Effects of Sugar Cane Bagasse Ash on the Properties and Hydration of Magnesium Potassium Phosphate Cement
Sugar cane bagasse ash(SCBA)is a waste produced in the process of sucrose production.Because SCBA is rich in yield and has pozzola-nic activity,it has been gradually used for building materials.In this work,the effects of SCBA with different content and particle size on the setting time,fluidity,compressive strength,volume stability,mass loss,hydration process and products and microstructure of magnesium potas-sium phosphate cement(MKPC)were studied.The results showed that the dilution effect of SCBA slowed down the increase of pH of MKPC,which can delay the early hydration and increase the setting time and early strength(before 24 hours)of MKPC.However,with the increase of pH value in the middle and later stages,SCBA played a filling role and nucleating effect.The amount of hydration products of MKPC increased,and some new amorphous aluminum phosphate,potassium silicate,and calcium gelled hydration products were formed.It can result in a denser structure and higher strength in the medium and long term.Because the hydration rate of early MKPC gradually decreased with the increase of SCBA content,the formation of early hydration product K-struvite decreased,and the early shrinkage decreased.The proportion of connected pores with the size of 50-100 nm and less than 50 nm increased in the middle and late stage,which accelerated the evaporation and migration of free water,and increased the mass loss and drying shrinkage.When the content of SCBA with small particle size is 20％,the comprehensive performance of MKPC is better.This study can provide a theoretical basis for SCBA as a substitute for MKPC cementitious material,and further promote the application of agricultural by-products in new cementitious materials.
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