JCI-RILEM International Workshop, CONCRACK5, April 24-26, 2017, Japan 1

PROVISIONS AGAINST THERMAL AND DRYING SHRINKAGE CRACKING IN CONSTRUCTION OF PRESTRESSED

CONCRETE BRIDGE

K. Koroyasu

N. Kiyotaka

S. Nojima

Shimizu Corporation, JAPAN

Shimizu Corporation, JAPAN

Central Nippon Expressway, JAPAN

JCI-RILEM International Workshop, CONCRACK5, April 24-26, 2017, Japan 2

AGENDA

1.Introduction & Summary of Construction

2.Provisions for Thermal Cracking

3. ( Provisions for Drying Shrinkage Cracking )

4.Conclusions

JCI-RILEM International Workshop, CONCRACK5, April 24-26, 2017, Japan 3

Prestressed concrete bridge

In winter, the lowest temperature < 0°C

During the in-service period, the de-icing agent is planed to be used.

If the concrete structure has some cracks, the accelerated concrete deterioration becomes an issue.

Technical challenges was to control the early age cracking.

Introduction & Summary of Construction

JCI-RILEM International Workshop, CONCRACK5, April 24-26, 2017, Japan 4

Construction Outline

[Unit: m]

Type: 5 and 9 span of continuous PC box-girder bridgesErection method: Cantilever, Fixed falsework

Introduction & Summary of Construction

JCI-RILEM International Workshop, CONCRACK5, April 24-26, 2017, Japan 5

Side Closure

6.473

Cantilever

35.000

Column Carital

12.000

Cantilever

35.000

Closure

2.962

3.500

Cantilever Erection

Typical longitudinal section

Typical cross sections2.0252.325 3.0502.850

5.500

10.250 10.250

2.2252.325 2.8502.850In the Spans

Introduction & Summary of Construction

Column Capital

JCI-RILEM International Workshop, CONCRACK5, April 24-26, 2017, Japan 6

Introduction & Summary of Construction

This report explains the controlling methodsof the early age cracking that had beenadopted for the bridge construction of thecantilever erection.

Contents of this report

The early age cracking: Thermal cracking ( and Drying shrinkage cracking )

JCI-RILEM International Workshop, CONCRACK5, April 24-26, 2017, Japan 7

Requirements and Constraints

Targets of Thermal Crack Control(Minimum Limit Values of Thermal Cracking Index)

3D-FE Analysis for Initial Construction

Verification(Satisfy the Limit Values?)

Yes

Consideration of Additional Provisions

No

Standard Construction Methods and Material

Construction

First

Provisions for Thermal CrackingObjective

Flow diagram of verification (Ordinary)

Additional verification

JCI-RILEM International Workshop, CONCRACK5, April 24-26, 2017, Japan 8

Verification(Satisfy the Limit Values?)

Yes

Consideration of Additional Provisions

Confirmation of Each Matter Value for Property

No

First Construction

Thermal Fitting Analysis

3D-FE Analysis for the Following Constructions

Verification(Satisfy the Limit Values?)

Yes

Consideration of Additional Provisions

No

Remaining Constructions to Follow

Measurement of Concrete Temperature

Provisions for Thermal CrackingObjective

Flow diagram of verification (This Construction)

Additional verification

JCI-RILEM International Workshop, CONCRACK5, April 24-26, 2017, Japan 9

Objective

Provisions for Thermal Cracking

PartMinimum

limit values ofcracking index

Rough indication ofcracking index in [1]

Upper slab,Bridge end 1.75

When thermal cracking is required to be prevented

(Thermal cracking probability: 5%)

Under slab,Web 1.45

When thermal cracking is required to be limited as much as possible

(Thermal cracking probability: 25%)

Target values of thermal cracking index

[1]: Standard Specification for Concrete Structures -2007

JCI-RILEM International Workshop, CONCRACK5, April 24-26, 2017, Japan 10

Part Change of cement type

Expansive additive

Insulated curing

Concrete cooling

Column capital

1st lift ○ ○ ○

2nd lift ○ ○

Cantilever ○ ○

Closure ○ ○ ○

Side closure

1st lift ○ ○

2nd lift ○ ○ ○

List of provisions against thermal cracking

Provisions for Thermal CrackingObjective

JCI-RILEM International Workshop, CONCRACK5, April 24-26, 2017, Japan 11

Provisions for Thermal Cracking

Part Original cement type ModificationColumn capital HPC*1 MPC*2

Cantilever HPC*1 OPC*3

Closure HPC*1 OPC*3+EX*4

Side closure

1st lift HPC*1 OPC*3

2nd lift HPC*1 OPC*3+EX*4

*1: High-early-strength Portland Cement (HPC)*2: Moderate-heat Portland Cement (MPC)*3: Ordinary Portland Cement (OPC)*4: Expansive Additive (EX)

Different types of binders for each part

Cement type and Expansive additive

JCI-RILEM International Workshop, CONCRACK5, April 24-26, 2017, Japan 12

Provisions for Thermal Cracking

Part Method of curing Period

Bridge face(In the spans)

Wet mat and Insulated mat

From casting to the assuranceage of strength

Bridge face(On the piers)

Wet mat and Insulated mat

From casting to the assuranceage of strength(The time when the insulatedmat was installed after thetemperature inside theconcrete reached the peak)

Types of insulated curing

Insulated curing

JCI-RILEM International Workshop, CONCRACK5, April 24-26, 2017, Japan 13

Provisions for Thermal CrackingCooling concrete< Cooling concrete with liquid nitrogen >

Agitator–bodyTruck

Tank lorry withliquid nitrogen

Jet nozzle Scaffolding for jet

JCI-RILEM International Workshop, CONCRACK5, April 24-26, 2017, Japan 14

Provisions for Thermal Cracking

Part Maximum limit concrete temperature at the casting

Management temperature after injection

1st lift 30°C 29°C

2nd lift 26°C 25°C

Management temperature of cooling< Cooling concrete with liquid nitrogen >Cooling concrete

Quantity of LN2 necessary to reduce concrete of1m3 by 1 °C was 14.9 kg/m3°C

JCI-RILEM International Workshop, CONCRACK5, April 24-26, 2017, Japan 15

Fan

Duct

Deflection tube Branched duct

Provisions for Thermal Cracking

< Air-cooling with the use of deflection tube >Cooling concrete

JCI-RILEM International Workshop, CONCRACK5, April 24-26, 2017, Japan 16

Case Conditions of analysis model

1 Standard construction only with OPC

2 Case 1 with MPC

3 Case 2 with insulated curing

4 Case 3 with cooling with LN2 and air-cooling

Provisions for Thermal CrackingEffect of provisions

Cases of 3D-FE analysis in advancefor the column capital part

JCI-RILEM International Workshop, CONCRACK5, April 24-26, 2017, Japan 17

Provisions for Thermal CrackingEffect of provisions< Case 1 > < Case 2 >

Standard constructiononly with OPC

Case 1 with MPC

Target values2nd lift : 1.751st lift : 1.45

JCI-RILEM International Workshop, CONCRACK5, April 24-26, 2017, Japan 18

Provisions for Thermal CrackingEffect of provisions< Case 3 > < Case 4 >

Case 2 with insulated curing Case 3 with LN2-coolingand air-cooling

Target values2nd lift : 1.751st lift : 1.45

JCI-RILEM International Workshop, CONCRACK5, April 24-26, 2017, Japan 19

Provisions for Thermal CrackingEffect of provisions

Result of thermal analysis (Case 4)

YesFirst Construction

Thermal Fitting Analysis

Yes

No

Remaining Constructions to Follow

Confirmation of EachMatter Value for Property

Measurement of Concrete Temperature

No

3D-FE Analysis for Initial Construction

Verification(Satisfy the Limit Values?)

Consideration ofAdditional Provisions

Consideration ofAdditional Provisions

Verification(Satisfy the Limit Values?)

3D-FE Analysis for the RemainingConstructions to Follow

: Measurement point

JCI-RILEM International Workshop, CONCRACK5, April 24-26, 2017, Japan 20

0

10

20

30

40

50

60

70

0 1 2 3 4Tempreature inside concrete(℃

)

(Day)

Prior analysis

Measured value

Fitting analysis0

10

20

30

40

50

60

70

0 1 2 3 4Tempreature inside concrete(℃

)(Day)

Prior analysis

Measured value

Fitting analysis

Provisions for Thermal CrackingEffect of provisions

< Effect of cooling with LN2 > < Effect of air-cooling >

JCI-RILEM International Workshop, CONCRACK5, April 24-26, 2017, Japan 21

Conclusions

It was confirmed that the provisions against the thermalcracking were effective.

It was confirmed that the provision to the cement type withless total heat generation due to the hydration reactionswas effective especially in the 1st lift.And reducing temperature of concrete such as cooling waseffective in the 2nd lift for controlling the thermal crack atthe column capital.The values of thermal properties calculated after the fittinganalysis were almost similar to one of the prior verifications.