Sodium tetraborate is used as a retarder to investigate its role in regulating the setting time of AAS,and combined with the heat of hydration,micro-morphology,physical phase composition,chemical bonding,and pore structure analysis to explain the microstructural evolution of the behaviour of the retardation mechanism is revealed.The results show that when the dosage of sodium tetraborate is 0～20％(in terms of slag mass),the initial setting time of AAS is ex-tended from 19 min to 377 min,the final setting time is extended from 26.5 min to 455 min,and the loss rate of 56 d com-pressive strength can be controlled within 19％.Sodium tetraborate makes the C-A-S-H gel's diffraction peak of AAS shift to a large angle,the hydration induction period is prolonged,the number of gel pores(＜10 nm)and capillary pores(10～100 nm)increases,and the pore structure is coarsened.The mechanism of retardation is:sodium tetraborate forms a boron complex coating layer on the slag surface,hindering the migration of ions involved in the reaction and delaying the hydration reaction.
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