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Recycling of unseparated construction and demolition waste (UCDW) through geopolymer technology

Tijdschriftbijdrage - Tijdschriftartikel

Geopolymer technology has been recognized as an ideal option for recycling construction and demolition waste (CDW) streams as new value-added products. However, most research efforts have been devoted to the geopolymer derived from the individual fraction separated from CDW. Given the technological complexity presented in separating CDW fractions on a commercial scale, using unseparated CDW (UCDW) in geopolymer application can achieve higher environmental and economic benefits. This paper investigated the feasibility of using UCDW consisting of various constituents, i.e., unbound aggregates (UA), red clay bricks (RCB), waste concrete (WC), waste glass (WG), and waste tiles (WT), in geopolymer production. The effects of these constituents on the reactivity of UCDW and the performance of the resulting geopolymer paste were studied. Results showed that all UCDW constituents can provide reactive phases and highly reactive bonds. RCB, WG, and WT can serve as the aluminosilicate source, while UA and WC mainly offer silica and calcium. The changes in constituents affected the mechanical performance of the UCDW-based geopolymer by conditioning the content of reactive Si, Al, and Ca in the precursor. A Si/Al molar ratio of 5–8 and a Ca/Si of 1.5 were found to achieve the higher compressive strength (up to 29.7 MPa) of geopolymer. In addition, a fitting formula was proposed to predict the compressive strength of UCDW-based geopolymer paste. This work contributes to understanding the alkali-activated performance of UCDW and promotes its utilization as a mineral precursor in geopolymer production.
Tijdschrift: Construction & Building Materials
ISSN: 0950-0618
Volume: 341
Pagina's: 1 - 13
Aantal pagina's: 13
Jaar van publicatie:2022