# Mechanical Performance of Cement Bound Granular Mixtures Using Recycled Aggregate and Coconut Fiber
## 4 Conclusions  
The construction of pavement layers demands a significant amount of materials, particularly aggregates and, generally, natural aggregates (NA) are used. In this work, we evaluated the feasibility, in terms of mechanical performance, of using recycled aggregates (RA), mostly crushed concrete, derived from construction and demolition waste (CDW) and coconut fiber (CF) obtained from discarded coconut husk in the construction of cement bound granular mixture (CBGM). Such CBGM are commonly used in sub-base and base layers of road pavement. The use of RA and CF, obtained from actual waste materials, would enable savings in the consumption of non-renewable natural resources. Figure 6: Flexural strength of the CBGM at 28 days of curing. Figure 7: Example of CBGM specimens, without CF (**top**) and with CF (**bottom**), after the flexural strength test. An experimental program was developed in the laboratory to evaluate the mechanical performance of CBGM incorporating the abovementioned materials. The studied CBGM were tested for immediate bearing index (IBI), unconfined compressive strength (UCS), indirect tensile strength (ITS), and flexural strength (FLS). The obtained results highlight the suitability of RA for CBGM application and the potential of CF to provide a fiber reinforcement effect. Furthermore, the experimental results allowed the following conclusions:  
* Regarding immediate trafficking, the IBI results indicate good performance for all CBGM, underlining the suitability of RA to replace NA. * The mechanical performance tests--UCS, ITS, and FLS--revealed that the CBGM with RA presented a reasonably similar performance to the CBGM with high-quality NA, clearly indicating that the use of RA does not compromise the overall performance of the CBGM. Furthermore, notwithstanding the low cement dosages considered, 2% and 3%, all CBGM exceeded the usual minimum strength requirements set by the specifications of infrastructure administrations. * The use of CF promoted the effect of fiber reinforcement. However, in the cases of UCS and ITS, it did not have clear effects in the peak resistance of the CBGM. On the other hand, it effectively enhanced FLS at a higher cement dosage (3%). Generally, in all the tests, the use of CF maintained the integrity of the specimens at post-test. Furthermore, if compared to the CBGM without CF, the specimens of CBGM with CF presented minimal loss of particles and splitting during test loading and at post-test. Such an effect highlights the potential of CF to enhance the durability of the CBGM and its response under damaged (post-cracking) conditions. More studies are needed to quantify the effects on durability. For example, further studies will be conducted to evaluate durability following the mass loss due to brushing methods as indicated by AASHTO T 135 [60] and AASHTO T136 [61]. In addition, to better understand construction feasibility and in-service performance, the construction of a full-scale test section is ongoing. This test section will have different pavement stretches, using CBGM with NA and RA and without CF and with CF. Following construction, the bearing capacity will be periodically evaluated using falling weight deflectometer equipment. Conceptualization, J.C., L.P.-S. and J.N. ; methodology, J.C., L.P.-S. and J.N. ; validation, L.P.-S. and J.N. ; investigation, J.C. and L.P.-S.; data curation, J.C.; writing--original draft preparation, J.C.; writing--review and editing, J.C., L.P.-S. and J.N. ; project administration, L.P.-S. All authors have read and agreed to the published version of the manuscript. This research was funded by the Portuguese national funding agency for science, research, and technology (Fundacao para a Ciencia e a Tecnologia (FCT), I.P. ), under the Research Project PTDC/ECI-TRA/32244/2017. Not applicable.