Circular economy approach to geopolymer development using construction and demolition waste

Creative Commons License

İLCAN H., Sahmaran M.

Journal of Construction Engineering, Management & Innovation (Online), cilt.9, sa.1, ss.1-8, 2026 (ESCI, TRDizin)

Özet

This study investigates the construction and demolition wastes (CDWs) valorization in geopolymer production under various conditions, emphasizing the criticality of reutilizing CDWs in a value-added manner. The CDW-based precursors used in this study were red clay brick (RCB), hollow brick (HB), roof tile (RT), glass waste (GW), and concrete waste (CW), along with blast furnace slag (BFS) as an industrial by-product. Recycled concrete aggregate (RCA) was employed as an aggregate, while sodium hydroxide (NaOH) used as the sole alkaline activator at varying dosages to activate the precursors. The influence of NaOH molarity, the form in which NaOH is added (solution, powder, or flakes), and precursor blends were evaluated by conducting flow table and compressive strength tests, alongside a cost comparison to analyze the effects of these parameters on economic performance. The results indicated that increasing the NaOH molarity improved both workability (~ 5%) and compressive strength (~ 95%), which can be attributed to the enhanced dissolution of aluminosilicate species and the subsequent geopolymerization reaction. CDW-based geopolymer mixtures reached compressive strengths ranging from 10 to 25 MPa after 28 days of ambient curing. Among the precursors used in this study, masonry-based precursors exhibited superior performance, particularly the HB samples, which demonstrated the highest mechanical performance. The method of NaOH addition had no noticeable influence on the engineering properties of the CDW-based geopolymer mixtures activated by solely 4M NaOH. Cost analysis showed that the alkaline activator, BFS content, and transportation expenses were the major factors to overall costs. The HB-containing mixture showed superior performance both in terms of cost per cubic meter and cost per 1 MPa, compared to other CDW-based precursors. Although the 100% BFS-based geopolymer mixture had a higher cost per cubic meter, its cost per MPa was slightly lower and comparable to that of the HB-containing mixture. This study provides insights to guide experimental design and support future research on sustainable waste-derived binder systems.