Durability of Fibre Reinforced Polymer (FRP) rods in low carbon concrete

Fiber-Reinforced Polymer (FRP) bars have emerged as a promising alternative to conventional steel reinforcement in the construction industry due to their superior durability performance. FRP bars exhibit non-corrosive properties, effectively addressing the primary issue of steel corrosion-induced degradation in concrete structures. Steel corrosion can lead to prohibitive repair costs in civil infrastructure and brittle catastrophic failures (e.g., the collapse of Morandi bridge). Despite the corrosion-free nature of FRP rods, their matrix/resin component plasticises when exposed to humid conditions (e.g., at a concrete crack location) and degrades due to chemical attack. This is more critical for matrix dominated properties of concrete structures reinforced with FRP bars such as the bond, shear and transverse compressive strength of FRPs. This project focuses on a comprehensive examination of the long-term performance of Glass Fiber Reinforced Polymer (GFRP) and Basalt Fiber Reinforced Polymer (BFRP) bars under various environmental conditions by simulating aggressive environmental conditions, including elevated temperatures, saline, and alkaline exposures, to evaluate the performance of GFRP and BFRP bars.

The project aims to create a test protocol that correlates FRP durability performance under accelerated ageing conditions and short-term exposures with actual on-site conditions. Key variables of interest are resin dominated properties in of FRPs and effect of stress conditions. This test protocol will shed light on the reliability of commonly applied accelerated ageing tests adopted in lab conditions. The test protocol is adopted for both resin samples and FRP bars to obtain an in-depth understanding of how the individual constituents, fiber, matrix perform but also the FRP system performs accounting also for fiber-matrix interfaces. The potential incorporation of FRP bars under applied stresses adds a crucial dimension by examining their degradation properties when subjected to load-bearing conditions while exposed to aggressive environments, closely mimicking real-world applications.

FRP bars will be examined after being exposed to normal and accelerated conditions to be tested to measure their interlaminar and transverse shear strength. Non-exposed and pre-exposed FRP bars will be cast in concrete beams and blocks to measure the effect of exposure degradation on the bond and flexural performance of FRP bars in concrete structures. Resin samples will be cast, exposed, and tested separately to see the effect of direct exposure to pure resin samples after being tested in tension and shear. The type of exposure that will be used to understand the acceleration effect of the used protocol will be by comparing the degradation effect of directly exposed FRP samples in an alkaline mixture that replicates the pH and chemistry of concrete but at elevated temperatures to increase the diffusion to the composite material.

The outcomes of this project offer wide-ranging benefits to the construction industry and sustainability endeavors:

a. Enhanced Infrastructure Durability: The development of FRP bars with improved long-term performance can extend the lifespan of concrete structures, resulting in reduced maintenance costs and enhanced sustainability.

b. Advancing Net-Zero Construction: The utilization of low carbon concrete reinforced with FRP bars aligns seamlessly with the UK's net-zero emissions targets, making this research directly relevant to sustainability goals.

c. Industry-Wide Adoption: The newly established acceleration protocol can be readily adopted across the construction industry to assess the durability of FRP bars, ensuring the reliability and safety of construction projects.

This project delves into the promising realm of Fiber-Reinforced Polymer (FRP) bars as a durable alternative to traditional steel reinforcement in construction while working towards more sustainable and durable approaches.

There are seven principal groups of beneficiaries for our new EPSRC Centre for Doctoral Training in Composites Science, Engineering, and Manufacturing.

1. Collaborating companies and organisations, who will gain privileged access to the unique concentration of research training and skills available within the CDT, through active participation in doctoral research projects. In the Centre we will explore innovative ideas, in conjunction with industrial partners, international partners, and other associated groups (CLF, Catapults). Showcase events, such as our annual conference, will offer opportunities to a much broader spectrum of potentially collaborating companies and other organisations. The supporting companies will benefit from cross-sector learning opportunities and

- specific innovations within their sponsored project that make a significant impact on the company;
- increased collaboration with academia;
- the development of blue-skies and long-term research at a lowered risk.

2. Early-stage investors, who will gain access to commercial opportunities that have been validated through proof-of-concept, through our NCC-led technology pull-through programme.

3. Academics within Bristol, across a diverse range of disciplines, and at other universities associated with Bristol through the Manufacturing Hub, will benefit from collaborative research and exploitation opportunities in our CDT. International visits made possible by the Centre will undoubtedly lead to a wider spectrum of research training and exploitation collaborations.

4. Research students will establish their reputations as part of the CDT. Training and experiences within the Centre will increase their awareness of wider and contextually important issues, such as IP identification, commercialisation opportunities, and engagement with the public.

5. Students at the partner universities (SFI - Limerick) and other institutions, who will benefit from the collaborative training environment through the technologically relevant feedback from commercial stakeholder organisations.

6. The University of Bristol will enhance their international profile in composites. In addition to the immediate gains such as high quality academic publications and conference presentations during the course of the Centre, the University gains from the collaboration with industry that will continue long after the participants graduate. This is shown by the

a) Follow-on research activities in related areas.
b) Willingness of past graduates to:

i) Act as advocates for the CDT through our alumni association;
ii) Participate in the Advisory Board of our proposed CDT;
iii) Act as mentors to current doctoral students.

7. Citizens of the UK. We have identified key fields in composites science, engineering and manufacturing technology which are of current strategic importance to the country and will demonstrate the route by which these fields will impact our lives. Our current CDTs have shown considerable impact on industry (e.g. Rolls Royce). Our proposed centre will continue to give this benefit. We have built activities into the CDT programme to develop wider competences of the students in:

a) Communication - presentations, videos, journal paper, workshops;
b) Exploitation - business plans and exploitation routes for research;
c) Public Understanding - science ambassador, schools events, website.