Optimal mixture design method for low-CO2 limestone-calcined clay cement (LC³) concrete considering climate change and carbonation durability: A case study of eight countries

초록

Limestone-calcined clay cement (LC3) concrete offers significant carbon reduction potential, but current mix design practices neglect carbonation durability and climate change impacts, risking reinforcement corrosion. This study proposes a mixture design method for low-CO2 LC3 concrete that explicitly incorporates carbonation durability and CO2 concentration changes. Eight cities from various countries (New Delhi, Bern, Beijing, Havana, Dhaka, Bras & iacute;lia, Pretoria, and Hanoi) were selected on the basis of their resource suitability, emission needs, and LC3 development activities and analyzed under three design scenarios: (1) without carbonation durability, (2) with 0.04 % CO2, and (3) with 0.05 % CO2. The strength constraint required a 28-day compressive strength >= 30 MPa, and the carbonation durability limited the 50-year carbonation depth to <= 25 mm. A genetic algorithm generated optimal mix designs for each city and scenario. In Scenario 1, the mix compositions were identical across cities, but the carbonation depths varied. New Delhi, Beijing, and Pretoria exceeded the 25 mm limit due to moderate humidity. Other cities with higher humidities met the durability requirements. In Scenario 2, the mix designs in New Delhi, Beijing, and Pretoria increased the binder content to improve durability; other cities remained unchanged. In Scenario 3, a higher CO2 led to similar to 11.8 % carbonation depth increases in some cities, but only Bras & iacute;lia's design dominance shifted from strength to durability, indicating the potential impact of climate change on future design. Across all the scenarios, calcined clay and limestone achieved maximum substitution because of their dual benefits in terms of strength contribution and low emissions. The results showed that lower water-to-binder ratios increased both compressive strength and emissions, validating the method's consistency with engineering practices.

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