Experiments and analyses of fracture properties of grouting mortars

Material experiments for the grouting mortar are performed to evaluate the fracture properties. The fracture mechanical parameters such as the specific fracture energy and the tension softening diagram are analyzed from the load-displacement curves measured using rectangular notched specimens and wedge-splitting procedures. Using these data, the tension-softening diagram of the grouting mortar is proposed and applied to numerical analyses of the wedge-splitting test specimens to investigate the applicability of the model. The analytical results are compared with the experimental results, and the reliability of the tension -softening diagram is examined. It is concluded that the tension-softening diagram proposed is useful for the fracture analysis of the mortar. the slender wedge into a large horizontal component (Fh) and a small vertical component (Fv), which are then applied to the specimen (see Figure 1(b)). The large horizontal component splits the specimen in a manner similar to a bending test. A load cell in the testing machine measures the total force (Fm). Since the wedge angle ( α ) is known, the horizontal component (Fh) is calculated as follows. ) 2 / tan( 2 α m h F F = (1) The displacement of the specimen, referred to as the Crack Mouth Opening Displacement (CMOD), is measured at each end of the groove using a clip gauge. The mean values of the two measurements (d1 and d2) are used to reduce the uncertainty. Tests were performed using a mechanical compression-testing machine with a load capacity of 9.8 kN. The crosshead velocity for each test was 0.67 mm/min. A rectangular notched specimen, illustrated in Figure 2, was used for fracture tests of the mortar. A starter notch (2 mm wide) was cut in the top of the specimen with a stone saw shortly before testing. The ligament length is 60 mm for all specimens. 2.3 Load-displacement diagram The force (Fm) and the two end displacements (d1 and d2) were recorded by an electronic data logger at 1.0-second intervals. The data were then analyzed to produce a load-displacement curve (Fh-CMOD curve). The measured load-displacement curves are given in Figures 3 (a)~(f) for the M1, M2 and M3 mortar at the different ages. The load-displacement graphs represent the curves of the three identical specimens at each material age. The scattering of the measured data in the three specimens at each age was small in these mortar specimens. Large differences between the M1 and M3 mortar were observed in the maximum load as plotted in Figures 3(a) and (e). The results also showed that the maximum load increased slightly with the increasing material age. 3 ANALYSIS OF FRACTURE PARAMETER The load-displacement curves indicated in Figures 3 (a)~(f) characterize the fracture properties of the mortar. In this study, the fracture mechanical parameters, such as the specific fracture energy (Gf) and the tension-softening diagram, are derived from the experimental results. 3.1 Specific fracture energy The area under the load-displacement curve represents the energy needed to fracture the specimen (fracture energy). The specific fracture energy (Gf) is a measure of the crack growth resistance of the material and is defined as the ratio of fracture energy to fracture area, normal to the wedge penetration direction. The specific fracture energy (Gf) of the mortar specimens is determined from the test results and is given in Figure 4. The Gf values of the M1 mortar are 0.035 and 0.038 N/mm at the age of 7 and 28 days respectively and are almost same as those of the M2 and M3 mortar (0.034~0.04 N/mm). The results also (mm) 45 4 5 4 0