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Page 1: Exercise 7 - Aalto · MIX DESIGN OF HIGH STRENGTH CONCRETE, SPECIAL CASES IN MIX DESIGN Exercise 7 Introduction ... m = the target mean strength f

MIX DESIGN OF HIGH STRENGTHCONCRETE, SPECIAL CASES IN

MIX DESIGN

Exercise 7

Introduction

• The strength of high strength concretes is K70 – K100(By50).

• Ultra high strength concrete (RPC aka Reactive PowderConcrete) contains:– rock powder as aggregate– with steel dust and steel fibres which compact the concrete

so that it can reach strengths of up to 800 MPa.

• Low water/cement ratio: below 0,35 even below 0,20

Page 2: Exercise 7 - Aalto · MIX DESIGN OF HIGH STRENGTH CONCRETE, SPECIAL CASES IN MIX DESIGN Exercise 7 Introduction ... m = the target mean strength f

Introduction• High strength concretes are composed of same

materials as normal strength concretes.• the selection of cement and additives is based on:

– The desired strength gain and– heat development

• The used aggregate contains only small amounts offines and silt. Due to the high amount of binder andthat the aggregate grading does not have as biginfluence as in normal strength concrete.

• Requires the use of water reducing admixtures(superplasticizers)

• Requires careful curing

Mix design of High Strength Concrete1. Define proportioning strength of concrete2. Define the amount of binder and Calculate the amount

of cement and additional binders3. Define the amount of (super)plasticizer4. Define the amount of water5. Calculate the amount of aggregate with the volumetric

equation of concrete6. Combine the aggregate7. Define the components of the batch and make a trial

batch

Page 3: Exercise 7 - Aalto · MIX DESIGN OF HIGH STRENGTH CONCRETE, SPECIAL CASES IN MIX DESIGN Exercise 7 Introduction ... m = the target mean strength f

1. Define proportioning strength of concretefm = fc + ksfm = the target mean strengthfc = the specified characteristic strengths = the standard deviation, andk = a constant

The constant k is derived fromthe mathematics of the normaldistribution and increases asthe proportion of defectives isdecreased, thus:

k for 10% defectives = 1.28k for 5% defectives = 1.64k for 2.5% defectives = 1.96k for 1% defectives = 2.33

BRE - Building Research Establishment, UKDesign of normal concrete mixeshttp://www.cmse.ed.ac.uk/MSE3/Cement/2ED3575-CIS888614800250940.pdf

1. Define proportioning strength of concrete• It is generally accepted

that at a given level ofcontrol the standarddeviation increases as thespecified characteristicstrength increases up to aparticular level

• the standard deviationbeing independent of thespecified characteristicstrength above 20N/mm2.

BRE - Building Research Establishment, UKDesign of normal concrete mixeshttp://www.cmse.ed.ac.uk/MSE3/Cement/2ED3575-CIS888614800250940.pdf

Page 4: Exercise 7 - Aalto · MIX DESIGN OF HIGH STRENGTH CONCRETE, SPECIAL CASES IN MIX DESIGN Exercise 7 Introduction ... m = the target mean strength f

2. Define the amount of binder and calculate theamount of cement and additional binders

C = cementSi = Silica fumeLt = Fly ashMk = Blastfurnace slag

From the report: ”Korkealujuuksisten betonien suhteitus”; Penttala V. et. al. (1990).

Binder amount (C+2,5·Si+0,3·Lt+Mk)- use the mineral admixtures proportion of the cement to

calculate the amount of cement, silica, fly ash andblast furnace slag

3. Define the amount of (super)plasticizer

From the report: ”Korkealujuuksisten betonien suhteitus”; Penttala V. et. al. (1990).

The amount of plastizer as proportion of the binder isdefined based on the target mean strength (proportioningstrength)

Page 5: Exercise 7 - Aalto · MIX DESIGN OF HIGH STRENGTH CONCRETE, SPECIAL CASES IN MIX DESIGN Exercise 7 Introduction ... m = the target mean strength f

4. Define the amount of water• Curves determine the (water-

admixture – air / binder) ratioof high strength concrete

• The proportioning strength isK28

• The compressive strength isdetermined using 100 mmcubes

• The amount of air is assumedto be 10 dm3/m3

• Amount of admixture fromSTEP 3 From the report: ”Korkealujuuksisten betonien suhteitus”; Penttala V. et. al. (1990).

5. Calculate the amount of aggregate

• Calculate the amount ofaggregate with the volumetricequation of concrete.

• The amount of air is assumed tobe 10 dm3/m3

C = cementSi = Silica fumeLt = Fly ashMk =Blastfurnace slagI = air contentNt = PlasticizerW = WaterR = Aggregates

Page 6: Exercise 7 - Aalto · MIX DESIGN OF HIGH STRENGTH CONCRETE, SPECIAL CASES IN MIX DESIGN Exercise 7 Introduction ... m = the target mean strength f

6. Combine the aggregate

7. Define the components of the batch and make a trialbatch

Page 7: Exercise 7 - Aalto · MIX DESIGN OF HIGH STRENGTH CONCRETE, SPECIAL CASES IN MIX DESIGN Exercise 7 Introduction ... m = the target mean strength f

the mix design process

• The guidelines of the mix design are drawn upfor 100*100*100 mm cubes

• Binders:– Cement kcem 1– Blast furnace slag kMK 1– Fly ash kLT 0,3– Silica ksil 2,5

• The mix design guidelines are for concretes ofconsistency 2-3 sVB (≈ S3/S2)

Page 8: Exercise 7 - Aalto · MIX DESIGN OF HIGH STRENGTH CONCRETE, SPECIAL CASES IN MIX DESIGN Exercise 7 Introduction ... m = the target mean strength f

Exersice 1Proportion a K100 concrete (at the age of 28days) with CEM I as binder with 8 % silica fume.

INPUT:K28 = 100 MPaCement type = CEM ISilica amount = 0,08 * cement [kg/m³]

1) Proportioning strength

fm = fc + ksfc = 100 MPak for 10% defectives = 1.28s for 100MPa and less than 30 samples = 8 MPafm = 100 + 1.26*8 =Ø fm = 110MPa

Page 9: Exercise 7 - Aalto · MIX DESIGN OF HIGH STRENGTH CONCRETE, SPECIAL CASES IN MIX DESIGN Exercise 7 Introduction ... m = the target mean strength f

Amount of binder is 630 kg/m3

2) Define the amount of binder

2. Calculate the amounts of cement andadditional binders

• from the binder amount (in this case theamounts of cement and silica).

Binder amount (C+2,5·Si+0,3·Lt+Mk)Si = 8% cement, Lt and MK = 0%C+2,5·0,08C = 630C(1+0,2) = 630C = 525 kg/m3 and Si = 42 kg/m3

Page 10: Exercise 7 - Aalto · MIX DESIGN OF HIGH STRENGTH CONCRETE, SPECIAL CASES IN MIX DESIGN Exercise 7 Introduction ... m = the target mean strength f

Amount of plasticizer is 3,3 % (C+Si)0,033*(525+42) = 18,7 kg/m3

3) Define the amount of (super) plasticizer

Lt and MK = 0%

4) Define the water amount

We get

(W+Nt+I)/S = 0,25

(W+Nt+I)/(C+2,5*Si) = 0,25

(W+18,7+10)/(525+2,5*42)

→ W = 0,25(630) – 18,7 – 10

→ W = 128,8 kg/m3

Binder amount(C+2,5·Si+0,3·Lt+Mk)

Page 11: Exercise 7 - Aalto · MIX DESIGN OF HIGH STRENGTH CONCRETE, SPECIAL CASES IN MIX DESIGN Exercise 7 Introduction ... m = the target mean strength f

5) Calculate the amount of aggregate

+ W + N + Air + + + + =1000

Thus,

,+ 128,8 + 18,7 + 10 +

,+

,= 1000

QAGG = (1000 – 128,8 – 18,7 – 10 – 169,4 – 19,1) * 2,68

QAGG = 654 dm3 = 1753 kg/m3

Ex 1 - Mix designingredient kg/m³

Cement 525

Silica fume 42

Fly ash --

GGBS --

Water 128,8

Superplasticizer 18,7

Aggregates 1753

W/C = 0,25W/B = 0,23

Page 12: Exercise 7 - Aalto · MIX DESIGN OF HIGH STRENGTH CONCRETE, SPECIAL CASES IN MIX DESIGN Exercise 7 Introduction ... m = the target mean strength f

Exersice 2Proportion concrete for which the referencestrength for 150 mm cubes is 55 MPa at the ageof 1 day. As binder use CEMI, 10 % silica fumeand 30 % fly ash.INPUT:K28 = ????Cement type = CEM ISilica amount = 0,10 * cement [kg/m³]Fly ash amount = 0,30 * cement [kg/m³]

1) Proportioning strength• The guidelines of the mix design are drawn up for

100*100*100 mm cubes.• For 100 mm cubes the compressive strengths are

about 5 % greater than for 150 cubes• For 100 mm cubes the compressive strengths should

thus be fm = 55*1,05 = 58 MPa• The standard deviations of the strength of the 100

mm cubes are higher than that of the 150 mm cubes.• The mean standard deviation of the strength of the

150 mm cubes are about 4 MPa• fm = 58 + 1.26*4 = 63 MPaà 1d strength

Page 13: Exercise 7 - Aalto · MIX DESIGN OF HIGH STRENGTH CONCRETE, SPECIAL CASES IN MIX DESIGN Exercise 7 Introduction ... m = the target mean strength f

The compressive strength at28 days

fs at the age of 28 days is 85MPa

1) Proportioning strength

Amount of binder is 440 kg/m3

2) The amount of binder from figure

Page 14: Exercise 7 - Aalto · MIX DESIGN OF HIGH STRENGTH CONCRETE, SPECIAL CASES IN MIX DESIGN Exercise 7 Introduction ... m = the target mean strength f

INPUT: Silica amount = 0,10 * cement [kg/m³]Fly ash amount = 0,30 * cement [kg/m³]

The amount of binder (C + 2,5Si + 0,3Lt) = 440Si = 0,1C Lt = 0,3CC (1 + 2,5*0,1 + 0,3*0,3) = 440C = 328,4 kg/m3 Si = 32,8 kg/m3 Lt = 98,5 kg/m3

2) The amount of binder

Amount of plasticizer 2,8 %0,028*(328,4 + 32,8 + 98,5) = 12,9 kg/m3

3) define the amount of plasticizer

Page 15: Exercise 7 - Aalto · MIX DESIGN OF HIGH STRENGTH CONCRETE, SPECIAL CASES IN MIX DESIGN Exercise 7 Introduction ... m = the target mean strength f

4) Define the water amount

We get:

(W+Nt+I)/S = 0,39

(W+12,9+10)/(440) = 0,39

→ W = 0,39(440) – 12,9 – 10

→ W = 148,7 kg/m3

5) Calculate the amount of aggregate

+ W + N + I + + + + = 1000

Thus,

,+ 148,7 + 12,9 + 10 + ,

,+ ,

,+ ,

,= 1000

QAGG = (1000 – 148,7 – 12,9 – 10 – 105,9 – 14,9 – 42,8) * 2,68QAGG = 664,8 *2,68 = 1782 kg/m3

Page 16: Exercise 7 - Aalto · MIX DESIGN OF HIGH STRENGTH CONCRETE, SPECIAL CASES IN MIX DESIGN Exercise 7 Introduction ... m = the target mean strength f

Ex 2 - Mix designingredient kg/m³

Cement 328.4

Silica fume 32.8

Fly ash 98.5

GGBS --

Water 148.7

Superplasticizer 12.9

Aggregates 1782

W/C = 0,45W/B = 0,34

Exersice 3How would you change the mix design if themeasured consistency of the concrete was 4 sVBand the 1st day strength was 58 MPa?INPUT:K28 = ????Consistency = 4 sVBCement type = CEM ISilica amount = 0,10 * cement [kg/m³]Fly ash amount = 0,30 * cement [kg/m³]

Page 17: Exercise 7 - Aalto · MIX DESIGN OF HIGH STRENGTH CONCRETE, SPECIAL CASES IN MIX DESIGN Exercise 7 Introduction ... m = the target mean strength f

1) Proportioning strength• For 100 mm cubes the compressive strengths are

about 5 % greater than for 150 cubes• fm = 58*1,05 = 61 MPa• The mean standard deviation of the strength of the

150 mm cubes are about 4 MPa• fm = 61 + 1.26*4 = 66 MPaà 1d strength

From the chart, we cannotice that:• 1 day fs = 66 Mpa• fs at the age of 28 days is

90 MPa

1) Proportioning strength

Page 18: Exercise 7 - Aalto · MIX DESIGN OF HIGH STRENGTH CONCRETE, SPECIAL CASES IN MIX DESIGN Exercise 7 Introduction ... m = the target mean strength f

New amount of binder is 460 kg/m3

2) The amount of binder

INPUT: Silica amount = 0,10 * cement [kg/m³]Fly ash amount = 0,30 * cement [kg/m³]

The amount of binder (C + 2,5Si + 0,3Lt) = 460Si = 0,1C Lt = 0,3CC (1 + 2,5*0,1 + 0,3*0,3) = 460C = 343,3 kg/m3 Si = 34,3 kg/m3 Lt = 103 kg/m3

2) The amount of binder

Page 19: Exercise 7 - Aalto · MIX DESIGN OF HIGH STRENGTH CONCRETE, SPECIAL CASES IN MIX DESIGN Exercise 7 Introduction ... m = the target mean strength f

3) amount of plasticizer

BY 15(old)

BY 50(new)

New plasticizer amount is 3,0 % but because the previousconcrete mix was too stiff, we´ll raise the amount of plasticizerto 3,2 %0,032*(480,6) = 15,4 kg/m3

3) amount of plasticizer

Page 20: Exercise 7 - Aalto · MIX DESIGN OF HIGH STRENGTH CONCRETE, SPECIAL CASES IN MIX DESIGN Exercise 7 Introduction ... m = the target mean strength f

4) water amount :

(W+Nt+I)/S = 0,35

(W+15,4+10)/(460) = 0,35

→ W = 0,35(460) – 15,4 – 10

→ W = 135,6 kg/m3

4) Calculate the amount of aggregate

+ W + N + I + + + + = 1000

Thus,

,+ 135,6 + 15,4 + 10 + ,

,+ ,

,+

,= 1000

QAGG = (1000 – 135,6 – 15,4 – 10 – 110,7 – 15,6 – 44,8) * 2,68QAGG = 667,9 *2,68 = 1790 kg/m3

C = 343,3 kg/m3 Si = 34,3 kg/m3 Lt = 103 kg/m3

Page 21: Exercise 7 - Aalto · MIX DESIGN OF HIGH STRENGTH CONCRETE, SPECIAL CASES IN MIX DESIGN Exercise 7 Introduction ... m = the target mean strength f

Ex 3 - Mix designingredient kg/m³

Cement 343.3

Silica fume 34.3

Fly ash 103

GGBS --

Water 135.6

Superplasticizer 15.4

Aggregates 1790

W/C = 0,39W/B = 0,29

Exersice 4• Which matters should be taken into

consideration when proportioning pumpableconcrete?

• How about concrete with high wear resistance(kulutuskestävyys)?

Page 22: Exercise 7 - Aalto · MIX DESIGN OF HIGH STRENGTH CONCRETE, SPECIAL CASES IN MIX DESIGN Exercise 7 Introduction ... m = the target mean strength f

Pumpable concrete• The grading of the aggregate should be

continuous– Bleeding is usually a result of non-continuous grading

or coarse sand which causes discontinuity betweenthe finest material.

• Sufficient amount of fine material (cement,additional binders, filler), using of crushedaggregate increases the needed amount of fines.– Cement 240 - 400 kg/m3

– Amount of fines <0,25 mm: 350 - 500 kg/m3

http://canusaequipment.com/wp-content/canusamedia/PUMPABLE%20CONCRETE%20INFO-PDF.pdf

• Consistency S4 – S2 (S1)• Use of plasticizers improves pumpability• Air entraining agents may hinder it• The amount of air is decreased during

pumping• The maximum size of aggregate

– 1/3 of the size of the distributing pipe

Page 23: Exercise 7 - Aalto · MIX DESIGN OF HIGH STRENGTH CONCRETE, SPECIAL CASES IN MIX DESIGN Exercise 7 Introduction ... m = the target mean strength f

High abrasion (wear) resistance• Abrasion damage occurs when the surface of concrete is

unable to resist wear caused by rubbing and friction.

• As the outer paste of concrete wears, the fine and coarseaggregate are exposed and abrasion and impact will causeadditional degradation that is related to aggregate-to-pastebond strength and hardness of the aggregate.

• Although wind-borne particles can cause abrasion ofconcrete, the two most damaging forms of abrasion occur onvehicular traffic surfaces and in hydraulic structures, such asdams, spillways, and tunnels.

High abrasion (wear) resistance• The hardened cement paste is the weakest

link, the aggregate the most durable• The aim is to use as much aggregate as

possible• Lower the amount of material passing the

sieves 0,125mm and 4mm• Avoid too plastic concrete compositions• Use of plasticizers• Sufficient strength


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