# Influence of crack width on carbonation depths in functionally layered concrete

## TL;DR

This paper studies how cracks in layered concrete affect carbonation, showing that cracks allow faster carbonation in the inner concrete.

## Contribution

The study reveals how crack width and durability layer thickness influence carbonation progression in functionally graded concrete.

## Key findings

- Cracks allow carbonation to penetrate into the interior concrete mix.
- Durability layer thickness reduces carbonation in areas away from cracks.
- Full steel encasement in the durability layer limits carbonation influence zones.

## Abstract

In functionally graded concrete, an outer durable concrete layer with higher cement can be used to protect lower grade interior concrete to maintain durability performance while reducing embodied carbon. However, flexural cracks in reinforced functionally layered beams can penetrate through the durability layer into interior concrete. Accelerated carbonation behaviour of cracked beams with different durability layer thicknesses and crack widths was investigated. Digital tools were used to trace the carbonation profiles. In regions remote from cracks the durability layer reduced carbonation ingress. At a crack, the carbonation front in the layered beams progressed into the interior mix. The width of the carbonation influence zone around the reinforcement was smaller when the steel was fully encased in the durability layer.