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Geomaterials: from Waste to Resource

Periodic Reporting for period 1 - GeoRes (Geomaterials: from Waste to Resource)

Reporting period: 2018-03-01 to 2020-02-29

Geomaterial waste represents half of the total waste volume generated in EU-27. In general, these waste geomaterials exhibit poor engineering characteristics and/or specific mineralogical composition that prevent their direct reuse on construction/mining sites. However, if adequately treated, they could represent an excellent resource for construction projects with significant money saving and reduction in the environmental footprint, thus contributing to the establishment of a circular economy.
To achieve this, the GeoRes Project aims to develop innovative solutions for the reuse of waste geomaterials generated by construction and mining industries across Europe and worldwide. This involves development of protocols to improve the engineering characteristics of waste geomaterials, and to guarantee the level of performance over the service life of geo-structures built from waste geomaterials considering site-specific conditions (climate, water table, leaching, weathering, hazardous compounds, etc.). The fundamental concern of the research in the GeoRes network is thus to develop strategies and tools for sustainable reuse of waste geomaterials generated by geoengineering activities, and to determine how to turn a waste geomaterial into a valued durable material, with a positive revenue stream.
The GeoRes project has progressed according to the plan. Test sites have been identified and the waste geomaterials to be used have been selected for testing the mechanical and transfer properties. Several soils were selected in order to cover a wide range of plasticity index, and to be representative of a variety of contexts. For the stabilisers, standardised products like lime or cement, and also stabilisers containing large amounts of by-products from industry were considered.

Progress in different work packages:

WP1: Mechanical behaviour of treated waste-geomaterials

WP1 is primarily focused on the durability of the mechanical performances of upgraded waste-geomaterials as a function of the context, site conditions, climate, etc. The goal of WP1 is to uncover the key mechanisms which control alteration of mechanical properties of upgraded waste-geomaterials in several contexts. The first step of the implementation of the project was the identification and selection of soils, stabilising agents and test sites. An analysis of existing data on a limited number of materials and sites, based on the experience of each partner, was accomplished. Several actions have then been defined, each connected to a given context of application / type of material. The actions in progress are connected to:
1. Impact of wetting and drying cycles.
2. Behaviour of lightweight cemented soils.
3. Multiphysical couplings in compacted and treated unsaturated soils.
4. Thermo-hydro-mechanical interaction between the climate and geomaterials.
5. Study of behaviour of fine-grained soil stabilised by fly ash and alkali activators.

WP2: Durability of transfer performance of treated waste geomaterials

The goal of WP2 is to uncover the key mechanisms which control alteration of transfer properties of upgraded waste-geomaterials in several contexts in order to develop general recommendations and guidelines to promote durability of transfer properties of upgraded waste geomaterials. The first step of the implementation of the project was the identification and selection of soils, amendments and test sites. The actions in progress in WP2 are:
1. Use of Green Liquor Dregs (GLD) for soil improvement to construct sealing layer. Three sites in Sweden are investigated.
2. Amendment of sulphide bearing soil to mitigate the effect of oxidation.
3. Effect of water percolation on slope stability.
4. Assessment of regulatory barriers to the use of upgraded geomaterials.
5. Design and optimisation of water distribution systems to improve heap leaching.

WP3: Advanced constitutive, physical and numerical modelling

WP3 is primarily focused on developing new constitutive and numerical modelling and decision support tools that can be employed in the analysis, design and construction stages to predict the long-term behaviour of improved waste geomaterials. This WP will contribute to the development of solutions and tools to better understand and predict the behaviour of treated waste geomaterials and hence improve/enhance their use in engineering practice.

The first step of the implementation of the project was the identification and selection of soils, stabilising agents and test sites, as well as development of frameworks for the numerical and constitutive modelling tools. The actions in progress in WP3 are:

1. Self-learning finite element method (FEM) applied to field testing/monitoring and constitutive model development.
2. Modelling hydro-mechanical behaviour of upgraded waste geomaterials using data mining.
3. Experimental, constitutive and numerical modelling of fly ash stabilized soils.
4. Effects of chitosan biopolymer on stabilization of sandy soil
5. Decision support system for the management of excavated waste geomaterials.
The in situ and laboratory testing campaigns will provide data on the behaviour of different treated soils. These data will be used to study various mechanical and transfer properties of treated soils, develop material constitutive models for treated soils, develop, calibrate and apply numerical models to predict the short- and long-term behaviour of upgraded waste geomaterials. By the end of the project, it is expected that we will release a host of innovative physical, constitutive, and numerical modelling tools and techniques that can be used to better understand and predict various aspects of behaviour of treated soils at design and construction and during their service life.

Potential impacts of the project will include:

- Enhancing the potential and future career perspectives of the staff members through collaboration with leading researchers and practitioners in the GeoRes network.
- Development of new and lasting research collaborations resulting from the intersectoral and/or international secondments and the networking activities.
- Self-sustainability of the partnership after the end of the project. The detailed knowledge of the research infrastructure of each of the participating teams acquired in the course of the exchanges will help set up future joint research projects. A number of opportunities have already been identified/exploited for new joint research proposals.
- Contribution to the improvement of the research and innovation potential within Europe and worldwide.

The participants’ expertise in experimental modelling, numerical modelling, theoretical modelling, different areas of geotechnics, geoenvironmental engineering, geochemistry, mining and different fields of application (compacted soils, reuse of mine tailings, reuse of sediments/dredged soils, mass stabilisation, etc) provides a basis for new knowledge and technological development.