The Durability of Rebar in Low-Carbon Concrete: Natural Pozzolan and Rice Husk Ash

Ordinary Portland cement has a high carbon footprint, and environmental concerns necessitate the use of Supplementary Cementitious Materials (SCMs) such as natural pozzolan and slag to reduce embodied carbon while maintaining structural performance and durability. However, the influence of low-carbon binders on the bond behaviour and durability of reinforced concrete remains insufficiently understood, particularly due to changes in pore solution alkalinity. This PhD research aims to investigate the impact of low-carbon binders on bond behaviour and long-term durability, with a focus on steel passivation and interfacial properties. Natural pozzolan and Rice Husk Ash (RHA) will be the key SCMs to be investigated with slag being the reference SCM. RHA is highlighted as a sustainable cementitious addition due to its potential for waste valorisation. Despite their lower global warming potential, these SCMs reduce alkalinity of concrete and may compromise the passive protection of steel in concrete leading to accelerated corrosion of the embedded steel in reinforced concrete. The research focus is on the interfacial behaviour of rebar in low-carbon concrete. Fibre-reinforced polymer bars are employed as an eco-friendly corrosion resistant benchmark to evaluate the degradation of steel reinforcement arising from the loss of passive protection in low-carbon concrete. A pull-out test methodology is adopted as the primary performance indicator to enable the assessment of bond strength and its performance over time. Chlorides are introduced in the concrete to accelerate aggressive environmental conditions. The pull-out response will be used as a durability index and to validate finite element models. The findings will contribute to the development of performance-based design approaches and support the adoption of bio-based and geo-based materials in accordance with global sustainable development goals.