GRP Rebar: A Technical Guide

The design, specification and use of glass-fibre reinforced polymer reinforcing bar in the UK market.

GRP reinforcing bar has been used in concrete for more than forty years, is covered by mature design guidance in North America, Japan and Canada, and now sits within Eurocode 2 through Annex R of BS EN 1992-1-1:2023. Yet many UK engineers have never specified it and many contractors have never handled it, and the same questions come up on almost every project: how strong is it, how do I design with it, what standard do I quote, can it be bent on site and how long will it last.

Written by Gavin Williams, Managing Director of Engineered Composites Ltd, the UK’s only manufacturer of GFRP reinforcing bar, this guide answers those questions candidly. It is clear about where GRP rebar is the better choice, where chloride attack, electromagnetic interference, machinability or whole-life cost drive the decision, and equally clear about where steel remains the right answer.

The guide is structured in four parts, mirroring the format of the author’s earlier book on GRP pultruded profiles.

Part I covers the fundamentals: what GRP rebar is, how it is manufactured, its material properties and its durability, including independent accelerated ageing test data on Engineered Composites bar from Hohai University.

Part II maps the standards landscape onto the UK market, from ASTM D7957 and CSA S807 through to ACI 440.1R-15, ACI CODE-440.11-22 and Eurocode 2 Annex R, and shows exactly what to write in a specification.

Part III sets out the engineering design principles for flexure, serviceability, creep rupture, shear, anchorage and fire, with a fully worked example of an externally exposed slab and detailing rules covering cover, bends, BS 8666 shape codes and hybrid GRP and steel reinforcement.

Part IV covers applications and case studies across sea defences, marine structures, tunnelling soft-eyes, rail, MRI suites, utilities, bridges and precast, alongside installation and site practice, whole-life cost and sustainability, frequently asked questions and future developments.

Appendices provide the Engineered Composites rebar product specification, the full Hohai University durability report, shape codes, a comparison with alternative reinforcement, standards and references, a glossary, a model specification clause and a design checklist.

This book is written for practising structural engineers who want to understand how the design rules differ from steel, for specifiers who need the right clause and the right test certificate, for contractors who need to know how to handle, cut and fix GRP bar on site, and for clients and asset owners weighing up corrosion-free reinforcement on marine, rail and infrastructure projects.

Design equations are summarised from the published standards cited, and product data reflects the current Engineered Composites product specification and independent test reports. The result is a practical reference that brings GRP rebar inside the framework UK engineers and approving authorities already use.

This guide is intended to supplement, not replace, the expertise of qualified structural engineers. All structural designs must be carried out by suitably qualified professionals in accordance with applicable codes, standards and regulations.

First Edition, 2026. Written by Gavin Williams, Managing Director, Engineered Composites Ltd, Chester, United Kingdom.