beton mutu tinggi pertemuan 11 matakuliah: s0793 – teknologi bahan konstruksi tahun: 2009

BETON MUTU TINGGIPertemuan 11

Matakuliah : S0793 – Teknologi Bahan KonstruksiTahun : 2009

Bina Nusantara University 3

Learning Outcome

• Mahasiswa dapat menjelaskan persyaratan dan tata cara pembuatan beton mutu tinggi


Outline Materi

• Defenisi Beton Mutu Tinggi• Aplikasi Beton Mutu Tinggi• Persyaratan Bahan Beton Mutu Tinggi• Cara Pembuatan Beton Mutu Tinggi


High Performance Concrete

Concrete may be regarded as high performance for several different reasons:

• high strength, • high workability • high durability – and perhaps also improved visual appearance.


High Performance Concrete

• High strength concrete (HSC) might be regarded as concrete with a strength in excess of 60MPa and such concrete can be produced as relatively normal concrete with a higher cement content and a normal water-reducing admixture.

• However ultra high performance concrete (UHPC) will more usually contain cement replacement materials and a high-range water-reducer (HRWR) or superplasticiser(SP) (different names for the same thing).


Ultra High Strength Concrete

• How High?• Strengths of 150-200MPa were reported in

several papers at a recent symposium• How is it done?• Using only fine sand as an aggregate, a high

content of cement and silica fume, a high dosage of HRWR admixture plus steel fibres


Ultra High Strength Concrete

• In what kind of structures?• Thin shell roofing (2cm thick) and “bulb” double

and single tees were reported• Both insitu and precast applications• Flexural and tensile strengths also high,

allowing omission of secondary reinft.• Concrete in tees was generally self- compacting


Overview

• What is High Performance Concrete?

• International use of HPC in bridges

• Use of HPC in Australia

• Economics of High Strength Concrete

• HSC in AS 5100 and DR 05252

• Case Studies

• Future developments

• Recommendations


What is High Performance Concrete?

"A high performance concrete is a concrete in which certain characteristics are developed for a particular application and environments:

• Ease of placement• Compaction without segregation• Early-age strength• Long term mechanical properties• Permeability• Durability• Heat of hydration• Toughness• Volume stability• Long life in severe environments


Information on H.P.C.

“Bridge Views” – http://www.cement.org/bridges/br_newsletter.asp

“High-Performance Concretes, a State-of-Art Report (1989-1994)”

- http://www.tfhrc.gov/structur/hpc/hpc2/contnt.htm

“A State-of-the-Art Review of High Performance Concrete Structures Built in Canada: 1990-2000” - http://www.cement.org/bridges/SOA_HPC.pdf

“Building a New Generation of Bridges: A Strategic Perspective for the Nation” -

http://www.cement.org/hp/


International Use of H.P.C.

• Used for particular applications for well over 20 years.

• First international conference in Norway in 1987

• Early developments in Northern Europe; longer span bridges and high rise buildings.

• More general use became mandatory in some countries in the 1990’s.

• Actively promoted for short to medium span bridges in N America over the last 10 years.



• Scandinavia

• Norway– Climatic conditions, long coastline, N. Sea oil– HPC mandatory since 1989– Widespread use of lightweight concrete

• Denmark/Sweden– Great Belt project– Focus on specified requirements

• France• Use of HPC back to 1983• Useage mainly in bridges rather than buildings• Joint government/industry group, BHP 2000• 70-80 MPa concrete now common in France



• North America

• HPC history over 30 years• Use of HPC in bridges actively encouraged by owner

organisation/industry group partnerships.• “Lead State” programme, 1996.• HPC “Bridge Views” newsletter.• Canadian “Centres of Excellence” Programme, 1990• “A State-of-the-Art Review of High Performance

Concrete Structures Built in Canada: 1990-2000”


Use of H.P.C. in Australia

• Maximum concrete strength limited to 50 MPa until the introduction of AS 5100.

• Use of HPC in bridges mainly limited to structures in particularly aggressive environments.

• AS 5100 raised maximum strength to 65 MPa

• Recently released draft revision to AS 3600 covers concrete up to 100 MPa

INDONESIA?


Economics of High Strength Concrete

0.6 in diameter strands 0.5 in diameter strandsSpacing, m 3.4 2.7 2.1 1.5 3.4 2.7 2.1 1.5

SectionAAASHTO 90 83 83 83 76 76 69 69

Type IAAASHTO 90 90 90 83 76 76 76 76

Type IIAAASHTO 83 83 83 76 76 69 69 62

Type IIIAAASHTO 83 83 83 83 62 62 62 62

Type IVNU1100 83 76 76 76 62 62 62 62

NU1350 83 76 69 69 62 62 62 55

Table 1 Maximum effective girder compressive strength, after Kahn and Saber (34)



• Compressive strength at transfer the most significant property, allowable tension at service minor impact.

• Maximum spans increased up to 45 percent• Use of 15.2 mm strand for higher strengths.• Strength of the composite deck had little impact.• HSC allowed longer spans, fewer girder lines, or

shallower sections.• Maximum useful strengths:

• I girders with 12.7 mm strand - 69 MPa• I girders with 15.2 mm strand - 83 MPa• U girders with 15.2 mm strand - 97 MPa


AS 5100 Provisions for HSC

• Maximum compressive strength; 65 MPa

• Cl. 1.5.1 - Alternative materials permitted

• Cl 2.5.2 - 18 MPa fatigue limit on compressive stress - conservative for HSC

• Cl 6.11 - Part 2 - Deflection limits may become critical

• Cl 6.1.1 - Tensile strength - may be derived from tests

• Cl 6.1.7, 6.1.8 - Creep and shrinkage provisions conservative for HSC, but may be derived from test.


AS 5100 and DR 05252Subject

AS 5100 DR 05252 AS 5100 DR 052521.1.2 1.1.2 Concrete srength and

density range25-65 MPa, 2100-2800 kg/m3 20-100 MPa, 1800-2800 kg/m3

1.5.1 - Use of alternative materials Alternatives allowed Clause removed

2.2 2.2 Strength reduction factors Phi reduced for ku > 0.4 Phi reduced for ku > 0.375

2.5.2 - Fatigue provisions Maximum stress under fatigue loading = 18 MPa

Not included

6.1.1(b,c)

3.1.1.2(b) Tensile strength From compressive strength or tests From flexural or tensile tests, upper and lower bound factors applied if compressive strength used

6.1.2 3.1.2 Modulus of elasticity Proportional to square root fc Revised for higher strength grades6.1.7 3.1.7 Shrinkage Default basic shrinkage strain

independent of concrete strengthAutogeneous and drying shrinkage calculated separately, both related to concrete strength

6.1.8 3.1.8 Creep Basic creep factor constant for f'c >= 50 MPa

Basic creep factor increased for f'c = 40, 50 MPa; reduced for f'c >= 80 MPa

6.4.3.3 3.4.3.3 Loss of prestress due to creep

Default creep factor uses prestress force before time-dependent losses.

Default creep factor reduced to 80% of AS 5100 value

8.1.2.2 8.1.3 Rectangular stress block Stress = 0.85f'c Stress = (1.0-0.003f'c)f'c with limits of 0.67 and 0.85

8.2.7.1 8.2.7.1 Shear strength of beams excluding shear reinforcement

Shear strength proportional to f'c1/3 f'c

1/3 limited to 4 Mpa, ie no increase in shear strength for f'c > 64 MPa

8.2.8 8.2.8 Minimum shear reinforcement

Independent of concrete strength Increased area for f'c > 36 MPa

8.6.1(a) 8.6.1(a) Minimum steel area in tensile zone

3ks(Act/fs) Cl 8.1.4.1 (minimum strength requirements) applied

9.1.1 9.1.1 Minimum tensile steel in slabs

Independent of concrete strength Increased area for f'c > 30 MPa approx

Clause Provisions


AS 5100 and DR 05252

Main Changes:• Changes to the concrete stress block parameters for

ultimate moment capacity to allow for higher strength grades.

More detailed calculation of shrinkage and creep deformations, allowing advantage to be taken of the better performance of higher strength concrete

Shear strength of concrete capped at Grade 65.

Minimum reinforcement requirements revised for higher strength grades.

Over-conservative requirement for minimum steel area in tensile zones removed.


Case Studies

• Concrete strength: 50 MPa to 100 MPa

• Maximum spans for typical 3 lane Super-T girder bridge with M1600 loading

• Standard Type 1 to Type 5 girders

• Type 4 girder modified to allow higher pre-stress force:

Increase bottom flange width by 200 mm (Type 4A)

Increase bottom flange depth by 50 mm (Type 4B)

Increase bottom flange depth by 100 mm (Type 4C)


Case Studies

Compressive strength at transfer = 0.7f’c.

Steam curing applied (hence strand relaxation applied at time of transfer)

Strand stressed to 80% specified tensile strength.

Creep, shrinkage, and temperature stresses in accordance with AS 5100.

In-situ concrete 40 MPa, 160 mm thick in all cases.

Assumed girder spacing = 2.7 m.


Case Studies

Type Depth Max NoStrands

A I Yc A I Ycmm mm2 mm4 mm mm2 mm4 mm

1 750 454,084 3.280E+10 389 887,584 7.685E+10 604 502 1000 491,409 6.675E+10 515 924,909 1.412E+11 779 503 1200 531,021 1.043E+11 613 964,521 2.112E+11 913 504 1500 573,592 1.756E+11 776 1,007,092 3.357E+11 1,122 505 1800 616,426 2.658E+11 946 1,049,926 4.886E+11 1,331 50

4A 1500 680,172 1.971E+11 627 1,113,672 4.383E+11 998 824B 1500 592,772 1.798E+11 760 1,026,272 3.488E+11 1,106 624C 1500 618,612 1.840E+11 743 1,052,112 3.632E+11 1,088 74

Section PropertiesPrecast Composite


Super-T Maximum Span

25

30

35

40

45

50

55

18.00 20.00 22.00 24.00 26.00 28.00 30.00 32.00 34.00 36.00 38.00

Maximum Span, m

Nu

mb

er

of

Str

an

ds

Type 1

Type 2

Type 3

Type 4

Type 5

50 MPa

65 MPa

80 MPa


Super-T Maximum Span

45

50

55

60

65

70

75

80

85

33 34 35 36 37 38 39 40

Maximum Span, m

Nu

mb

er

of

Str

an

ds

Type 4

Type 4A

Type 4B

Type 4C

50 MPa

65 MPa

80 MPa


Case Studies - Summary

Significant savings in concrete quantities and/or construction depth.

• Grade 65 concrete with standard girders.

• Grade 80 concrete with modified girders and Type 1 and 2 standard girders.

• More substantial changes to beam cross section and method of construction required for effective use of Grade 100 concrete.


Future Developments

• Strength-weight ratio becomes comparable to steel:

0

5

10

15

20

25

30

35

40

45

Structural steel Concrete High strengthconcrete

Lightweight HSC

Strength-Weight Ratio


Future Developments


Summary

Clear correlation between government/industry initiatives and useage of HPC in the bridge market.

• Improved durability the original motivation for HPC use.

• Studies show direct economic benefits.

• HPC usage in Australia limited by code restrictions.


Recommendations

65 MPa to be considered the standard concrete grade for use in precast pre-tensioned bridge girders and post tensioned bridge decks.

The use of 80-100 MPa concrete to be considered where significant benefit can be shown.

AS 5100 to be revised to allow strength grades up to 100 MPa as soon as possible.

Optimisation of standard Super-T bridge girders for higher strength grades to be investigated.

Investigation of higher strength grades for bridge deck slabs, using membrane action to achieve greater spans and/or reduced slab depth.


Recommendations

Active promotion of the use of high performance concrete by government and industry bodies:

– Review of international best practice

– Review and revision of specifications and standards

– Education of designers, precasters and contractors

– Collect and share experience


Pembuatan Beton Mutu Tinggi

• Faktor yang perlu diperhatikan:– Faktor Air Semen (semakin rendah, kekuatan beton

semakin tinggi menyebabkan kesulitan pada pengerjaan).

– Kualitas Agregat Halus (agregat berbentuk bulat mempunyai rongga udara minimum 33% lebih kecil dari rongga udara yang dipunyai agregat berbentuk lainnya)

– Kualitas Agregat Kasar (pemilihan agregat kasar dengan porositas rendah, butir maksimum, gradasi yang baik)

– Bahan tambahan (water reducing, super fly ash)– Kontrol kualitas (pengambilan sample, pengujian, proses

penakaran)

beton mutu tinggi pertemuan 11 matakuliah: s0793 – teknologi bahan konstruksi tahun: 2009

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