Study On Volume Changes Of High Performance Concrete Under Multi-Variable Coupling Participation

Complicated volume changes of high performance concrete (HPC)is one of significant causes which results in its early-age cracking. Thisdissertation experimentally investigated early-age volume changes of HPCincluding autogenous shrinkage, thermal deformation and drying shrinkageunder multi-parameters including water-cement ratio (W/C), curingtemperature and drying initiation age. And furthermore, a compositeadmixture for reducing shrinkage (CARS) was used for improving volumechanges of HPC and its effectiveness is evaluated experimentally.The conclusions based on the present research work can be drawnas follows: (1) Lower W/C and higher curing temperature result in fasterdevelopment rate and higher value of autogenous shrinkage strain. LowerW/C also lead to the faster hydration reaction and earlier and higher peaktemperature. (2) The characteristic of autogenous shrinkage under differentcuring temperatures cannot be well described with maturity concepts. (3)Drying shrinkage is well related to autogenous shrinkage after drying andweight loss of testing specimens. (4) Higher curing temperature and lower W/C bring on faster development of total shrinkage strain at early ages.When it comes to total shrinkage strain at the age of 28 days, no obviousdifferences exist between concrete mixers with different W/C and uniformcuring temperature. (5) The lower W/C is, the higher ratio of autogenousshrinkage strain in total shrinkage strain under drying conditions. (6) Theaddition of CARS significantly reduced autogenous shrinkage and dryingshrinkage strain. Compressive strength and elastic modulus are reduced dueto the addition of CARS.