Combustion and Mechanical Properties of Wood Impregnated with Aqueous Solutions of Various Ammonium and Phosphate-Based Commercial Fertilizers

This study evaluates the combustion and mechanical behavior of Oriental beech (Fagus orientalis L.) wood impregnated with aqueous solutions of various commercial fertilizers–specifically calcium ammonium nitrate (CAN), triple superphosphate (TSP), and their 1:1 weight-based mixture (CAN+TSP). These fertilizers were selected for their known flame-inhibiting potential due to their ammonium and phosphorus content. Ammonium dihydrogen phosphate (ADF), a widely accepted reference fire retardant, was included for comparison. Specimens were treated with 3 %, 6 %, and 9 % aqueous solutions of fertilizers and ADF and subjected to combustion testing based on ASTM E69, including measurements of mass loss, temperature, CO emissions, time to extinction, and collapse. Mechanical performance was assessed by determining modulus of rupture (MOR) and compression strength parallel to the grain (CSPG) in accordance with TS and ISO standards. The results showed that 9 % solution of ADF yielded the most effective fire-retardant performance, with substantial reductions in mass loss and combustion temperature. In contrast, CAN treatments showed minimal improvement in flammability behavior. Mechanical degradation was evident at higher concentrations across all formulations, though 6 % solution of ADF and 3 % solution of CAN retained mechanical performance closest to untreated wood. These findingssuggest that phosphate-rich fertilizers, especially ADF and TSP, may offer a viable and economical alternative to traditional fire retardants for wood, provided that impregnation concentration is carefully optimized to preserve mechanical integrity.