Low Carbon Concrete: Fair and Rapid Assessment of Slowly Reacting Cement Concrete

Responding and reducing the climate emergency concrete construction must play a significant role worldwide. The main of most carbon-limiting technologies is to reduce the Portland clinker content to increasingly high levels, typically with secondary cementitious materials such as fly ash. While it may be possible to design such mixes for a particular strength there are implications for durability. Durability tests are carried out at the standard age of 28 days, however, fly ash is a slowly reacting cement and do not reach ‘maturity’ until at least 90 days. Testing them at 28 days if, therefor, unreliable and risks unfairly defining their durability performance.

In this paper the authors will demonstrate an elevated temperature cycle that can achieve equal ‘maturity’ to 90 day standard curing to 21 days to provide an industrially relevant and practical test methodology. The paper will also show that as well as equal strength the microstructure and pore fluid chemistry is broadly similar. Data from durability tests for carbonation and chloride ingress are provided, which also show the applicability of the proposed test method.

Fairly Assessing Slowing Reacting Cement for Low Carbon Concrete Authors Prof. Rod Jones - United Kingdom - University of Dundee Abstract Responding and reducing the climate emergency concrete construction must play a significant role worldwide. The main of most carbon-limiting technologies is to reduce the Portland clinker content to increasingly high levels, typically with secondary cementitious materials such as fly ash. While it may be possible to design such mixes for a particular strength there are implications for durability. Durability tests are carried out at the standard age of 28 days, however, fly ash is a slowly reacting cement and do not reach ‘maturity’ until at least 90 days. Testing them at 28 days if, therefor, unreliable and risks unfairly defining their durability performance. In this paper the authors will demonstrate an elevated temperature cycle that can achieve equal ‘maturity’ to 90 day standard curing to 21 days to provide an industrially relevant and practical test methodology. The paper will also show that as well as equal strength the microstructure and pore fluid chemistry is broadly similar. Data from durability tests for carbonation and chloride ingress are provided, which also show the applicability of the proposed test method.