Towards the Development of Sustainable Ground Improvement Techniques—Biocementation Study of an Organic Soil

Abstract

Ongoing research effort is dedicated to the development of innovative, superior and cost-effective ground improvement techniques to mitigate natural and man-made hazards while minimising waste and other environmental impacts. In this context, the nature-based process of biocementation of soils has been proposed as a potentially more sustainable technique than conventional chemical ground improvement practices. This paper focuses on the biocementation of an organic soil of the UK railway network. Having recently proven the feasibility of biocementing this soil using indigenous ureolytic bacteria, in this paper, the authors perform a parametric study to identify treatments successful in increasing the strength of the soil. Selected treatments are then applied to the soil to assess its volume change during consolidation, secondary compression and shrinkage upon drying. The results show that, depending on the treatments used, biocementation has increased the unconfined compressive strength by up to 81% compared to that of the control samples. For selected treatments and the range of water contents tested (55–33%), shrinkage upon drying reduced by 16%, while the volumetric strains of the soil upon 1-D compression reduced by 32–47%. This was reflected in the values of the coefficient of volume compressibility and the coefficient of secondary compression (the latter either reduced by up to an order of magnitude or secondary compression was not observed altogether in the testing period). Overall, the results proved that biocementation improved considerably the mechanical properties of the organic soil, which gives promise for addressing the settlement problems of this soil.

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

“…The newly isolated carbonic anhydrase bacteria identified as Bacillus licheniformis were used for bioaugmentation. As stated in Safdar et al ( 2022 ), the American Type Culture Collection (ATCC) classifies the isolated strain as of Biosafety Level (BSL) 1 (i.e. not known to consistently cause disease in healthy adults, and of minimal potential hazard to laboratory workers and the environment), and similarly, the BacDive database for standardised bacterial information classifies the strain into Risk group 1 (biological agents which are unlikely to cause disease in an individual) according to the German Federal Institute for Occupational Safety and Health.…”

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

“…GGBS is now a widely used by-product and an established commercially supplied low-cost supplementary cement material (SCM) in blended Portland cements for concrete. GGBS AAC systems for concrete have been shown to have good durability, for instance against sulphate or acid attack, and other chemically aggressive environments [44,48,49]; for ground improvement GGBS has been used in blends with calcium-based soil stabilisers to counteract effects of sulphate-induced heave [50]. There is therefore good potential for the use of GGBS in AAC if the right AAC system is chosen.…”

“…2(b) and 3(a) KOH used as the sole activator at the same percentage as PSA led to higher earlier strengths than PSA. However, after 28 days of curing, PSA activator mix strengths were very close-in several occasions higher-to those of the respective KOH mixes; the latter showed little strength evolution between 7 and 28 days; conversely PSA mixes kept gaining strength in time (this was not expected as according to the Authors' experience, PSA used as an alkali activator of GGBS in concrete cement [43,44] gave instead high early strength gain with less strength evolution in later times; this could however be due to the relatively low PSA content used in the concrete mixes). The strength gains with only 3 to 6% PSA in the mixes were very considerable, namely, (a) for mixes without Na 2 SiO 3 17-20 and 30-60 times higher than that of silt for 7 and 28 days of curing respectively; (b) for mixes with PSA+Na 2 SiO 3 22-62 and 66-74 times higher that of silt for 7 and 28 days of curing respectively.…”

“…Alternative cementing materials are therefore actively sought, towards low-carbon, sustainable engineering solutions, contributing to the achievement of UN sustainable development goals (see e.g. [2]); the potential of using waste materials in the alternative cementitious binder composition is also targeted, to address solid waste management and transform waste to an opportunity, while reducing energy consumption, CO 2 emissions and raw material use. In this context, alkali-activated cements (AAC) are emerging as promising candidates to replace traditional cements and are expected to be a key component of a sustainable future global construction materials industry [3].…”

Effect of bio-cementation process on sandy soil

“…To assist the MICCP process in geo-technical engineering practices, a large scale analysis of MICCP applications are recommended [18]. In general, the outcome proved the capability of bio-cementation to amend considerably the different features of the sandy soil, even for a minor amount of cementation; this is used asan alternative for accessing the settlement property of this sandy soil [19]. The findings demonstrate that significant binding in loose sand soils may be produced by controlling and manipulating natural microbial processes.…”