Sustainable stabilization of highly sensitive clay by using recycled crushed concrete

¹ Porelab, Department of Civil and Environmental Engineering, Norwegian University of Science and Technology (NTNU), Trondheim, Norway
² Norwegian Geotechnical Institute (NGI), Trondheim, Norway

^* Corresponding author: This email address is being protected from spambots. You need JavaScript enabled to view it.

Abstract

Highly sensitive clays possess a unique metastable structure that can undergo strength loss when subjected to loading or vibration. In regions containing these clays, major challenges to infrastructure development arise, necessitating extensive ground improvement. The conventional applied ground improvement method for these clays is dry deep-mixing of binders like cement and lime, which are highly CO2 intensive materials. This study investigates the use of recycled crushed concrete (RCC) as a more environmentally friendly alternative for stabilizing highly sensitive clay, in combination with zeolite and quicklime. Zeolite was selected as a pozzolanic material and a source of SiO₂ and Al₂O₃, while quicklime was used to supply Ca²⁺ ions and increase pH to promote pozzolanic reactions. RCC was employed as both a pozzolanic material and a calcium source to reduce the consumption of natural resources. RCC was used in powdered, coarse-grained, and well-graded forms to evaluate the combined effects of chemical and mechanical stabilization. Specimens were tested after 7, 14, and 28 days of curing using unconfined compressive strength tests and X-ray diffraction analysis. The optimum mixture consisted of 50 kg/m³ of zeolite and quick lime and 25 kg/m³ of powder RCC. The primary cementitious products identified were calcium-silicate-hydrate and monocarboaluminate.