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 Taiheiyo Cement Corporation, Japan Ryoichi SATO Hiroshima University, Japan Hiroshima University, Japan 1

Influence of dosage of Expansive additive and/or shrinkage reducer 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) 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 2

 W/(C+EX)= 0.3, W= 175 kg/m 3  Slump flow value; mm  Targeted concrete strength; 70 N/mm 2 Combinations of key-materials Cem. EX (kg/m 3 ) Ordi- nary SRA (kg/m 3 ) 06912N-0-0N-0-6N-0-9N-0-12N-30-0N-30-6N-30-9N-30-12N-40-0N-40-6N-40-9N-40-12N-50-0N-50-6N-50-9N-50-12N-60-0N-60-6N-60-9N Belite- rich Low heat 06912L-0-0L-0-6L-0-9L-0-12L-30-0L-30-6L-30-9L-30-12L-40-0L-40-6L-40-9L-40-12L-50-0L-50-6L-50-9L-50-12L-60-0L-60-6L-60-9L Mixture proportioning  EX; Lime-based expansive additive  SRA; Lower-alcohol alkyleneoxide adduct-based shrinkage reducer 3

 Before demolding Testing Method for Autogenous Shrinkage/Expansion of Concrete Testing Method for Autogenous Shrinkage/Expansion of Concrete  After demolding JIS A 1129 (contact-type strain gage) JIS A 1129 (contact-type strain gage) Autogenous shrinkage/expansion strain= (Measured strain) – (thermal strain) (Measured strain) – (thermal strain) Measurement of autogenous length change JCI method (originally proposed by Tazawa & Miyazawa) 4 20 o C coefficient of thermal expansion of concrete; assumed to be 10 x / o C

: 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 5 Definition of strain in this study

 AS of LPC-HSC is obviously small compared with OPC-HSC.  Prediction by JSCE Code is in good agreement with measurement. Effectiveness of Berite-rich low heat Portland cement 6 JSCE 0.4 LPC JSCE Code-2002 OPC +40% ‐ 40% +40% (by Miyazawa et al.) Initial set

 SRA is obviously effective in reducing AS.  AS of LPC-based HSC is almost cancelled by adding SRA. Ras=0.0008SRA SRA+1 Ras=0.0024SRA SRA+1 始発 7 Effectiveness of shrinkage reducing agent(SRA) LPC OPC Age: 91days LPC OPC Initial set

(Expansion) (Shrinkage) (Expansion) (Shrinkage) Effectiveness of expansive additive (EX) 8  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 LPCOPC 50% 80%

 Compensation of AS is more significant for LPC-based HSC. Reason; difference in early-age mechanical property, etc. Reason; difference in early-age mechanical property, etc. Description of the effect of expansive additive (EX) ε ex∞ =0.144EX EX ε ex∞ =0.061EX EX compensation of AS from final set of EX-added HSC Definition of compensation of AS 9 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 No SRA ε ex+sra∞ =0.142EX EX ε ex+sra∞ =0.278EX EX No SRA SRA=6 ～ 12 kg/m 3 10  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. Reason; delicate change of hydration reaction of EX and cement by adding SRA, etc. --- further investigations is needed for detailed explanation, --- further investigations is needed for detailed explanation, from both chemical and mechanical point of view. from both chemical and mechanical point of view. LPCOPC Age: 91days Synergistic effect SRA=6 ～ 12 kg/m 3

11 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

Basic equation; JSCE Code equation for AS End value Development property a=0.6, b=0.5 for W/C=0.3 Initial set 12 Prediction model for autogenous shrinkage/expansion strain, considered effect of EX and/or SRA

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 13 LPC OPC

Average of “c” & “d” obtained from least square method for EX-added HSC; 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 14 LPC OPC End value of compensation of AS OPC; c=0.8, d=0.5 LPC; c=0.5, d=0.6

LPC 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= Development property of compensation of AS Age (days) LPC OPC Average; c=0.8, d=0.5

+20% -20% SRA-added HSC Prediction accuracy; 20 % 16 Accuracy of prediction model +20% -20% +20% -20% EX-added HSC EX+SRA-added HSC

It is surely confirmed that HSCs with various low shrinkage/expansion strain properties can be produced by sole/combined use of investigated materials. It is surely confirmed that HSCs with various low shrinkage/expansion strain properties can be produced by sole/combined use of investigated materials. It is demonstrated that the investigated equations have accuracy of 20 % for predicting autogenous shrinkage /expansion strain of low-shrinkage/expansion HSCs. 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 17 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 !!

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 -High cracking resistance -Durable RC structure 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 admixturesLow-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

Autogenous shrinkage of cement paste with W/C of 0.3 (x10 -6 ) = 2.15 ＊ (C 3 S%) – 5.49 ＊ (C 2 S%) ＊ (C 3 A%) ＊ (C 4 AF%) where, where, (C 3 S%): Content of C 3 S (mass%) ………………… [by Miyazawa, Tazawa, 1996] ………………… [by Miyazawa, Tazawa, 1996] LPC has lower autogenous shrinkage and resultant-induced stress 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 400x x10 -6 High C 2 S, Low C 3 A Calculated value

Basic equation; JSCE Code equation for AS End value Development property a=0.6, b=0.5 for W/C=0.3 Initial set 22 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 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 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 EX+SRA effect –Superposition of compensation of AS for EX+SRA-added HSC, including synergistic effect, and AS of SRA-added HSC