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To address present concerns about thickening time and high early-strength in deepwater cementing at low temperatures when using conventional accelerators,a new type of set-accelerating admixture comprising of lithium chloride,aluminium hydroxide and alkaline metal chlorides,named as LS-A,was studied in this paper.Mechanism analysis and performance tests show that the accelerator LS-A accelerated the hydration of tri-and dicalcium silicates (C 3 S and C 2 S) at low-temperatures by speeding up the breakdown of the protective hydration film and shortening the hydration induction period.Therefore,LS-A could shorten the low-temperature thickening time and the transition time of critical gel strength from 48 to 240 Pa of the Class-G cement slurry,and improve the early compressive strength of set cement at low-temperatures.It exhibited better performance than calcium chloride and had no effect on the type of hydration products,which remain the same as those of neat Class-G cement,i.e.the calcium silicate gel,Ca(OH) 2 crystals and a small amount of ettringite AFt crystals.LS-A provides an effective way to guarantee the safety of cementing operations,and to solve the problems of low temperature and shallow water/gas flowing faced in deepwater cementing.
To address the recent concerns about thickening time and high early-strength in deepwater cementing at low temperatures when using conventional accelerators, a new type of set-accelerating admixture comprising lithium chloride, aluminum hydroxide and alkaline metal chlorides, named as LS-A, was studied in this paper. Mechanism analysis and performance tests show that the accelerator LS-A accelerated the hydration of tri-and dicalcium silicates (C 3 S and C 2 S) at low-temperatures by speeding up the breakdown of the protective hydration film and shortening the hydration induction period.Therefore, LS-A could shorten the low-temperature thickening time and the transition time of critical gel strength from 48 to 240 Pa of the Class-G cement slurry, and improve the early compressive strength of set cement at lt- meter.It attracts better performance than calcium chloride and had no effect on the type of hydration products, which remain the same as those of neat Class-G cement, iethe calc ium silicate gel, Ca (OH) 2 crystals and a small amount of ettringite AFt crystals. LS-A provides an effective way to guarantee the safety of cementing operations, and to solve the problems of low temperature and shallow water / gas flowing faced in deepwater cementing.