# Durability of Mortars with Partial Cement Replacement by Recycled Brick Powder
## 2 Experimental Plan
### Methods  
The compressive strength of each mortar was evaluated in accordance with European Standard UNE-EN 196-1:2008 [76]. The test was conducted on six 40 \(\times\) 40 \(\times\) 40 mm cubic specimens using an Ibertest MEH-15005W testing machine. The loading rate was maintained at 2400 \(\pm\) 200 N/s throughout the entire load application until failure. Additionally, flexural strength was assessed following the specifications of UNE-EN 196-1:2008 [76]. This test was performed on three 40 \(\times\) 40 \(\times\) 160 mm prismatic specimens using an Ibertest IBMU-4 testing machine, with the load applied at a testing speed of 50 \(\pm\) 10 N/s until failure. In both cases, the reported results represent the average values obtained for each mixture. To evaluate the durability of the manufactured mortars, four distinct tests were conducted: water-accessible porosity, carbonation resistance, chloride diffusion resistance, and resistivity. Additionally, to assess the effectiveness of RBP as an SCM, its pozzolanic reactivity was analysed by measuring the pH and electrical conductivity in lime-pozzolana solutions. * Water-accessible porosity Firstly, a study of water-accessible porosity was conducted on three cylindrical specimens (100 mm in diameter and 50 mm in height). The test was performed in accordance with the specifications of UNE 83980:2014 [78]. Prior to testing, the specimens were over-dried at 105 \({}^{\circ}\)C until reaching a constant mass (M\({}_{\text{dry}}\)). They were then vacuum-saturated with demineralised water. After 24 h under these conditions, the post-vacuum saturated mass (M\({}_{\text{sat}}\)) and hydrostatic mass (M\({}_{\text{hyd}}\)) were determined for each specimen. The water-accessible porosity percentage (P) was calculated according to the formula specified in the test standard (Equation (1)). The result for each test and mix was taken as the arithmetic mean of the recorded values. \[P=100\ \times\left(M_{sat}-M_{dry}\right)/\left(M_{sat}-M_{hyd}\right)\] (1)
* Carbonation resistance For each manufactured mortar, carbonation resistance was also assessed, as it is a key parameter in material durability, affecting the time to reinforcement depassivation. This test was performed in accordance with UNE 83993-2:2013 [79] on three prismatic test specimens (40 \(\times\) 40 \(\times\) 160 mm). During the test, the specimens were subjected to accelerated carbonation in a chamber with a 3.00 \(\pm\) 0.6% CO\({}_{2}\) concentration (chamber conditions: 20 \(\pm\) 2 \({}^{\circ}\)C and 65 \(\pm\) 5% RH). After 7 and 28 days of exposure, the specimens were removed from the chamber and subjected to a flexural test to split them and determine the penetration depth by applying a phenolphthalein indicator to the internal surfaces. \begin{table}
\begin{tabular}{c c c c c c c c} \hline \multirow{2}{*}{**Ref. **} & \multicolumn{2}{c}{**\% RBP**} & \multirow{2}{*}{**CEM**} & \multirow{2}{*}{**RBP**} & \multirow{2}{*}{**Water**} & \multirow{2}{*}{**Sand**} & \multirow{2}{*}{**SP 1**} & \multicolumn{2}{c}{**Flowability**} \\  & & & & & & & **(mm)** \\ \hline C10 & 10 & 405.00 & 45.00 & 225.00 & 1350.00 & 4.700 & 120 \\ C15 & 15 & 382.50 & 67.50 & 225.00 & 1350.00 & 5.550 & 154 \\ C20 & 20 & 360.00 & 90.00 &  
The carbonation rate for each specimen (V\({}_{\text{CO2,3\%}}\)) was calculated according to the formula specified in the test standard based on the penetration depth (x) and exposure time (t) in years (Equation (2)). \[V_{\text{CO2,3\%}}=x/\sqrt{t} \tag{2}\]  
* Chloride diffusion resistance Chloride diffusion into the concrete is a major cause of reinforcement corrosion and was therefore included as a key parameter in this study. Since this is a slow process, laboratory studies commonly employ accelerated methods, such as the one described in European Standard UNE-EN 12390-18:2021, which determines the chloride migration diffusion coefficient (D\({}_{\text{nssm}}\)) [80]. This test was conducted on three cylindrical specimens (100 mm in diameter and 50 mm in height).