Transport characteristics of concrete after carbonation

ABSTRACT

Limited information is available on the transport behaviour of concrete after being exposed to carbon dioxide, which is one of the major reasons for the premature deterioration of reinforced concrete structures. This study investigates the changes induced in the transport characteristics of concrete after carbonation through conventional tests on concrete such as porosity, sorptivity, oxygen permeability and resistivity. A total of 10 concrete mixes were prepared using five supplementary cementitious materials (SCMs) (Class C fly ash, Class F fly ash, pumice, perlite and calcined clay) at the 30% cement replacement level and two water to binder ratios. The concrete samples were cured for 28 days in water and were subsequently placed under three different exposure conditions (2.5% CO₂, oven 50°C and under water) for 60 days. In general, a reduction in porosity was observed on carbonation in all the concrete mixes. However, for SCM-incorporated concrete mixes, an inferior sorptivity, permeability and resistivity performance were observed specifically for lower compressive strength concrete mixes and clay mixes.

KEYWORDS:

• Carbonation
• porosity
• resistivity
• permeability
• shrinkage

Acknowledgments

The authors would like to acknowledge the financial support provided by BRANZ and Concrete NZ for this project.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This work was supported by the Building Research Association of New Zealand.

Notes on contributors

Vineet Shah

Vineet Shah is a senior research scientist at Callaghan Innovation, New Zealand. His research interests include low carbon binders, cement chemistry and concrete microstructure and durability of concrete structures.

James Mackechnie

James Mackechnie is an education, training and research manager at Concrete NZ. James has over 25 years of industrial and academic experience specifically in the area of concrete durability, fresh properties of concrete and policy guidelines.