# Feasibility of Non-Remanufactured Waste Bottle Glass as Supplementary Cementitious Material
## 4 Conclusions and Final Remarks  
The potential use of non-manufactured waste bottle glass as an SCM for concrete was investigated. Firstly, WG obtained from a local bottle industry was dried, sieved, and ground to obtain a PSD similar to cement. Since dry milling did not present reasonable results (GWG), wet milling followed (AGWG). Chemical and physical properties of WG and AGWG, as well as SEM observations, were carried out. In the second stage, mortar-level studies were performed, including WG and AGWG as a surrogate replacement, and mechanical behaviour and durability properties were evaluated. The main conclusions can be summarised as follows:  
* The main oxide composition revealed that WG consists mainly of SiO\({}_{2}\), CaO, and Na\({}_{2}\)O.
* A substantial decrease in mortar mechanical strength occurred when WG or AGWG were used as a 10% mass cement replacement.
* The mechanical strength of mortar, including 10% of incinerated waste glass powder, (WG700) achieved the REF mortar levels.
* Electrical resistivity was higher on glass-modified mortars, indicating the possibility of glass powder pozzolanic reactivity.
* The resistance against chlorides and capillary water absorption was similar among all mortars under study.
* ASR was reduced by over 30% in mortar specimens with 10% WG or AGWG as a cement replacement.  
The presence of fibres due to labels in recycled bottles seems responsible for the lower mechanical strength of mortars WG10 and AGWG10. A global analysis of the tests also showed that the WG mortars generally presented higher durability than those with the wet-milled material (AGWG) and even the REF mortars (excluding the carbonation test), implying that grinding may not be a solution to be considered. Given these results, the  
Figure 13: ASR expansion up to 28 ageing days.  
possibility arose of burning the material to eliminate the fibres and perform mortar strength tests to replace the incinerated material. Thus, finding the most eco-friendly and cost-effective way to treat WG is essential. Therefore, thermal treatment of WG may need to be incorporated in PC-based composites to deplete fibres and other contaminants. This will probably lead to a more successful application of this waste as an SCM for conventional concrete mixtures.  
Validation, A.M.M. and J.S.-C.; Formal analysis, A.M.M.; Data curation, A.M.M.; Writing--original draft, A.M.M.; Writing--review & editing, J.S.-C.; Project administration, A.M.M. and J.S.-C.; Funding acquisition, A.M.M. and J.S.-C. All authors have read and agreed to the published version of the manuscript.  
This work was financially supported as follows: Base Funding--UIDB/04708/2020 with DOI 10.54499/UIDB/04708/2020 ([[https://doi.org/10.54499/UIDB/04708/2020](https://doi.org/10.54499/UIDB/04708/2020)]([https://doi.org/10.54499/UIDB/04708/2020](https://doi.org/10.54499/UIDB/04708/2020))); Programmatic Funding--UIDP/04708/2020 with DOI 10.54499/UIDP/04708/2020 ([[https://doi.org/10.54499/UIDP/04708/2020](https://doi.org/10.54499/UIDP/04708/2020)]([https://doi.org/10.54499/UIDP/04708/2020](https://doi.org/10.54499/UIDP/04708/2020))) of the CONSTRUCT--Instituto de l&D em Estruturas e Construcoes; national funds through the FCT/MCTES (PIDDAC); and FCT--Fundacao para a Ciencia e a Tecnologia through the individual Scientific Employment Stimulus 2021.01765.CEECIND.  
Not applicable.  
The data presented in this study are available in the article.  
The collaboration and materials supplied by Secil and BA Glass Portugal are gratefully acknowledged. The authors especially thank Engineer [PERSON] for laboratory work support.  
The authors declare no conflict of interest.