Influence of crack width on carbonation depths in functionally layered concrete

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.