A comparative assessment of chemical stabilisers including waste materials, for the treatment of swelling-shrinking soils

Abstract

This paper assesses comparatively the performance of a number of innovative soil stabilisers for the treatment of a highly swelling-shrinking soil, against that of commercial calcium lime. The production of lime, a most common soil stabiliser, involves high energy consumption, carbon dioxide emissions and the depletion of natural raw materials. Alternatives are actively sought, in particular industrial wastes and by-product materials or lower energy demand cements e.g. reactive magnesia (MgO) cements. In this paper calcium lime, reactive magnesia, industrial wastes and mixes of these with lime are comparatively assessed, based on a number of conventional measures of the propensity of a soil to swell, i.e. plasticity characteristics and swelling characteristics (swelling strains, swelling pressures, swelling indices). Furthermore, as expansive soils are typically in an unsaturated state hence sensitive to both changes in water content and suction, filter paper testing was performed to provide additional evidence of the effect of the treatments on the swelling/shrinking soil. According to the main findings, for the treatment of swelling shrinking soils, binders coming from the paper recycling industry show most promise as alternatives to lime; reactive magnesia cement had a smaller effect than calcium based stabilisers in improving the swelling-shrinking of the soil, yet it also suppressed swelling and shrinkage considerably; it thus shows potential for use as an alternative to common soil stabilisers (Portland cement and calcium lime) to alleviate the environmental impact of the latter.

A Study of Innovative Alkali-Activated Binders for Soil Stabilisation in the Context of Engineering Sustainability and Circular Economy

“…In the UK, the increasing amount of PSA classified as waste (with 4 out 40 paper mills reported to generate 140 ktonnes of PSA annually [38,51]), has caused environmental concerns and high costs to industry due to UK landfill tax (£96.70/t and £3/t for active and inactive waste respectively in 2021). PSA has shown great promise as an alternative to lime for soil stabilisation [35,45,52,53]. Here, its good performance in alkali activator mixes was also proven, as it led to early strength gains, continued increase in strengths upon curing, comparable to other established and more caustic activators such as KOH, and showed the best durability to wetting-drying.…”

“…The very good overall performance of the PSA is consistent with a number of previous studies by the Authors, where the material was used either as an activator of GGBS or otherwise fully or partially replacing cement or lime. PSA led to similar or better strengths than cement or lime for a number of soils, in particular different clays, silt and the paper sludge itself (from which PSA originates) which could then be used as a fill material instead of soil [35,45,52,53].…”

Properties of structural concrete with high-strength cement mixes containing waste paper sludge ash

“…A number of possible applications of WPSA in construction have been studied but there are relatively few works on each particular application. WPSA was proven an efficient soil stabiliser for geotechnical applications as an alternative to OPC or lime [6,[8][9][10][11][12], including also the possible valorisation of the wastepaper sludge itself stabilised by WPSA, as a fill material for construction [13]. The successful use of WPSA in activator mixes of alkali-activated cements (AAC) for ground improvement was also demonstrated [14,15].…”