Issue 50

Q. Hu et alii, Frattura ed Integrità Strutturale, 50 (2019) 638-648; DOI: 10.3221/IGF-ESIS.50.54 645 K-feldspar at 2θ = 27.4 ° decreased while the diffraction peak intensity of plagioclase at 2θ = 28.0 ° increased with increasing temperature. To further interpret the variation, the full width at half maximum (FWHM) of K-feldspar at 2θ = 27.4 ° and plagioclase at 2θ = 28.0 ° in two groups as temperature increased were calculated, as shown in Fig. 8. The FWHM variation of group A is consistent with the corresponding UCS data. However, the group B exhibits nothing similar to the phenomenon. It indicated that the microwave irradiation affected the mechanical performance of rock by leading a similar and irreversible variation on crystal structures of K-feldspar and plagioclase, and this affair significantly contributed to the mechanical performance variation of granite irradiated by microwaves. In particular, the plagioclase expresses a more intense response to microwave irradiation than K-feldspar. To meet the practical application, analysing the plagioclase crystallinities at different temperatures possibly can be used as guide to preliminarily estimate the structural deterioration of granite irradiated by microwaves before carrying out the time-consuming mechanical performance tests. Figure 7 : XRD patterns of granite powders before and after heating treatments: (a) microwave irradiation group and (b) resistance- heating group.