Development and field validation of pumpable alkali-activated ground granulated blast furnace slag binder-based concrete using sodium gluconate as a retarder

In this study alkali-activated concrete mixtures with a high calcium-based precursor and with prolonged workable times were developed and its site application for pumping activity was validated through a field study. This was achieved by formulating mixtures with pumpable workability and extended workable times. Sodium gluconate was used as a retarder to extend the workable time. The influence of sodium gluconate on the fresh properties of alkali-activated paste mixtures, such as setting time, spread diameter retention, yield stress, apparent viscosity and the evolution of storage modulus, was investigated. The effect of sodium gluconate on the pore solution composition and its pH and the amount and type of hydration products in alkali-activated systems were also studied using inductively coupled plasma atomic emission spectroscopy (ICP-AES), thermogravimetric analysis (TGA) and Fourier transform infrared spectroscopy (FTIR). Zeta potential measurements were also performed to understand the adsorption of sodium gluconate and its impact on the surface charge of GGBFS particles. The studies on paste revealed that sodium gluconate is an effective retarder that prolongs the setting and workable times. Zeta potential and rheological studies illustrated the dispersive property of sodium gluconate. The experiments were also performed on concrete systems to understand the slump retention and compressive strength. Concrete mixtures with compressive strength in the range of 38–46 MPa at 28 days and a spread diameter above 350 mm retained at 150 min were obtained. Further, the developed concrete mixture was evaluated for pumpability by pumping the concrete through a pipe conduit after a long-haul time of 180 min. The effective pumping of the formulated alkali-activated concrete mixes shall facilitate the practical use of alkali-activated materials in construction projects. The durability performance of the developed pumpable alkali-activated GGBFS concrete mixture was also evaluated by measuring the carbonation depth, the chloride migration coefficient and performing rapid chloride penetration test on the extracted core samples after exposure to natural weathering for 510 days. © 2024 Elsevier Ltd