Lower-carbon concretes have cement-based binders partially substituted with supplementary cementitious materials (SCMs), which reduce embodied carbon. However, this substitution also increases susceptibility to carbonation and potentially for carbonation-induced corrosion. The transport properties of the binder play a crucial role in understanding these risks. Understanding these properties is already complex in plain cement systems, and the challenge is further amplified when cement is partially replaced with SCMs. This study uses neutron radiography to investigate water transport properties in low-carbon cementitious materials by capillary action. The technique allows for visualization of the changes in the water content, enabling estimation of the water transport rate through cement paste and SCM-blended binders. The findings show marked differences in water transport rates between pastes and mortars with and without SCMs, as well as between carbonated and non-carbonated samples. Considering that corrosion propagation in carbonated concrete depends on its transport properties, these observations provide insights into the potential durability characteristics.