New approach for delaying the internal temperature rise of fire resistant mortar made with coated aggregate

Scientifically, resistant properties of steel structures decrease rapidly with an increase of the temperature. Therefore, steel structure is protected with low thermal conductivity materials from high temperatures. Thus, in this study, for developing fire resistance mortars on the surface of steel structure, the coated aggregate was developed with the zeolite aggregate, paraffin, and aluminium hydroxide. In case of paraffin and aluminium hydroxide, they were used as the coating materials on the surface of zeolite aggregates. First, aluminium hydroxide was coated on the surface of the zeolite aggregate with polymer as the bonding material. After that, paraffin was coated on the surface of coated aggregate with aluminium hydroxide. After the coated aggregate were developed, physical and chemical experiments were conducted. The results of the mechanical experiments presented that compressive strength of specimens with coated aggregates was decreased in comparison with the general specimen. In addition, the bonding strength test indicated that every specimen with or without coated aggregates showed similar results. However, fire resistance properties of specimens with coated aggregates presented that it has a lower thermal conductivity and internal temperature than the plain specimen. Especially, the specimen with coated aggregates was delayed at 17 min compared with the plain specimen on the increase of the internal temperature around 200 °C in the mortar. Therefore, it was confirmed that coated aggregates developed have an effect to decrease the internal temperature and delay time of the increase of the heat by reacting coating materials with heat.