Numerical Heat Transfer Analysis of Reduced-Dimension Masonry Walls under Fire Conditions

The evolution of numerical models has become a reliable, precise, and fast alternative to represent real physical phenomena and solve engineering problems. This is of special importance in fire resistance tests, which are notoriously expensive and complex to conduct under laboratory conditions. Thus, the main objective of this study was to perform a numerical analysis of heat transfer in masonry walls made of clay blocks and cement mortar (rendering and joint) under fire conditions. The performance evaluation criterion was heat insulation, as stated by standards. Masonry wall systems were modeled with four different block geometries, each with dimensions of 14cm×19cm×29cm. From geometric wall configurations, additional models with rendering mortar on the faces exposed and unexposed to fire, as well as constant or temperature-dependent thermal properties of the material were constructed. A mortar joint of 1 cm was considered in between the blocks and a rendering mortar of 2 cm was assumed on the exposed and unexposed faces. All models were exposed to fire for 4 h with the application of the ISO standard fire curve. After exposure, the temperatures on the unexposed side were measured and compared with the thermal insulation criterion limit. The models were validated with the results of the reference studies. The results indicated that the reduced-dimension masonry wall (RMW) with the most hollow spaces and the lowest net to gross area ratio (RMWA) had the best thermal performance. The rendering mortar significantly increased the fire resistance times: in the case of RMWA, the rendered wall reached an average temperature of 123°C in 4 h while the unrendered wall reached 164°C in 2 h 42 min.