The tuff powder with different specific surface areas(SSA)was used to replace 30%cement(calculated by the total mass of cementitious materials),and the effect of the tuff powder with different SSA on the paste flowability,mortar strength and cement hydration heat was studied.The effect of replacing cement with tuff powder on carbon emissions was analyzed.The results show that when replacing cement with the 381 m2/kg SSA tuff powder,the paste initial flowability is improved,but as the SSA of tuff powder is increased,the initial flowability of paste is significantly decreased.The contribution of tuff powder with different SSA to the 3 d compressive strength of mortar is similar to that of fly ash and ground granulated blast furnace slag,but its contribution to the 28 d and 56 d compressive strength of mortar is lower than that of fly ash and ground granulated blast furnace slag.The increasing of the SSA of tuff powder is beneficial for improving the compressive strength of mortar,but the effect of improving strength is limited when the SSA of tuff powder is increased from 495 m2/kg to 700 m2/kg.Taking into account both economic and compressive strength of mortar,the tuff powder is suitable to grind to 495 m2/kg SSA when it is used as a mineral admixture.The fly ash,ground granulated blast furnace slag and tuff powder all reduce the peak of hydration heat rate and 72 h cumulative heat of cement.The acceleration of tuff powder with the SSA of 700 m2/kg for cement hydration is higher than that of fly ash,ground granulated blast furnace slag and other tuff powder.The composite cementitious material made by replacing 30%cement with 495 m2/kg SSA tuff powder,reduces carbon emissions by 29.5%compared to 100%cement.
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