The ability of sodium metasilicate pentahydrate to adjust the compatibility between synthetic Fluid Loss Additives and Retarders applying in oil well cement

Schematic of sodium metasilicate pentahydrate adjusting the compatibility between synthetic Fluid Loss Additives and Retarders. [Display omitted] •The increase of adsorption sites of cement hydration products is the key factor to SMP adjustment the compatibility between the admixtures.•Through the modification of pore size distribution of cement hydrated particles, SMP could effectively alleviate the super-retardation of cement slurry caused by the carboxyl group in the admixtures.•The effects of SMP on the compatibility and the early strength of cement are achieved by promote the formation and growth of early cement hydration products. Sodium metasilicate pentahydrate (SMP), a type of hardening-accelerator, was widely used in cement slurry to enhance its early strength. In this study, we found that SMP had an novel ability to adjust the compatibility between 2-Acrylamido-2-Methyl Propane Sulfonic Acid (AMPS)-based Fluid Loss Additive (FLA) and Retarder in oil well cement. Reasons for this significance were proposed, that SMP promoted the formation and growth of hydration products by accelerating the hydration velocity of cement slurry, which increased the adsorption sites of cement hydration products. As that happens, the more AMPS-based polymers were adsorbed simultaneously on the surface of the hydration product, thereby effectively improving the compatibility problem caused by the competitive adsorption between the admixtures. Meanwhile, while SMP speeded up the hydration reaction, the pores space of cement hydrated particles were filled with more hydrates and consequently altered its pore size distribution, whose action was also beneficial to the development of early strength. Overall, those findings will provide further interpretation for the effect of admixture on cement hydration products and offer some useful references for practical application of oil well cementing in the future.