The temperature control system of the TSTM is similar to that of the Dilation Rig.
The stress development measured in the TSTM is the net effect of all the parameters acting to produce restraint stresses in hardening concrete (ise., thermal dilation, autogenous shrinkage, elastic modulus, and creep/relaxation properties).
In the current study, the tests were performed parallel in the Dilation Rig and TSTM. Thermal dilation and autogenous shrinkage occur simultaneously in the concrete specimens in TSTM and Dilation Rig.
The integral type of formulation is used in the 1D analysis of restraint stress development in the TSTM:
The constitutive behavior of young concrete in stress rig (TSTM) is defined by the equation as proposed by the CEBFIP ; the strain rate [DELTA][[epsilon].sub.j] at time [t.sub.j] may be composed of thermal strain, autogenous strain, creep strain, elastic strain and transient thermal creep strain.
where [epsilon] is the measured strain in TSTM, [[epsilon].sub.th] is the thermal dilation, [[epsilon].sub.sh] is the autogenous shrinkage, [[epsilon].sub.el] is the elastic strain, [[epsilon].sub.cr] is the creep strain, and [[epsilon].sub.ttc] is the transient thermal creep strain.
Bjontegaard, "Calibration of material models against TSTM
test for crack risk assessment of early age concrete containing fly ash," Advances in Materials Science and Engineering, vol.
TSTM (Figure 1) is a closed-looped uniaxial restrained testing device which has four main functions: the measurement of load, the measurement and control of temperature, the measurement and control of deformation, and the measurement of reinforcement stain.
Besides, "temperature control system of TSTM" is adopted to control the specimen temperature, which is composed of temperature controlled mould (test mould), pump, circulating pipes, and temperature control box (Figure 3(b)).
To investigate the effect of reinforcement on cracking, the strain values of reinforcement bars are measured by the improved TSTM. Strain gauges are adopted to measure the deformation of reinforcement (Figure 4(a)).
Firstly, fresh concrete was cast in the test mould of TSTM, and a layer of plastic sheet was covered on the surface of concrete to maintain constant humidity.
The same as plain concrete tests, the TSTM test of RC also has three stages: temperature rise stage, constant temperature stage, and cooling stage.