ROCK WOOL

Rock wool is a type of mineral wool produced from a mixture of rocks such as basalt, diabase, and dolomite. Delivering perfect results in fire resistance and acoustic insulation, rock wool has lower values in thermal insulation as compared to plastic foams. Rock wool sandwich panels are used in roof, exterior wall, or partition coating in buildings with a high risk of fire. The insulating material is expected not to be directly affected by water. In addition, the thermal conductivity value of the materials should not increase indirectly through capillarity.

The fibers present in rock wool do not get wet; however, the air spaces between the fibers may fill up with water if they come in contact with water and the wet rock wool fails to function as an insulating material. For airborne-sound insulation, open pore materials (e.g., glass wool, rock wool, acoustic foam, etc.) are used. Sound absorbing materials are either porous or fiber materials and they exert their effect by transforming some portion of acoustic energy into thermal energy by causing friction losses in the air entering in the pores found in their structures. Contribution of rock wool sandwich panels to acoustic insulation is relatively better than other types of panels. On the other hand, high load bearing capacity values should not be expected from rock wool panels in case of conditions where high acoustic performance is required, and low-density rock wool should be used in such cases.

As a result of their internal structure, rock wool sheets have lower resistance values lengthwise as compared to widthwise. Nevertheless, its non-flammable properties have allowed for various activities to improve its low mechanical values. As a simple method, rock wool sheets are divided into lamella, in other words, they are cut into lines of desired thickness. This lamella is joined to create panels by using an adhesive. Therefore, mechanical properties are relatively improved while panels with high fire resistance are produced.

Mineral wools are quite stable materials as both fibers and bonding materials maintain their properties for a long period. Temperature has minimal effect on the mechanical properties of the material. Strength increases by an increase in density; however, it is more dependent on the internal structure. Compressive strength is between 0.005 and 0.08 N/mm2 for 60-150 kg/m3 limits. Tensile strength is low and typically between 0.001 and 0.01 N/mm2. The strength is higher in the direction of fibers. Similarly, shear strength varies between 0.03 and 0.20 N/mm2 based on the direction of fibers. In buildings where fire resistance is of critical importance, rock wool sheets consisting of inorganic fibers are used sandwich panel core material. Also defined as flammability capacity, fire resistance of the material is defined as fire performance. Fire resistance tests are carried out by a small-scale modeling of exterior wall and roof lines where the fire spreads the most in the building. Materials are categorized under 6 different fire classes beginning from A1 up to F. Other fire classes of the material are determined based on the amount of smoke and burning droplets due to fire. Rock wool sandwich panels deliver the best performance in fire-resistant exterior wall, roof, or interior partition wall applications.

Fire resistance of rock wool sandwich panels vary between 30 to 120 minutes depending on the type, thickness, and joint details of rock wool. Ignition temperature is 850°C. The structure of rock wool is open cell as compared to rigid foams. Open porosity structure of rock wool causes rock wool sheets to be more susceptible to water and vapor diffusion. However, this risk is minimized in sandwich panels due to metal surfaces that do not allow for diffusion.