Carbon nanotube effects on low-cement mortar performance and eco-efficiency

The construction sector, particularly cement production, accounts for 8-10 % of global CO2 emissions annually, and the industry is under increasing pressure to adopt sustainable practices, with carbon nanotubes (CNTs) emerging as a promising solution to improve cement-based composites while reducing cement use and CO2 emissions. This study evaluates the feasibility of compensating for reducing clinker content in a mortar using CNTs in isolation, without additional fillers or additives. The research focuses on evaluating CNT dispersion techniques, assessing different CNT contents and water-tocement (w/c) ratios, analyzing the impact of CNTs in low-cement mortars, and evaluating the eco-efficiency of the mortars with or without CNTs and cement reduction. The experimental program involved determining the best CNT dispersion technique for a fixed 0.05 % CNT (by mass of cement, mc) content. Next, CNT contents (up to 0.2 % mc) and w/c ratios (0.5 and 0.6) were evaluated for their influence on compressive strength, flexural strength, porosity, and water absorption at 28 days. Finally, the study assessed the effects of adding CNTs to reduced-cement mortars with up to 10 % cement reduction. Among the main conclusions, mixing CNTs with water and manual agitation was the best dispersion technique. Besides, incorporating 0.05 % CNT improved mechanical and physical properties, while higher contents (above 0.10 % mc) led to performance declines. Lastly, adding 0.05 % CNT compensated for strength losses in reduced-cement mortars and improved eco-efficiency, suggesting that CNTs offer both environmental and technical advantages