*Article* **Predicting the Durability of Solid Fired Bricks Using NDT Electroacoustic Methods**

**Vojt ˇech Barto ˇn 1,\*, Richard Dvoˇrák 2, Petr Cikrle <sup>1</sup> and Jaroslav Šnédar <sup>1</sup>**


**Abstract:** Historical buildings and monuments are largely made of brickwork. These buildings form the historical and artistic character of cities, and how we look after them is a reflection of our society. When assessing ceramic products, great emphasis is placed on their mechanical properties, whilst their durability is often neglected. However, the durability or resistance to weathering of masonry elements is just as important as their mechanical properties. Therefore, this work deals with predicting the durability of solid-fired bricks before they are used when reconstructing monuments and historical buildings. Durability prediction is assessed by identifying defects in the material's internal structure. These faults may not be visible on the element's surface and are difficult to detect. For this purpose, non-destructive electroacoustic methods, such as the resonant pulse method or the ultrasonic pulse method, were used. Based on an analysis of the initial and residual mechanical properties after freezing cycles, four durability classes of solid-fired bricks were determined. This work aimed to find a way to predict the durability (lifetime) of an anonymous solid-fired brick, expressed in terms of the number of freeze cycles the brick would last, based on non-destructive measurements.

**Keywords:** solid fired brick; defects in the internal structure; non-destructive testing; resonant pulse method; material durability; machine learning
