Flexural strength is an important characteristic for each material. In this case, the resistance of the material is measured in relation to the maximum specific load, with constantly increasing pressure on the surface. Flexural strength is measured in Newtons per square millimeter (N/mm ^{2}).

Flexural strength is an important mechanical property of ceramic tiles, according to which its quality is controlled. On the one hand, this indicator determines the accuracy of the production process in achieving the desired degree of density and consistency of the material. On the other hand, it helps to determine the resistance of the tile, depending on the density of the material, under constant and dynamic pressure on the floor or wall surface. In order to fully appreciate the significance of this tile property and correctly apply the test results, it is necessary to clarify the following two concepts:

**Flexural strength is a property of the material, not the tile**. This indicator is used to measure the internal bonding properties of the material that forms the tile, rather than to measure a specific mechanical characteristic of the tile itself, such as the load-bearing capacity of the tile. Let's take, for example, two tiles made of the same material, but of different shapes and sizes. Suppose one tile is twice as thick as another, the flexural strength of these tiles will be the same, while the tensile strength of a thinner tile will be 3/4 less than that of a thicker one. Thus, the characteristics of the tiles differ, despite the fact that the flexural strength indicator is the same.**The tensile strength indicators, measured in accordance with the standards, in fact, as a rule, are inferior to the real load-bearing capacity of the tile, as an integral part of a multilayer structure such as a floor or wall**. Let us give an example of research from the Italian Ceramics Center in Bologna, which is based on complex calculations and test results. In this case, not only loads and pressure conditions are considered, but also actual limitations. Studies have shown that the load-bearing capacity of the tiled surface significantly exceeds, sometimes ten times, the forces required to break ceramic tiles acting on a separate tile not fixed to the tiled surface (we are talking about tests of tiles for bending strength in laboratory conditions).

Methods for determining flexural strength and breaking load are given in EN ISO 10545-4:1997 , IDT. Determination of the breaking force, breaking load and bending strength of a ceramic tile or slab by applying a force at a certain speed to the middle of the tile or slab, with the point of application of the force being in contact with the front surface of the ceramic tile or slab.

## There are 4 Comments

### Formulas for calculating bending strength

The breaking load S [H] is determined by the formula:

S = (F*L)/b, where

F - breaking force, [H]

L - distance between support rods, [mm]

b - width of the test sample, [mm].

Bending strength R, [N/mm ^{2} ], is determined by the equation:

R = (3*F*L)/(2*b*h ^{2} ) = (3*S)/(2*h ^{2} ), where

F - breaking force, [H]

L - distance between support rods, [mm]

b - width of the tested sample, [mm]

h - smallest thickness of the tested samples along the fracture line, [mm].

**Note** : To calculate the bending strength, a rectangular cross-section of the sample is taken. For tiles and slabs with different thicknesses along the failure line, only approximate values are obtained. More accurate values are obtained with a flatter sample profile.

- Login to leave comments

### Typical flexural strength values for ceramic tiles

The flexural strength values depend on the type of ceramic tile and are determined according to the methodology outlined in the ISO 10545-4 standard.

For floor tiles with a water absorption of 0.5 < E < 3%, the flexural strength must be more than 30 N/mm2.

For wall tiles with water absorption E > 10%, the flexural strength must be more than 15 N/mm2.

For porcelain stoneware E <= 0.5%, the bending strength must be more than 35 N/mm2.

The actual values of the bending strength of ceramic tiles are higher. So, for example, if we take Kerama Marazzi products, we get the following values:

For floor tiles with water absorption 0.5 < E < 3% - 39 N/mm2;

For wall tiles with water absorption E > 10% - 20 N/mm2;

For ceramic granite E<= 0.5% - 55 N/mm2.

- Login to leave comments

### Dependence of ultimate strength on thickness

Do I understand this proposal correctly?

Suppose one tile is twice as thick as another, the flexural strength of these tiles will be the same, while the tensile strength of a thinner tile will be 3/4 less than that of a thicker one.

In other words, the tensile strength of a thinner tile will be 4 times less than that of a thicker one.

- Login to leave comments

### Dependence of ultimate strength on thickness

Yes, that's right. The breaking force, as well as the breaking load, are directly proportional to the square of the thickness of the ceramic tile. Therefore, doubling the thickness of the tile increases the breaking force and the breaking load by four times.

- Login to leave comments