Enhancing The Geotechnical Performance Of Construction And Demolition Waste Through Alkali Activation For Sustainable Structural Fill Applications

Abstract

Without a doubt, construction and demolition (C&D) waste is one of the world’s biggest solid streams, however 
geotechnical potential of this material remains largely untapped. The research is an empirical study of the 
potential of alkali-treated C&D waste, consisting primarily of recycled concrete fines, brick aggregate, and 
mortar debris, to act as a structural fill material for geotechnical infrastructure. The waste was treated with three 
different alkali agents’ sodium hydroxide (NaOH), potassium hydroxide (KOH), and calcium hydroxide Ca(OH)₂ 
at varying concentrations (5–15%) and further binary blends using fly ash and ground-granulated blast-furnace 
slag (GGBS). Seven, fourteen, and twenty-eight day cured rocked treated and control specimens were prepared 
in the laboratory and laboratory tests were performed on the specimens including Proctor compaction, California 
Bearing Ratio (CBR), Unconfined Compressive Strength (UCS), consolidation, and heavy metals leachability test. 
The findings were indicated that the maximum dry density has increased, and the plasticity and load-bearing 
capacity has been ropped by the alkali activation. Results showed the combination of 10% NaOH+20%GGBS 
yielded the highest UCS (714.6 kPa) and soaked CBR (24.7%), corresponding to 473% and 550% improvement, 
over the raw C&D waste, respectively. The change in consolidation parameters was significant, and heavy metals 
leachability was found to be far below the USEPA limits. All treatment variables proved to be statistically 
significant by ANOVA (p < 0.001). The results set alkali-treated C&D waste as a promising, sustainable, and 
structurally appropriate geotechnical fill material.