Development of Sustainable One-Part Alkali-Activated Binders Derived from Construction and Demolition Waste ("Just Add Water" Approach)

Ankara University, Department of Civil Engineering, Faculty of Engineering, 06590 Ankara, Turkey

^* Corresponding author: hulugol@ankara.edu.tr

Abstract

This study investigates the effect of alkali concentration on the mechanical performance of one-part alkali-activated binders produced using construction and demolition waste (CDW) as a precursor material. Four different alkali concentrations (0.30, 0.35, 0.40, and 0.45) were applied in mixtures where the alkali-to-binder ratios were 0.22, 0.26, 0.30, and 0.35, respectively, and the water-to-binder ratios were adjusted between 0.51 and 0.42. The sand-to-binder ratio was kept constant at 2.2 for all mixtures. Results revealed that increasing alkali concentration improved the reactivity and strength development of both brick and concrete waste-based binders. The highest compressive strength values were obtained at an alkali concentration of 0.45 for both waste types, indicating enhanced polymerization and matrix densification at higher activator levels. Unlike traditional geopolymer systems requiring the preparation of alkaline solutions, this binder can be easily produced by simply adding water to the dry mix, providing a practical and user-friendly approach for field applications. The findings demonstrate that the use of CDW as a cement-free binder not only provides satisfactory mechanical performance but also offers a sustainable alternative to conventional cement, contributing to environmental conservation and green transition in construction.