The main costs for modern rotary kiln incinerators are refractory brick maintenance. Every 1-3 years, parts or the entire brick lining has to be renewed due to refractory wear and tear. Often, the blame is laid on thermo-chemical corrosion. To reassess this prevailing dogma, a comprehensive wear mechanism was elaborated that includes the impact of bottom ash characteristics at operating temperatures. Thermodynamic calculations were employed as well as a post-mortem analysis of refractory bricks from three rotary kilns. Changes in chemical and mineralogical composition and microstructure were examined. Surprisingly, results show that there is no significant thermo-chemical reaction between refractory material and the molten bottom ash. In fact, the melt penetrates open pores by capillary action up to 5 mm in depth. Under this infiltrated zone, serious cracks are systematically visible in all type of bricks. We suspect a mismatch of thermal expansion coefficients to be the cause of crack initiation. These cracks lead finally to spalling of degraded refractory layers. Therefore, refractory materials used nowadays are not optimal. To conclude, experimental based guidelines are provided that may help operators extend the lifetime of the refractory bricks and reduce maintenance cost significantly.