# Durability of Mortars with Partial Cement Replacement by Recycled Brick Powder
## 2 Experimental Plan  
### Materials  
To produce the mortars analysed in this study, 0/4 silica sand and CEM I 42.5 R/SR cement (Lafarge) were used. The recycled brick powder (RBP) was obtained by grinding ceramic bricks. This process was carried out in three stages. Each brick (7 cm hollow red brick) was manually crushed into fragments smaller than 50 mm, which were subsequently ground in a ball mill (model Ibertest Micro-Deval AIB-1250) in two cycles of 55,000 revolutions, each lasting 480 min. The resulting material was sieved with a 1 mm sieve. It was then subjected to a third grinding cycle lasting 30 min using a smaller mill (Speedy Nannetti model). The obtained powder was sieved again, this time with a 0.5 mm sieve. The final sample was analysed via laser diffraction using a Mastersizer 3000 (model MAL1203757). The recycled brick powder (RBP) exhibited a particle size distribution similar to that of cement, with an average particle size of 6.5 \(\upmu\)m, which is slightly smaller than that of cement (10.5 \(\upmu\)m). The particle size distribution curves of RBP and OPC are presented in Figure 1. Furthermore, Table 1 and Figure 2 provide detailed information on the chemical composition and the findings derived from the X-ray diffraction (XRD) analysis of the recycled brick powder, respectively.  
Figure 1: Grading curves: RBP and OPC.  
Table 2 presents the manufactured mixtures of the ten mortars produced using both the supplied cement and the RBP obtained through the grinding process. The nomenclature refers to the percentage of cement replaced with recycled brick powder. The reference mortar (C00) was prepared according to the mix proportions specified in the European standard UNE-EN 196-1:2008 for cement strength testing: one part cement, three parts standardised sand, and half a part water (1:3:0.5) [76]. In the remaining nine mix formulations, the cement was partially replaced with RBP in proportions ranging from 5% to 45%, while maintaining a constant water-to-cement ratio. To achieve a plastic consistency, a superplasticizer (Sika(r) ViscoCrete(r)--3425) was added to the reference mortar (C00). This admixture was also incorporated into the other mortars, with its dosage adjusted to maintain the same consistency. The reduced workability of mortars containing RBP was also reported by other authors [47; 48; 51] and is likely due to differences in shape and size between cement and RBP particles, as previously discussed. Table 2 also presents the fresh-state flowability results for each manufactured mortar, determined in accordance with the European standard UNE-EN 1015-3:2000 [77].  
Different test specimens were prepared with each of the previously described mortars to conduct this study. After casting, the specimens were kept in the moulds for the first 24 h, covered with plastic sheets for protection. They were then demoulded and stored in a curing chamber at 20 \(\pm\) 2 \({}^{\circ}\)C and a relative humidity above 95% until they reached 90 days of age, at which point the tests described below were performed.  
\begin{table}
\begin{tabular}{c c c c c c c c} \hline
**Ref.** & \
\begin{tabular}{c} **\% RBP** \\ **as Cement Substitute** \\ \end{tabular} & **CEM** & **RBP** & **Water** & **Sand** & **SP 1** &
\begin{tabular}{c} **Flowability** \\ **(mm)** \\ \end{tabular} \\ \hline C00 & 0 & 450.00 & 0.00 & 225.00 & 1350.00 & 3.375 & 126 \\ C05 & 5 & 427.50 & 22.50 & 225.00 & 1350.00 & 4.050 & 149 \\ \hline \end{tabular}
\end{table}
Table 2: Manufactured mixtures (kg/m\({}^{3}\)).  
Figure 2: X-ray diffraction pattern of RBP.