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

Abstract

In the context of sustainability in the civil engineering industry, chemical ground improvement is becoming increasingly used, as a generally more sustainable alternative to replacing and landfilling unsuitable for construction ground. However, traditional soil stabilisers such as Portland cement or lime are not environmentally impact-free; international research effort is thus focusing on the development of innovative cementing agents. This paper presents results from a feasibility study on the development of suitable alkali-activated slag cements for the stabilisation of two soils. A number of alkali-activators were considered, comprising potassium hydroxide, a range of alkali salts, as well as a material retrieved from waste (Paper Sludge Ash, PSA) which contains free lime. Indicative results of an extensive parametric study in terms of unconfined compressive strength (UCS) are shown, followed by results of ongoing oedometer tests to determine soil compressibility and some preliminary tests on selected soil/binder mixes to observe the durability to wetting-drying cycles. Overall, all alkali-activated cement mixes increased the UCS and stiffness of the soil. Carbonates and Na2SiO3 used on their own gave lower strength increases. The highest strengths were achieved from AAC with KOH and Ca(OH)2 from PSA, which showed similar strength gain. The latter material has shown consistently a lot of promise in terms of strength, stiffness and volumetric stability of the soil as well as treatment durability. Ongoing research focuses on further mix optimisation and a comprehensive mechanical and durability property testing supported by material analysis (mineralogical, chemical and microstructural) to gain a better understanding of the complex mechanisms involved.

A Review of Advances in Peat Soil Stabilisation Technology: Exploring the Potential of Palm Oil Fuel Ash Geopolymer as a Soil Stabiliser Material

“…Since the introduction of the use of geopolymers as a cementitious binder to the engineering research community by Davidovits [72] and Duxson et al [73], the use of geopolymers for soil stabilisation purposes has also gained attention in recent years. The emergence of geopolymer applications to enhance the engineering properties of weak soils has proven its benefits to the geotechnical research community [74][75][76]. Abdullah [77] summarised the engineering benefits of using geopolymers to remediate the inherent weaknesses in problematic soils: (1) enhanced soil structure due to the synthesis of cementitious gels created in the soil voids; (2) increased strength of the soil matrix as the presence of geopolymer material improves the shear stress resistance of the stabilised soil.…”

An electrokinetic-biocementation study for clay stabilisation using carbonic anhydrase-producing bacteria

“…Traditional methods of chemical ground improvement include the addition of small percentages of Portland cement (Yoobanpot et al 2017 ) or lime (Ghorbani et al 2019 ; Kichou et al 2022 ; Zhang et al 2015a , b ) and also fly ash (Abdullah et al 2020 ; Deepak et al 2021 ). Recent options include more innovative cements such as alkali-activated cements/geopolymers (Ghadir and Ranjbar 2018 , Mavroulidou et al 2022 , 2023 ) or biocements, produced by the metabolic actions of microorganisms through various processes, including ureolysis (Omoregie et al 2021 ; Phillips et al 2013 ), photosynthesis (Irfan et al 2019 ), denitrification (Jain et al 2021 ; O’Donnell et al 2017 ), and methane oxidation (Ganendra et al 2014 ). This paper proposes instead the carbonic anhydrase metabolic pathway, as an innovative eco-friendly and sustainable soil stabilisation method, which can consume captured waste CO 2 or CO 2 from the atmosphere to precipitate CaCO 3 which binds together (biocements) soil particles.…”

Geotechnical Properties of Soil Stabilized with Blended Binders for Sustainable Road Base Applications

“…Previous studies have indicated that the addition of various stabilizing agents improved the workability of soils [9][10][11][12][13]. For instance, adding cement improves the strength and bearing capacities of soils [14], while adding lime contributes to gain in strength in tested soil specimens [15].…”