Uni-Axial Tensile Test Setup
The uni-axial tensile tests were also done in a Zwick Z250 universal testing machine. Hooks were cast at the two ends of the 100 x 100 x 500 mm3 specimens to facilitate the gripping of the specimens in the hydraulic grips of the testing machine. A notch with depth of 10 mm was sawn on all four sides of the sample at the centre to ensure the position of the crack. The crack widening was measured using two 10 mm HBM LVDTs connected to two aluminium frames in turn connected to the specimen using a 100 mm gauge length. The test setup is shown in Fig. 3. Note this results in boundary conditions very close to pinned at the top and bottom.
Uni-Axial Tensile Creep Test Setup
The uni-axial tensile creep tests were done using the same specimens as presented in Sect. 2.3. The load was however applied using two lever arms connected to two samples in series in a loading frame, shown in Fig. 4. A total of eight loading frames were available (i.e. 16 samples could be tested at one point of time) and the ratio of applied weights to applied load in the samples was calibrated using a load cell. This calibration was done prior to the tests with the load cell in the position of the samples and the load cell was then removed before each test. The crack mouth opening was monitored using two 10 mm HBM LVDTs connected to an aluminium frame using a gauge length of 70 mm over the notch, shown in Fig. 4. The readings were taken at regular intervals, ranging from one per second in the
Fig. 3 The uni-axial tensile test setup beginning to a few a day after a few months. The safety stopper shown in Fig. 4 was also used to apply the load, i.e. the level arms were loaded with the safety stopper in place and the stopper was then removed within a few seconds to apply the load.
Drying Shrinkage Test Setup
The drying shrinkage was also measured in order to subtract the shrinkage component from the displacement measured over the gauge length in the tensile creep test setup. The setup and results are not discussed in this paper and the reader is referred to  for the details. Note that the shrinkage deformations were subtracted from the results shown in this paper.
Fig. 4 Uni-axial tensile creep test setup showing the lever arms, the safety stopper and the aluminium frames