High-temperature triaxial torsional creep tests of concrete at various hygral conditions

Abstract

Results of an initial series of six-day creep tests under a program aimed at establishing fundamental deformation properties of concrete at high temperatures under triaxial loading with shear and various hygral conditions, both constant and transient, are reported. The tests are conducted in a novel large triaxial torsional testing machine with hygrothermal control. Tested are cylinders of six inch diameter, sealed or unsealed, loaded by compressive axial force, chamber pressure and torque. Some specimens are sealed wet, some are sealed after drying in an oven, and some are let to dry during the test. Significant differences in creep at various hygro-thermal conditions are observed. Particularly interesting is the fact that hygro-thermal changes affect not only normal creep strains but also shear creep strains. The results are of interest for the formulation of constitutive relations needed for the analysis of nuclear reactor accidents, radioactive waste disposal, and fire resistance.