# Durability Assessment of Eco-Friendly Bricks Containing
## 4 Tests Carried Out on the Bricks  
Tests carried out on the bricks included the following:  
* **Compressive strength (CS) test** A compression test is usually carried out to ascertain the peak stress that any sample can withstand. The compression test was carried out using the MTS compressive strength testing machine. The testing machine comprises two flat steel plates: one in a firm position, upon which the masonry unit was placed, while the other is a movable plate, which was responsible for transmitting the load to the sample when the load was applied. The plates were arranged in such a way that the centroid of the masonry unit coincided with the center of the plate thrust. The load was applied at a uniform rate of 4 mm/min, and the load that caused the failure in the masonry unit was noted. For each TRW content considered, three samples were tested, and their average compressive strength was computed. The testing procedure was carried out in line with codes [48; 49; 50], and the CS was computed using Equation (1) below, as required by AZ/NZ-4456.4- [50]: \[\text{CS}=\frac{K_{a}\ (1000P)}{A}\] (1) where \[K_{a}=\text{Aspect ratio factor determined by the height-to-thickness of the brick;}\] \[P=\text{Load that caused failure of the brick (kN);}\] \[A=\text{Area of the brick (mm}^{2});\] \[\text{CS}=\text{Computed compressive strength (MPa).}\]  
Figure 2: Samples wrapped with nylon film. * **Flexural strength (FS) test** An FS test is usually carried out on bricks to assess their ability to withstand bending or flexural stress. It is carried out to investigate the structural integrity and breaking resistance when a load is applied to a brick. The information from an FS test is crucial for engineering and construction applications, ensuring that the bricks tested meet the required strength for construction purposes. The samples that were cured for 7, 14, and 28 days were set up as shown in Figure 3 a,b and tested according to codes [51]. The loading rollers were brought into contact with the top of the brick sample, and then a seating load that did not exceed 100 N was applied to the brick sample. The uniformity of the bearing of the rollers was checked, and their positions were marked on the sides of the bricks, as shown in Figure 3, before proceeding with the loading. The samples were loaded at a constant rate of 0.3 mm/min until they fractured (failure occurred), and the modulus of rupture was calculated using Equation (2) below, as required by codes [51]:  
\[f_{cf}=\frac{PL(1000)}{BD^{2}} \tag{2}\]  
where \(f_{cf}\) = Flexural strength (MPa); \(P\) = Maximum applied force indicated by the testing machine (kN); \(L\) = Span length (mm); \(B\) = Average width of the specimen at the section of failure (mm); \(D\) = Average depth of specimen at the section of failure (mm). It was important to note that the fractures did not occur outside the middle third of the span length (indicated with blue lines, as required by code AS 1012.11) [51]. Figure 3 shows the brick samples before and after testing using the MTS testing machine, showing that the fracture occurred within the middle third of the span. * **Freeze-thaw (F-T) test** F-T tests are usually performed to estimate the resistance and durability of a concrete sample to resist deterioration when exposed to repeated freeze-thaw cycles [48]. This is because F-T is considered to be one of the durability properties of bricks and has been identified as one of the major factors in brick degradation [52; 53; 54]. It has also been established as a qualitative and direct method used to assess the durability of bricks [52; 53; 54]. Furthermore, it has been reported that bricks are porous building materials that usually contain some amount of moisture within their structure. This moisture has a direct influence on the bricks' properties such as shrink and expansion, strength, resistance to external conditions, and vapor permeability [55]. The durability of the bricks was tested by assessing their resistance to F-T, as described in code EN 772-22 [56].