Control of Cracking in Early Age Concrete

Hirozo Mihashi, Tohoku University, Japan. Folker H. Wittmann, ETH-Zürich, Switzerland.

• Preface Material properties and hydration models: Material properties influencing early cracking of concrete; Determination of initial degree of hydration by means of ultrasonic measurements; Thermal expansion coefficient of concrete at very early ages; Influence of curing temperature on mechanical properties and evaluation of the equivalent age; Modelling hydration and risk of early age thermal cracking of concrete; Unified solidification model of hardening concrete composite; Mathematical models for degree of hydration, moisture and temperature distributions in early age concrete : Mathematical model for hydration of cement and formation of the cement microstructure. Thermal stress measurement and analysis: Strain localization in transient concrete state and potential crack location; Numerical simulation of temperature and stress development in high-strength concrete Columns. Strain localization in transient concrete state and potential crack location; Numerical simulation of temperature and stress development in high-strength concrete Columns; Development of a new device for measuring thermal stresses; Measurement and analysis of thermal stresses in massive concrete block foundation; Realistic analysis of thermal and shrinkage stresses in concrete structures at early ages; Influence of environmental parameters on thermal stresses; Evaluation of mass concrete practice by using Compensation-Plane-Point Method; Experimental estimation of thermal cracking using the modified temperature-stress testing machine. Shrinkage and creep: Autogenous shrinkage: present understanding and future research needs; Restraint stress due to autogenous shrinkage and drying shrinkage in high-strength Concrete; Evaluation of autogenous shrinkage of concrete based on mechanical properties of the cement paste matrix; Deformation and stress in high-strength concrete due to autogenous shrinkage and thermal expansion; Autogenous shrinkage of cementitious materials at early ages; Early age shrinkage properties of highly strengthened aerated lightweight concrete including waste glass aggregates; Drying shrinkage cracking of concrete kept under dry air conditions from early age; Numerical simulation model for drying shrinkage and cracking of early age concrete; Influence of elevated temperature on creep and relaxation of early age concrete; Effective elastic modulus for thermal stress analysis considering early age creep behavior; Evaluation of creep of high-strength concrete at early ages; Mechanical properties and creep behavior of high-strength concrete in early age; Experimental research about early age creep of B65 and B85 concrete mixtures; Restrained deformation of high-strength concrete using low-heat Portland cement; Crack criteria for early age concrete: Experimental research on the test methods for surface cracking of concrete; Effects of stress-strain relationship and relaxation on restraint stress and crack formation in young concrete members; Predicting cracks in hardening concrete using a stress-based cracking criterion; Tensile behavior of early age concrete measured by uniaxial tension test; Controlling technologies and practical applications: Shrinkage reduced in high-performance concrete by internal curing using pre-soaked lightweight aggregate; Crack resistant mechanism of expansive concrete in early ages; Preliminary notions for predicting cracking of expansive concrete based on its Mechanism; Experimental study on shrinkage compensating high-fluidity concrete; Control of thermal cracking by pipe cooling system in concrete structures; Experimental study on heat transfer coefficient in convection flow of young concrete at pipe cooling; Crack control for the massive concrete structures of the new central railway station in Berlin, Germany; Development of a smart material to mitigate thermal stress in early age concrete.