Issue 49

L. Restuccia, Frattura ed Integrità Strutturale, 49 (2019) 676-689; DOI: 10.3221/IGF-ESIS.49.61 682 To evaluate the fracture properties for the different mixes, standard three-point bending (TPB) tests have been performed according to RILEM Recommendations [27,28]. The specimens had dimension of 160x40x40 mm, with a span/depth ratio equal to 4 and a notch/depth ratio equal to 1/3. A single column displacement-controlled testing machine Zwick Line-Z050, with load cell of 50 kN was used with a crosshead speed of 0.01 mm/min. Crack Mouth Opening Displacement (CMOD) has been controlled by using a clip-on- gauge, placed across the notch and held in position by two steel knife-edges glued to the specimen (Fig. 4). After flexural testing, each halves of the broken prism have been subjected to compression test by using an MTS servo- hydraulic machine (a modified Zwick machine), by loading its side faces through auxiliary plates of tungsten carbide of thickness 10 mm and surface (40 x 40 mm). The tests have been performed with 0.05 mm/s test speed (Fig. 5). Figure 5 : Set up and test of experimental mortars: compression test . RESULTS AND DISCUSSION Results by XRD and FESEM analysis RD patterns of RSw showed the presence in all the samples of calcite (JCPDS card #05-0586) and quartz (JCPDS card #46-1045) as major constituents. Paragonite (a sodium aluminum silicate hydroxide, JCPDS card #24-1047), phlogopite (a potassium magnesium aluminum silicate hydroxide, JCPDS card #10-0493) and clinochlore (a magnesium aluminum iron silicate hydroxide, JCPDS card #07-0078) were secondary phases. Gismondine (a calcium aluminum silicate hydrate, JCPDS card n°39-1373), probably due to hydrated cement residues, was found as traces (Fig. 6). Paragonite and clinochlore came from the aggregate fraction of former concrete, while calcite could have different origins: from aggregates, as cement filler, and from concrete degradation process (carbonation). Field Emission Scanning Electron Microscopy analysis (FESEM) were carried out for observing the shape of different fraction and for evaluating the capability of these recycled washed grains to ensure a good adherence to the cement paste. Generally, it seems that the smaller fraction has a sharpener shape (0.08 and 0.16 mm), which could ensure a better adhesion with the cement matrix (Fig. 7). The larger grains (≥ 1.00 mm) instead have a more rounded form (Fig. 8). X