Improvement of Low Plasticity Clay with Crushed Glass: A Mechanical and Microstructural Study

Abstract

Low plasticity clays are found in abundance worldwide, exerting undue stresses on civil structures, road pavements and railway infrastructure, owing to the periodic settlement caused by their low bearing capacity and slight swelling potential. They are often encountered as natural soil when constructing road subgrade and have the potential to compromise the integrity of the entire pavement system unless improved appropriately. Furthermore, the accumulation of vast quantities of non-biodegradable glass waste is identified as a challenge in many countries. Considering the above, this paper aims to provide a sustainable solution by studying the effect of crushed glass (CG) at varied inclusions of 0, 5, 10, 15 and 20% in a clay subgrade. The testing procedure implemented includes three distinct testing phases, namely, material properties, microstructural properties and mechanical strength tests. The material property tests involved particle size distribution, X-ray fluorescence (XRF) and X-ray diffraction (XRD) testing. Microstructural tests considered include scanning electron microscope (SEM) and micro-CT (CT) testing, which enabled a vital understanding of how the introduction of glass affects the internal structure of the clay matrix, where an increase in the porosity was evident upon adding CG. The mechanical testing phase involved standard compaction, unconfined comprehensive strength (UCS), California bearing ratio (CBR), resilient modulus and swelling–shrinkage tests. It can be concluded that introducing CG improved the clay’s mechanical strength with respect to UCS, CBR and resilient modulus whilst also reducing its swelling potential, where the optimum inclusion of CG at 15% best enhanced the mechanical strength properties of the low plasticity clay.