adequate Preferred

Increase

nominal cover

to 30+c (mm)





Comment UK conditions May not be adequate Preferred

Concrete for

nominal cover

of 30+c (mm)





Comment UK conditions Preferred For off-form finish Page 59 of 62

Durability Design of Concrete Structures - Examples

Example Prescribed limits on w/c, cement content and cement type

Exposure class: Corrosion induced by carbonation (XC classes)

Concrete for

nominal cover

of 25+c (mm)

Exposure class: XC2: (intended working life of at least 50 years, 20 mm

maximum size aggregate) Cement type: All in Table 6


Designation C25/30-XC2 (0.65 260) C28/30-XC2 (0.60 280) C30/37-XC2 (0.55 300)

Comment UK conditions, same

for higher covers

May not be adequate Preferred

Concrete for

nominal cover

of 30+c (mm)

Exposure class : XC2: (intended working life of at least 100 years, 20 mm

maximum size aggregate) Cement type: All in Table 6


Designation C25/30-XC2 (0.65 260) C28/30-XC2 (0.60 280) C30/37-XC2 (0.55 300)

Comment As for 50 years, but

with larger cover

May not be adequate Preferred

Note:

XC2: for foundations, often with nominal cover of 50 mm

XC3/XC4: for above ground structures (see also XS1 airborne salts) Page 60 of 62

Comparison of Approach Information provided:

Characteristic strength = C40/50 (target 48/60 MPa)

Coarse aggregate: Dry-rodded density = 1650 kg/m3

S.G. (SSD) = 2.65, Absorption 1%, Effective absorption = 0.5%

Fine aggregate: Free moisture content 8% (total 9.5% absorption 1.5%)

S.G. (SSD) = 2.50

Fineness modulus = 2.60, % passing 600 m = 50%

CEM I (ASTM Type 1), S.G. = 3.15

Durability: XO (no special requirement)

(a) Select concrete composition without admixture (SSD aggregates)

(b) Select concrete composition with admixture (SSD aggregates)

Admixture to be taken as part of added water (dosage < 2 kg/m3)

Water reduction = 15% when added at recommended dosage

Compute batch quantities for 1m3 in each case (adjusted for moisture)

Comment on differences in composition between ACI and DOE methods

Page 61 of 62

Review of Results

Each method is based on different approaches to the selection of values

to arrive at the concrete composition.

The results may differ within a narrow range between different persons

as interpolation may be needed using the tables and figures provided

in the presentation

You are encouraged to carry out case (a) for both approaches and send

their compositions by e-mail to [email protected]

A summary of submitted results will be presented for review at the end

of the next presentation

Adjust concrete composition if Initial Test show:

(Each case taken separately, all others data remain as before)

(a) Mean cube compressive strength is 5 MPa below target

(b) Fineness modulus changed to 2.30 (% passing 600 m = 60%)

(c) Fine aggregate total moisture content = 12%

Page 62 of 62

8. selection of concrete composition

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