# Ultrasonic Non-Destructive Testing of Accelerated Carbonation Cured-Eco-Bricks
## 5 Conclusions  
The CS of the samples produced in this study was examined using the UNDT and DT methods. From the experiments and analysis performed, the following conclusions can be made:  
1. UNDT utilizing P waves is recommended as a quicker and reliable testing method, as seen in the study.
2. ACC is a recommended curing option that is environmentally friendly and saves curing time.
3. LKD-GBFS can be combined in a 60:40 (LKD-GBFS) blending ratio to produce load-bearing bricks with a CS of 7 MPa for building small houses [54]. This can be achieved by carbonating the samples for a 72 hr period and exposing the samples to post-carbonation hydration for another 72 h.
4. TRC can be replaced with up to 5% to produce non-load-bearing bricks which can be used for constructing small houses [54]. This can be achieved by carbonating the samples for a 72 hr period and exposing the samples to post-carbonation hydration for another 72 h.  
Figure 16: Effect of curing time on CO\({}_{2}\) uptake for samples compressed with 1.9 MPa pressure.  
Figure 15: CO\({}_{2}\) uptake for 0% TRC samples.  
The maximum CS values for the 0% TRC samples were 3, 6, and 7 MPa for the HC, NWC, and WC approaches, respectively. This indicated a 100% increment in CS between the HC and NWC samples. Similarly, for the 5% TRC samples, maximum CS values of 2, 3.7, and 4 MPa were recorded considering the respective curing approaches mentioned above. This again indicated an 85% increment in CS between the HC and NWC samples. The results have shown that for the same 72 h curing durations, the carbonated samples had double the strengths recorded for the HC samples. This highlights ACC as a quicker curing approach that guarantees improved strength in a green way.
6. Further hydration after carbonation is recommended to enhance the significant formations of calcium carbonate (C-C), calcium silicate hydrates (C-S-H), and ettringite needles, leading to improved strength after carbonation.
7. This utilization of LKD as sustainable waste in construction will contribute to addressing the problems associated with the disposal of LKD in landfills. Additionally, using waste tire crumbs as alternative aggregates to replace natural sand partially will aid in reducing the pressure exerted on the natural resources and prevent their gradual depletion.
8. The total CO\({}_{2}\) uptake of the samples produced in this study was about 15,912 g (15.9 kg). This figure shows that there is potential for ACT to bring about the desired climate change.  
J.A.O.: Formal Analysis. J.A.O. and H.A.-N.: Conceptualization, Methodology, Writing--original draft. H.A.-N.: Supervision, Validation: J.A.O., and H.A.-N.: Writing--review and editing. All authors have read and agreed to the published version of the manuscript.  
This research was funded by the Tertiary Education Trust Fund (TETFund).  
Not applicable.  
The data presented in this study are available on request from the corresponding author. The data are not publicly available due to ethical.  
The first author wishes to acknowledge the Tertiary Education Trust Fund (TETFund) for sponsoring her studies at La Trobe University, Melbourne, Australia. Furthermore, the authors wish to express their keen appreciation to Cement Australia for the free LKD waste, and GBFS, samples that were donated to support the study. Lastly, the authors thank the La Trobe University Bioimaging Platform and thanks [PERSON] for microscopy support.  
The authors hereby declare that they have no conflict of interest.