Ageing of annealed and chemically strengthened glass
Eight 45-year-old naturally aged windows collected from two buildings in two different locations revealed surface characteristic bending strengths in the range of 38-54 MPa. An artificial ageing method by sandfall was developed to reproduce the weakest failure stresses among the naturally aged samples. When this method was applied to chemically strengthened glass, the results varied depending on the glass composition and the strengthening cycle. To achieve the characteristic bending strength of 150 MPa specified by EN 12337, after the artificial ageing, soda-lime silicate glass needed routine strengthening cycle of 24 hours, whereas the newly developed Falcon® glass performed well after a shorter 8-hour strengthening cycle, with characteristic bending strength still above 300 MPa after artificial ageing. This study also includes a comparison with other studies in the literature regarding natural ageing and the application of sandfall artificial ageing to annealed glass and chemically strengthened glass.