# Assessment on the Properties of Biomass-Aggregate Geopolymer Concrete
## 4 Conclusions  
The purpose of this study was to study the preparation of SBRA from agricultural by-product coconut shell and to evaluate the mechanical properties, thermal conductivity, and economic performance of SBRAC. Based on the above research results, the following conclusions can be drawn:  
1. When the water-to-binder ratio is about 0.25, the cement slurry can better adhere to the surface of the crushed coconut shell and finally form the SBRA, whose shape tends to be oval, and the aggregate gradation is good. The SBRAC prepared by mixing crushed coconut shell and cement slurry has good volume stability. The 3 days and 28 days compressive strength values of SBRAC reach 91.9% and 86.6% of NAC, respectively. 2. Compared with CCSAC, the attached mortar shell structure on the surface of SBRA effectively maintains the volume stability of coconut shell aggregate and reduces the self-shrinkage of concrete. However, compared with natural aggregate concrete, the self-shrinkage rate of synthesized biomass recycled aggregate concrete (NAC) is relatively high, generally around 800 \(\times\) 10\({}^{-6}\), which is higher than 400 \(\times\) 10\({}^{-6}\), that of NAC. 3. SBRA can effectively reduce the thermal conductivity of concrete, and the thermal conductivity of SBRAC is lower than that of wall materials such as ordinary concrete and clay bricks, which means that SBRAC has a greater potential for building energy savings. 4. Under the same volume, the cost of CCSAC and ABRAC reached 74.9% and 95.2% of that of RAC, respectively; and, at the age of 28 days, the compressive strength-cost ratio of CCSAC and ABRAC reached 93% and 92% of NAC, respectively, which indicates a cost-friendly concrete. 5. The use of SBRA to completely replace NA did not cause the significant attenuation of concrete performance, but the shrinkage performance and cost of SBRAC still have potential for further optimization, and how to effectively reduce the cost of use and improve the shrinkage performance are key factors in the application of SBRAC. Figure 9: (a) Cost ratio of concretes. (b) Compressive strength–economic efficiency. **Author Contributions:** Investigation, methodology, formal analysis, data course, and writing--original draft preparation, H.L. ; project administration, conception, and funding acquisition, Q.L. ; writing--review and editing and software, H.Q. ; resources, visualization, X.X. ; validation, Q.W. ; writing--review and visualization, S.N. All authors have read and agreed to the published version of the manuscript. **Funding:** This research was funded by the National Natural Science Foundation of China, grant number 52078261. **Institutional Review Board Statement:** Not applicable. **Informed Consent Statement:** Not applicable. **Data Availability Statement:** Not applicable. **Acknowledgments:** The authors gratefully acknowledge the financial support of Project Numbers 52078261 from the National Natural Science Foundation of China, Development and Application of Biomass Artificial Reef (20220035). **Conflicts of Interest:** The authors declare no conflict of interest. * [PERSON] et al. (2021) [PERSON]; [PERSON] [PERSON]; [PERSON]; [PERSON]; [PERSON] Study of various properties of geopolymer concrete--A review. _Mater. Today Proc._**2021**, _46_, 5687-5695. [CrossRef]
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