Understanding the role of polyepoxysuccinic acid in one-part sodium carbonate and carbide slag activated ground granulated blast furnace slag fresh paste

In this study, polyepoxysuccinic acid salt (PESA (Na), P) was employed to enhance the time-dependent flowability of the one-part sodium carbonate and carbide slag activated ground granulated blast furnace slag paste within 60 min. The action mechanism of P with different addition methods was revealed through pore solution chemistry, in-situ XRD, Zeta potential, etc. For the direct addition method, P (0.2 wt% to 0.3 wt%) could adsorb onto the ground granulated blast furnace slag (GBS) and carbide slag (CS), offering dispersibility and inhibiting the dissolution of carbide slag, thereby improving the initial flowability. Then, P lost its dispersible capability because it participated in the formation of calcite and gaylussite, inhibiting the growth of calcite along the (104) crystal plane and leading to the fast consumption of CO₃^2- in the pore solution. 0.4 wt% P retained high CO₃^2- while low OH^- during the test period, delaying the chemical reaction between CS and sodium carbonate. For the delayed addition method, 0.1 wt%-0.3 wt% P significantly improved the flowability of the paste under high OH^- concentrations within 60 min. In this case, calcite was allowed to precipitate in advance so that P was not consumed by calcite and gaylussite but adsorbed onto chemically inert calcite, GBS, and unreacted CS to provide strong dispersibility. Both addition methods promoted the formation of gaylussite with large molar volumes and a rough appearance, which was detrimental to the flowability. A modelled chemical system comprising "Na₂CO₃+Ca(OH)₂" with and without P validated the investigated mechanisms.