Structural behavior of reinforced low-carbon concrete beams adapted for precast

Abstract

This study evaluates the structural behavior of two low-carbon self-compacting concretes in comparison to an Ordinary Portland Cement (OPC) concrete, used as a reference: a binary binder S70 (OPC substituted by 70% of ground granulated blast furnace slag, GGBS,−58% of carbon emission (em-CO₂) versus OPC) and a supersulfated cement SSC (− 78% of em-CO₂ versus OPC).

For each binder, a mechanical characterization through compressive strength, tensile strength and Young’s modulus tests after 28 days and 90 days, was carried out. Steel–concrete bonding at 28 days was also tested through pull-out tests. Additionally, two beams per binder (3-meter long, section 280 × 150 mm²) were cast, varying the longitudinal reinforcement section: a low steel reinforcement ratio (1.6 cm², Conf1) leading to steels rupture, and a high steel reinforcement ratio (7.1 cm², Conf2) for higher beam resistance. The design of the beams was made according to Eurocode 2. Beams were tested using 4-point bending test with the recording of strains at different locations of the beam using Digital Image Correlation (DIC).

For both configurations, S70 and SSC binders resulted in an equivalent load–deflection behavior compared to OPC beam, despite lower mechanical properties for SSC concrete, while reducing the associated carbon emissions. The DIC system helped to explain the observed fracture modes (reinforcements or “shear force” ruptures) and revealed slight differences in behavior between the beams, such as variations in the position of the neutral axis, as well as number of cracks and opening. These results suggest that structures with low-carbon binders can be dimensioned according to Eurocode 2, similar to OPC.