Valorisation of wind turbine blades into concrete : a contribution towards a more sustainable approach

The development of wind energy in the last decades led to the massive construction of wind turbines throughout the world. With 20 years of project service life, today older turbines are at the end of their service lifecycle. While the large part of wind turbine is recyclable, no valorisation of solution exists now for its blades. With a predicted growth of wind energy around the world, the necessity of finding proper valorisation of solutions becomes critical. On the other hand, concrete is one of the most popular building materials with a major negative environmental impact. The valorisation of wind turbine blades in concrete could be the solution that bears a high potential not only to decrease the environmental impact of landfilling old wind turbine blades, but also to reduce the environmental impact of concrete production by partial replacement of virgin raw materials. Therefore, this thesis is aimed at investigating possible avenues for valorisation of decommissioned wind-turbine blades (DWTB) glass fiber-reinforced polymer (GFRP) materials - termed throughout this thesis as DWTB-GFRP. To this end, three distinct experimental phases have been carefully designed. The first phase includes an extensive material characterization and investigation of the influence of DWTB-GFRP on mortar performance. In the second phase, concrete mixtures were designed and tested to investigate the effects of DWTB-GFRP addition as powder, fibers and aggregates. In the third phase, selected concrete mixtures were used for plain concrete specimens and Concrete Filled Fiber Reinforced Polymer Tubes (CFFTs)-confined specimens. All specimens were tested at 28 days and 90 days after being cured in a fog room, and after being exposed to 200 freeze-thaw cycles with core specimen temperature variation between −18oC and 4oC. An analytical modeling was performed for the CFFT specimens introducing the model suitable for concretes incorporating DWTB-GFRP aggregates. The material characterization included the analysis of such important parameters of DWTB-GFRP as the chemical content, composition, mineralogy, physical characteristics, and chemical reactivity, followed by the formulation of different concrete mixtures for further testing. For the second stage, cement replacement rates of 10-30% were attempted for concrete mixtures. Coarse aggregate replacement levels of 33-100% were considered, while fiber addition rates of 1-1.75 vol. % were investigated. The resulting concretes were characterized for their compressive strength and flexural capacity. Results show that the form of DWTB-GFRP (as a powder, aggregate, or fiber) significantly impacts the properties of resulting concretes. Thus, while DWTB-GFRP powder leads to a substantial increase in the setting time (owing to the wooden content and its associated soluble sugars) as well as to a significant drop in compressive and flexural strengths, it should be noted that mixtures with 10% cement replacement by DWTB-GFRP powder (after removal of wooden content) demonstrated comparable compressive strength as that of the reference mixture (without DWTB-GFRP) at 90 days. When DWTB-GFRP is incorporated in concrete as a fiber reinforcement, an enhancement in flexural capacity of up to 15% was achieved without noticeable drop in compressive strength. For the third stage, mixtures with cement replacement rates of 10% and 20% were attempted. Coarse aggregate replacement levels of 50 and 100% were considered, while fiber addition rates of 1-1.75 vol. % were investigated. Two types of DWTB-GFRP were used: containing wood and after wood removal. Mixtures with cement and aggregate replacement were used in CFFT structures and tested after being cured in standard conditions for 28 and 90 days and exposed to 200 freeze-thaw cycles. For the mixtures with fibers addition, compressive and flexural strength, and flexural toughness of concrete cured in standard conditions for 28 and 90 days and exposed to 200 freeze-thaw cycles were investigated. The addition of DWTB-GFRP as aggregates resulted in a significant decrease in compressive strength and density of concrete with values close to the lightweight concrete compressive strength and density. The strength decrease is attributed to the low compressive strength of DWTB-GFRP aggregate and lack of bonding in the interfacial transition zone. The addition of DWTB-GFRP as powder resulted in a significant strength decrease at 28 days (due to the retardant properties of wood and the pozzolanic reaction occurring at the later ages), followed by the increase in compressive strength after 90 days (reaching between 87% and 96% of reference mix strength). The use of CFFT technology resulted in a 90-100% increase in compressive strength for all mixtures. The specimens with DWTB-GFRP aggregate addition in CFFT structure exhibited a 14-28% increase in the elastic peak strength. The CFFT filled with concrete incorporating the DWTB-GFRP powder reached compressive strengths superiors to 80 MPa after 90-day curing. The freeze-thaw exposure resulted in a decrease in the compressive strength of all specimens. Strength decrease for mixtures including wood was larger than for those with wood removed, due to the high-water absorption of wooden content increasing the freeze-thaw damage to the concrete. The strength decrease in specimens with DWTB-GFRP powder addition after freeze-thaw exposure is partly due to the wooden content with high water absorption, and partly due to the fineness influencing the pore structure. For the mixtures with fibers addition, a slight decrease in compressive strength was observed with the increase of fiber content up to 8% for 1.75% fiber with wood added. Flexural strength increased with the increase of fiber content up to 22% for 1.75% fiber without wood. A noticeable increase in flexural toughness with the increase in fiber content is observed up to 5 times for mixture with 1.75% fibers addition. The decrease of flexural strength due to the freeze-thaw exposure was more pronounced for the mixtures containing wood and was similar for normal concrete and mixtures without wood. Analytical investigation was done using the ACI 440.2R-17 model for predicting the compressive response of confined concrete incorporating DWTB-GFRP lightweight aggregates, demonstrating the inaccuracy of the existing model for the DWTB-GFRP aggregates. A modified model more sensitive to GFRP aggregates and with higher predictive ability was proposed using the correcting coefficients as a function of the aggregate replacement level. These coefficients were incorporated into the ACI 440.2R-17 equations demonstrating the ability to predict more accurately the behavior of CFFT specimens with DWTB-GFRP aggregates while being accurate for the Reference concrete (with 0% addition level). In general, the research project supports decommissioned wind turbine blade material valorisation of in concrete as a prospective solution. The DWTB-GFRP can be used as a lightweight aggregate, pozzolan, and an effective fiber reinforcement in concrete. The use of concrete-filled fiber reinforced polymer tube application allows the creation of concrete structures with high compressive strength and density of lightweight concrete (for DWTB-GFRP aggregates) and greener concrete of superior compressive strength (for DWTB-GFRP powder).

Name thesis:degree_name

Ph. D.

Level thesis:degree_level

Doctorat

Discipline thesis:degree_discipline

Génie civil

Grantor dc:publisher

Université de Sherbrooke

Year dc:date.issued

2022

Author dc:creator

• Baturkin, Dmitry

Advisors dc:contributor.advisor

• Masmoudi, Radhouane
• Tagnit-Hamou, Arezki

• Wind turbine blade waste materials
• Concrete-filled fibre-reinforced polymer tubes
• Glass fiber-reinforced polymer
• Recycled materials
• Concrete

Language dc:language.iso

fr, en

Handle dc:identifier.uri

http://hdl.handle.net/11143/19924

OAI identifier oai:identifier

oai:usherbrooke.scholaris.ca:11143/19924