Chemical stabilization of demolition wastes in pavement bases using one–part fly ash and slag based geopolymers

Abstract

The stabilization of road bases is a critical part of geotechnical research for developing new methods of sustainable road construction for the future. This study evaluated the feasibility of using one-part fly ash (FA) and slag (S) based geopolymers for stabilizing construction and demolition (C&D) aggregates with major significances including reduction in landfill wastes and lower carbon output to the environment. Furthermore, practical, environmental, and economic advantages of one-part geopolymer stabilized samples were addressed. In this study, the effects of parent aggregate types (including crushed brick, CB, recycled concrete aggregate, RCA, or reclaimed asphalt pavement, RAP), sodium hydroxide activator (ratios of 0.05, 0.1, and 0.2 by weight of precursor powders), precursor types (fly ash and slag) and precursor dosages (10 %, 20 % and 30 % by weight of parent materials) were evaluated. A series of geotechnical tests consisting of compaction tests, unconfined compressive strength test (UCS) at various curing conditions, repeated triaxial loading tests (RLT), and microstructural analysis were performed on the one-part geopolymer mixtures. The results indicated significant strength development at an activator ratio of 0.1 for CB and RCA and an activator ratio of 0.05 for RAP. Improvements in strength were seen in comparison to traditional geopolymers. All mixtures except for RAP + 10 % FA satisfied the minimum strength requirements but could be improved by allowing it to be cured for 28 days. Curing durations (7 days and 28 days), temperatures (20 °C and 40 °C), and activator ratios were found to influence the strength development of geopolymer samples. Resilient modulus (Mr) results showed that all selected geopolymer mixtures experienced good to excellent axial strain recovery behavior.