Improvement of granite and concrete cutting efficiency using mixed-abrasives

Garnet and steel shot have advantages and disadvantages in terms of cutting performance and economic efficiency as single abrasive materials for cutting rock and concrete using abrasive waterjet. However, the application of abrasive waterjet technology in construction sites is still limited due to the cutting performance and cost limitations of single abrasive. A new strategy is needed for effective field application of abrasive waterjet technology. In this study, mixed-abrasives, which are mixtures of garnet and steel shot at various mass ratios, were applied to abrasive waterjet cutting to address the limitations of garnet and steel shot, and optimize their advantages. The cutting characteristics of mixed-abrasives were experimentally evaluated, and cost analysis of granite and concrete was performed. Granite and concrete used in the cutting experiment are brittle materials with P-wave velocity of 5346 m/s and 3968 m/s, a uniaxial compressive strength of 236 MPa and 49 MPa, respectively. Mixed-abrasives were classified into fresh and recycled mixed-abrasives. The latter was categorized into reused and submerged conditions, and its cutting performance was evaluated using natural and oven-drying methods. To maximize cutting efficiency in terms of specific energy, it is desirable to apply an abrasive flow rate of approximately 11 g/s. By comprehensively considering cutting performance and economic efficiency, the optimal mixing ratio of garnet and steel shot was 50:50. The critical abrasive collect rates of granite and concrete were evaluated at 18–21 % and 28–37 %, respectively, depending on the abrasive cost ratio. In conclusion, it was confirmed that efficient cutting using mixed-abrasives is possible in terms of practical applications. In addition, the results of this study provide appropriate guidelines for method design considering market price fluctuations of abrasives. Therefore, it is expected that effective application of abrasive waterjet technology to the field is possible.