# Mechanical Performance of Cement Bound Granular Mixtures Using Recycled Aggregate and Coconut Fiber
## 2 Materials and Methods  
### Materials  
The materials required for the production of conventional CBGM are aggregates, cement, and water. The variables under study were the type of aggregate and the incorporation of CF to promote a reinforcement effect. To isolate the effects of these variables, the same cement and water source (tap water) were used throughout the experimental program. In total, six CBGM were studied, according to the compositions indicated in Table 1. In Table 1, the cement and the CF dosages are given as a percentage of dry aggregates mass and as a percentage of dry solids mass (cement and aggregate), respectively. Two types of aggregates were used: one NA and one RA. Table 2 presents the particle size distribution of the aggregates and the grading envelope indicated by the Portuguese infrastructure agency for the aggregate 0/31.5 to be used in CBGM [44]. The RA was obtained by processing CDW through a jaw crusher. Regarding lithology, the original aggregate of the RA was mainly derived from grandoiorite. The RA can be classified according to its constituents. According to EN 933-11 [45], which establishes a classification for the constituents of coarse RA (\(\geq\)4 mm), the constitution of the RA was: 81.0% concrete, concrete products, and mortar; 18.3% unbound aggregate, natural stone, and hydraulically bound aggregate; 0.3% clay masonry, calcium silicate masonry, and aerated non-floating concrete; and 0.3% bituminous materials. For instance, under the AASHTO framework [46], this RA would classify as reclaimed concrete aggregate (RCA). Table 3 presents the properties of the NA and RA. The Portuguese specifications [44] set a maximum of 30 and 40 for the flakiness index and Los Angeles coefficient, respectively. The specifications also indicate that when the percentage of fines is higher than 3%, the sand equivalent should be higher than 50. If the percentage of fines is higher than 3% and the sand equivalent is lower than 50, methylene blue must be lower than two. Finally, if the percentage of fines is lower than 3%, the characteristics of the fines are considered irrelevant to the general performance of the aggregate mixture. Thus, both aggregate types match the requirements of the specification. Regarding the RA, the higher Los Angeles abrasion and water absorption can be partially explained by the residual adhered mortar. Other authors also identified higher Los Angeles abrasion and water absorption of RA [10; 17; 20; 47]. \begin{table}
\begin{tabular}{c c c c} \hline
**CBGM Designation** & **Type of Aggregate** & **Cement Dosage** & **CF Dosage** \\ \hline NA\_2\_0 & Natural & 2\% & 0\% \\ NA\_2\_0.1 & Natural & 2\% & 0.1\% \\ RA\_2\_0 & Recycled & 2\% & 0\% \\ RA\_2\_0.1 & Recycled & 2\% & 0.1\% \\ RA\_3\_0 & Recycled & 3\% & 0\% \\ RA\_3\_0.1 & Recycled & 3\% & 0.1\% \\ \hline \end{tabular}
\end{table} 
Table 1: Designation and constituents of the six CBGM compositions studied. \begin{table}
\begin{tabular}{c c c c c} \hline  & \multicolumn{4}{c}{**Cumulative Percent Passing**} \\ \cline{2-5}
**Sieve of Square** & \multicolumn{2}{c}{**Type of Aggregate**} & \multicolumn{2}{c}{**Specification Limits**} \\ \cline{2-5}
**Aperture (mm)** & **NA** & **RA** & **Minimum** & **Maximum** \\ \hline
40 & 100 & 100 & 100 & 100 \\
31.5 & 97.4 & 96.1 & 80 & 99 \\
16 & 72.8 & 75.5 & 63 & 77 \\
8 & 55.1 & 51.8 & 43 & 60 \\
4 & 38.3 & 36.7 & 30 & 52 \\
2 & 24.6 & 25.8 & 23 & 40 \\
1 & 15.6 & 19.6 & 14 & 35 \\
0.5 & 11.0 & 13.9 & 10 & 30 \\
0.063 & 2.8 & 4.0 & 2 & 7 \\ \hline \end{tabular}
\end{table} 
Table 2: Aggregate particle size distribution and specification limits used as reference. In all mixtures, the cement used was Portland CEM II/A-L 42.5 R. This type of cement was selected because it is the one most used by the Portuguese industry. Aligned with the objective of reducing the consumption of natural resources, low cement dosages (2% or 3%) were used throughout the study.