Razi University

  Magnesium oxide panels have been considered as one of the mineral materials used in dry construction, partition walls, interior coatings and fire protection systems. However, the thermal performance, moisture resistance and mechanical stability of these panels depend on characteristics such as thickness, type of coating, thermal conditions and humidity level. The present study aimed to investigate the effect of thickness and type of coating on fireproof performance, moisture resistance and mechanical properties of magnesium oxide panels. This study is applied in terms of its purpose and experimental-descriptive in terms of its implementation method. MgO panel samples with different thicknesses, depending on the type of test, were investigated in the range of 8 to 16 mm. The tests included evaluation of thermal and non-combustible behavior, density, water permeability, environmental durability cycles, compressive strength, flexural strength and soft and hard impact tests.   The compressive strength of the samples was investigated at ambient temperature and after exposure to temperatures of 600 and 1200 °C. Also, the flexural strength was evaluated under ambient conditions, high temperatures and relative humidities of 50 and 100%. In addition, the effect of cold traffic coating on moisture behavior and the effect of expanding fireproof coating on thermal stability of the panels were studied. The results showed that increasing the thickness was accompanied by an increase in compressive strength, flexural strength and capacity recorded in impact tests. The 16 mm sample showed the highest initial strength and the highest residual strength after thermal exposure in most tests. The temperature of 600 °C caused a limited decrease in compressive and flexural strength; while at 1200 °C, the decrease in strengths became more severe.   The loss of compressive strength at 1200°C was about 55%, and the loss of flexural strength ranged from 38.44 to 60%, depending on the thickness of the sample. Humidity also caused a limited decrease in flexural strength; the intensity of the effect of saturated humidity was greater than that of average humidity, but much less than that of very high heat. The results of the intumescent coating test showed that this coating, when directly exposed to 1200°C, created an effective thermal protective layer on the panel surface. The coated samples did not experience significant extensive cracking, delamination, or delamination, and the thermal effects did not extend to the middle layers and core of the panel. Also, the mechanical strengths of the coated samples did not show a significant decrease after heating. Overall, increasing the thickness improved the mechanical capacity and thermal stability of the MgO panels, and the intumescent coating was also effective in reducing heat penetration and maintaining the structural integrity of the panel.   However, generalizing the results to all MgO products and determining the fire resistance class requires additional tests and evaluation of the entire system, including panels, cladding, substructure and connections.