# Presentation: 140159

## An Investigation of Prediction Model for Autogenous Shrinkage/Expansion Strain of Low-shrinkage HSC

***Fourth International Seminar on Self-desiccation and Its Importance in Concrete Technology ***
***20/June/05, Gaithersburg, Maryland, USA***

***Makoto TANIMURA, Yuji MITANI***
***  ******Taiheiyo Cement Corporation, Japan***
***Ryoichi SATO***
***  ******Hiroshima University, Japan***

## Influence of dosage of Expansive additive and/or shrinkage reducer

***Prediction model for autogenous shrinkage/expansion strain of low-shrinkage/expansion HSCs (required in practice)***

*** ******Importance of autogenous shrinkage in HSC***
*** ******Necessity of reducing autogenous shrinkage***
***----- well known!! (JCI committee 1996 & 2002)***
***Effectiveness of expansive additive, shrinkage reducer, High C******2******S and low C******3******A-cement***
*** ******Effectiveness for reduction of restrained-shrinkage stress, improvement of structural performance of RC members***

_***Objectives***_

**(Tazawa & Miyazawa, at least in 1994)**

**(by authors, presented by SUZUKI)**

_***Background***_

##  W/(C+EX)= 0.3, W= 175 kg/m3

*** ******Slump flow value; 500-700 mm***
*** ******Targeted concrete strength; 70 N/mm******2***

_***Combinations of key-materials***_

| Cem. | EX (kg/m3) |  | 0 | 30 | 40 | 50 | 60 |
| --- | --- | --- | --- | --- | --- | --- | --- |
| Ordi-nary | SRA
(kg/m3) | 0
6
9
12 | N-0-0
N-0-6
N-0-9
N-0-12 | N-30-0
N-30-6
N-30-9
N-30-12 | N-40-0
N-40-6
N-40-9
N-40-12 | N-50-0
N-50-6
N-50-9
N-50-12 | N-60-0
N-60-6
N-60-9
N-60-12 |
| Belite-rich
Low heat |  | 0
6
9
12 | L-0-0
L-0-6
L-0-9
L-0-12 | L-30-0
L-30-6
L-30-9
L-30-12 | L-40-0
L-40-6
L-40-9
L-40-12 | L-50-0
L-50-6
L-50-9
L-50-12 | L-60-0
L-60-6
L-60-9
L-60-12 |

_***Mixture proportioning***_

*** ******EX; Lime-based expansive additive***
*** ******SRA; Lower-alcohol alkyleneoxide adduct-based shrinkage reducer***

## Measurement of autogenous length change

** ****Before demolding**
**   ****Testing Method for Autogenous Shrinkage/Expansion of Concrete **
** ****After demolding**
**   ****JIS A 1129 (contact-type strain gage)   **

**Autogenous shrinkage/expansion strain=**
**                                           ****(Measured strain) – (thermal strain)**

_***Measurement of autogenous length change***_

**JCI method**

**(originally proposed by Tazawa & Miyazawa)**

**20****o****C**

- coefficient of thermal expansion of concrete; assumed to be 10 x 10-6/oC

## Definition of strain in this study

- : autogenous shrinkage strain from initial setting time
- : drying shrinkage strain
- : total shrinkage strain from initial setting time (                                        )
- : total shrinkage strain from start of drying
- : autogenous shrinkage strain from start of drying

- According to JSCE Design Code 2002

- Investigation on autogenous shrinkage

_***Definition of strain in this study***_

## Effectiveness of Berite-rich low heat Portland cement

*** ******Prediction by JSCE Code is in good agreement with measurement. ***

_***Effectiveness of Berite-rich low heat Portland cement***_

**JSCE****  **_**0.4**_

**LPC**

**JSCE Code-2002**

**OPC**

**+40%**

**‐****40%**

**‐****40%**

**+40%**

**(by Miyazawa et al.)**

**Initial set**

## Effectiveness of shrinkage reducing agent(SRA)

*** ******SRA is obviously effective in reducing AS.***
*** ******AS of LPC-based HSC is almost cancelled by adding SRA.***

- Ras=0.0008SRA2-0.035SRA+1

- Ras=0.0024SRA2-0.094SRA+1

**始発**

_***Effectiveness of shrinkage reducing agent(SRA)***_

**LPC**

**OPC**

**Age: 91days**

**LPC**

**OPC**

**Initial set**

## Effectiveness of expansive additive (EX)

_***Effectiveness of expansive additive (EX)***_

*** ******EX effectively compensate AS.***
*** ******Absolute expansion strain is dependent upon AS behavior of reference HSC.***
*** ******Combination of LPC & EX; achievement of expansive HSCs***

**Initial set**

**LPC**

**OPC**

**50%**

**80%**

## Description of the effect of expansive additive (EX)

*** ******Compensation of AS is more significant for LPC-based HSC.***
***   ******Reason; difference in early-age mechanical property, etc.***

_***Description of the effect of expansive additive (EX)***_

- εex∞=0.144EX2+4.47EX

- εex∞=0.061EX2+5.82EX

**compensation of AS from final set **
**of EX-added HSC**

- Definition of compensation of AS

**LPC**

**OPC**

**Age: 91days**

- Age

- Expansion

- Shrinkage

- (Initial setting)

- (Final setting)

**AS from initial set of EX-added HSC**

## Effectiveness of combined use of EX and SRA

_***Effectiveness of combined use of EX and SRA***_

**No SRA**

- εex+sra∞=0.142EX2
-                             +3.08EX

- εex+sra∞=0.278EX2
-                              +0.039EX

**No SRA**

**SRA=6****~****12 kg/m****3**

*** ******Significant synergistic effect is observed when EX content of more than 40 kg/m******3***
***   ******Reason; delicate change of hydration reaction of EX and cement by adding SRA, etc.***
***   ******--- further investigations is needed for detailed explanation,***
***   ******from both chemical and mechanical point of view.***

**LPC**

**OPC**

**Age: 91days**

**Age: 91days**

**Synergistic effect**

**Synergistic effect**

**SRA=6****~****12 kg/m****3**

## Definition of compensation of AS for EX+SRA-added HSC

_***Definition of compensation of AS for EX+SRA-added HSC***_

- Expansion

- Age

- Shrinkage

- (Initial setting)

- (Final setting)

**AS from initial set of SRA-added HSC**

**compensation of AS from final set of EX+SRA-added HSC**

**AS from initial set of EX+SRA-added HSC**

## Prediction model for autogenous shrinkage/expansion strain, considered effect of EX and/or SRA 

**End value**

**Development property**
**a=0.6, b=0.5 for W/C=0.3 **

**Initial set**

_***Prediction model for autogenous shrinkage/expansion strain, considered effect of EX and/or SRA ***_

## Prediction model considering SRA effect

_***Prediction model considering SRA effect***_

**JSCE Code**

- Average of “a” & “b” obtained from least square method for SRA-added HSC;
**a=0.62****,****b=0.48**

- Same as that of JSCE Code

**Reduction of end value**

**LPC**

**OPC**

## Prediction model considering EX effect

-    **c=0.8****,****d=0.5 for OPC**
**   ****c=0.5, d=0.6 for LPC**

_***Prediction model considering EX effect***_

- According to values below

**Development property of compensation of AS**

**LPC**

**OPC**

**End value of compensation of AS**

**OPC; c=0.8, d=0.5**

**LPC; c=0.5, d=0.6**

## Prediction model considering EX+SRA effect

**OPC**

- Same as that of EX-HSC

**End value of compensation of AS for EX+SRA-HSC**

_***Prediction model considering EX+SRA effect***_

**Average;**
**c=0.5, d=0.6**

**Development property of compensation of AS**

**Age (days)**

**Age (days)**

**LPC**

**OPC**

**Average;**
**c=0.8, d=0.5**

## Accuracy of prediction model

**SRA-added HSC**

**Prediction accuracy;  20 %**

_***Accuracy of prediction model***_

**EX-added HSC**

**EX+SRA-added HSC**

## Conclusions

*** ******It is demonstrated that the investigated equations have accuracy of  20 % for predicting autogenous shrinkage /expansion strain of low-shrinkage/expansion HSCs.***
***(Further investigation is needed for temperature effect) ***

_***Conclusions***_

***On the other hand, addition of EX and/or SRA influence the strength of HSC. Therefore, suitable dosage of EX and/or SRA as well as W/C should be determined by considering both low-shrinkage performance and high-strength performance.***

## Thank you !!

***Thank you !!***

## Necessity of low-shrinkage HSC

***High-mechanical performance and high-durability***

_***Necessity of low-shrinkage HSC***_

***Significant autogenous***
***  ******shrinkage***
***Tensile restrained-stress   ***
***  ******before loading***
***Deterioration of serviceability performance of RC members***

**Low-shrinkage HSC****-High cracking resistance****-Durable RC structure**

***High-strength***

***Low shrinkage***

***High-flowability***

***Assignment***

***Additional performance***

***generalization***

## Approach for low-shrinkage HSC

***Belite-rich Portland cement***

***Low-heat Portland cement***

***Special admixtures***

***Low-shrinkage cement***

***Expansive additive***

***Shrinkage reducing agent***

***Autogenous strain***

***LPC***

***Conventional HSC***

***EX+SRA***

***EX***

***SRA***

***Combination***

***Expansion rather than shrinkage***

***Autogenous strain***

***Age***

***Control of autogenous shrinkage***

## Influence of mineral compositions of cement on autogenous shrinkage 

***=  2.15*************(C******3******S%) – 5.49*************(C******2******S%) + 68.7*************(C******3******A%) + 48.5*************(C******4******AF%)***
*** ******where,***
***(C******3******S%): Content of C******3******S (mass%)***
***          .....................                         ******[by Miyazawa, Tazawa, 1996]***

*** ******LPC has lower autogenous shrinkage and resultant-induced stress***

_***Influence of mineral compositions of cement ***__***on autogenous shrinkage ***_

_***Mineral compositions of Portland cement in Japan***_

***400x10******-6***

***1000x10******-6***

***High C******2******S, Low C******3******A***

**Calculated value**

## Prediction model for autogenous shrinkage/expansion strain, considered effect of EX and/or SRA 

**End value**

**Development property**
**a=0.6, b=0.5 for W/C=0.3 **

**Initial set**

_***Prediction model for autogenous shrinkage/expansion strain, considered effect of EX and/or SRA ***_

***Approach for investigating prediction equation;***
*** ******SRA effect -- Reduction of end value of AS***
*** ******EX effect – Superposition of compensation of AS and AS of   reference HSC based on JSCE-code equation***
*** ******EX+SRA effect –Superposition of compensation of AS for EX+SRA-added HSC, including synergistic effect , and AS of SRA-added HSC***