Potential of Gluconic Acid as Retarding Admixture in Concrete

The increasing demand for ready-mix concrete (RMC) due to rapid urbanization and infrastructure development has necessitated the use of efficient admixtures to enhance workability and control setting time. This study investigates gluconic acid (GA), a weak organic acid derived from glucose, as a sustainable retarding admixture in concrete. GA was incorporated at dosages ranging from 0.02% to 0.1% by weight of cement. Its effects on setting time, workability retention, compressive strength, and durability were systematically evaluated. Results showed that GA significantly prolonged the initial setting time up to 170 minutes and the final setting time up to 550 minutes. At a dosage of 0.1%, workability was maintained with a slump above 150 mm for up to 180 minutes. Furthermore, compressive strength increased by 10.8% at 3 days and 6% at 28 days, compared to the control mix. Durability, assessed using the Rapid Chloride Permeability Test (RCPT), indicated extremely low chloride ion penetration across all mixes. These findings demonstrate that GA is an effective and eco-friendly alternative to conventional retarders in concrete applications, offering both early strength enhancement and extended workability.