Takafumi Noguchi The University of Tokyo, Japan Park Sun-Gyu Yonsei University, Korea

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Mechanical Properties of HPC with Expansive Additive and Shrinkage Reducing Admixture under Simulated Completely-Restrained Condition at Early Age. Takafumi Noguchi The University of Tokyo, Japan Park Sun-Gyu Yonsei University, Korea Ippei Maruyama Hiroshima University, Japan. Background. - PowerPoint PPT Presentation

Text of Takafumi Noguchi The University of Tokyo, Japan Park Sun-Gyu Yonsei University, Korea

  • Mechanical Properties of HPC withExpansive Additive andShrinkage Reducing Admixture under Simulated Completely-Restrained Condition at Early AgeTakafumi NoguchiThe University of Tokyo, JapanPark Sun-GyuYonsei University, KoreaIppei MaruyamaHiroshima University, Japan

  • BackgroundHigh-performance Concrete (Low W/C)Self-desiccationAutogenous ShrinkageUnder Restraint ConditionCrackingInfluence on Durability & AestheticUse ofExpansive AdditionShrinkage Reducing Admixture

  • Objective of StudyBehaviour of Early Age HPC with and withoutExpansive AdditionShrinkage Reducing AdmixtureRestraint Free ConditionShrinkage StrainUnder Restraint ConditionStrain & StressCreep BehaviourControl of Autogenous Shrinkage Cracking

  • Variable Restraint Testing Machine Fresh concrete is cast into the framework of the testing machine.Specimen size is 1500 mm in length and 100 mm x 100 mm in cross sectional areaThe ends of specimen are fixed to the cross-head, which is fixed to the frame, by claws which hold the concrete specimen and are able to exert tensile or compressive force. The load through the specimen is monitored by a load cell with accuracy of 1 N.The longitudinal deformation of concrete specimen is monitored by four LVDTs with accuracy of 0.125 m.Experiment is commenced after the concrete setting.

  • Program Flow of Simulated Completely-Restrained TestCompletely restrained condition is simulated by maintaining the total deformation of the specimen within a threshold, which is defined as the permissible change in the length of the specimen.There are two controlling triggers.One is stress trigger.Another is strain trigger.While repeating this process in VRTM,a completely-restrained condition is achieved andthe stress generated by shrinkage is measured.

  • Mix Proportions of Concrete

  • Experiments Compressive Strength Tensile StrengthModulus of ElasticityFree Autogenous ShrinkageSealed with a polyester film at 20 CStress Development under Simulated Completely-RestraintSealed with a polyester film at 20 CTrigger of stress and strain : 0.01 MPa and 2 x 10-6

  • Mechanical Properties of Concrete

  • Autogenous ShrinkageAutogenous shrinkages of NHC and SHC occurres at a rapid rate in the first few hours and the rate decreased afterward.In EHC, after a few hours expansion is observed.Expansive addition and shrinkage reducing admixture can obviously reduce the autogenous shrinkage of HPC.

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