关键词: 碱式硫酸镁水泥;碱萃取物;凝结时间;流动度;强度;水化产物

Abstract: The influence of straw fiber alkaline extractives on setting time, fluidity and strength of basic magnesium sulfate cement were studied.The phase composition of hydration products in harden cement were tested by XRD.The results show that water-solubles present in straw fiber decrease the fluidity and retard the setting time of cement, and the strength of cement in early period is reduced.The extracts present in straw fiber have an adverse effect on MgO hydration and the formation of[Mg(OH) (H2O)x]+formed.Therefore,the growth of 5Mg(OH)2· MgSO4· 7H2O(5· 1· 7)phase is inhibited and the development of the cement strength in early stage is slow.Comparing with the basic magnesium sulfate cement mixed with H2O,the NaOH solution accelerate the setting time, interfere the normal fluidity and strength development process of the cement.The content of Mg2+is reduced due to the forming of Mg(OH)2after the reaction between NaOH and MgSO 4, leading to the reduction of cement strength.

Key words: basic magnesium sulfate cement;alkaline extractive;setting time;fluidity;strength;hydration product