Influence Of The Fineness Of Cement On Its Hydration Process And Properties

The fineness of cement has a significant influence on its mechanical properties,workability,durability and other properties,and also affects the cost and energy consumption of cement production.With the development of cement production,the fineness of cement increases constantly,and the understanding and requirements of cement fineness are also changing again and again.Exploring the influence of cement fineness on the properties of cementitious materials can provide a certain reference for cement production and application.In this paper,the influence of cement fineness on its hydration process and mechanical properties was studied under different curing conditions at room temperature and high temperature,as well as the interaction with mineral admixtures.The main work contents and conclusions were as follows:(1)The influence of cement fineness on its hydration process and mechanical properties under room temperature curing condition was studied.The results show that the higher the fineness of cement is,the higher the early strength is,but the subsequent strength increases slightly,and the strength of fine cement will be exceeded by coarse cement in the long age.The stagnation or reduction of mortar strength may be related to the change of pore structure of cement paste.The higher the fineness of cement,the higher the hydration rate and degree of hydration in early age,but the later hydration rate is low,the subsequent increase of hydration degree is slight.(2)The influence of cement fineness on its hydration process and mechanical properties under high temperature curing condition was studied.The comparison of strength and hydration degree under room temperature and high temperature curing conditions shows that using appropriate high temperature curing can simulate the long-age hydration.Under the high temperature curing,the higher the cement fineness is,the more likely the compressive strength and flexural strength will decrease,which may be related to the coarsening of pore structure and the deterioration of the interfacial transition zone.Under high temperature curing,the lower the fineness of cement,the faster the subsequent hydration rate.Under high temperature curing,the strength of low-fineness cement is low in early age,but increases greatly in the subsequent age.The strength of low-fineness cement exceeds that of high-fineness cement and will not decrease in the long age,indicating that low-fineness cement has a good strength development in the long age.(3)The influence of cement fineness on the hydration process and mechanical properties of binder containing mineral admixtures was studied.The strength of binder in early age is mainly affected by the content of mineral admixtures,and the subsequent hydration rate and strength growth is affected by cement fineness and the content and the type of mineral admixtures.The strength of binder containing slag increases faster than that containing fly ash,and has a stronger refining effect on pore structure.The higher the fineness of cement is,the stronger the refining effect of slag on porosity of paste is.The higher the fineness of cement is,the faster the early age hydration rate of complex binder is.When the specific surface area of cement is increased from 300m~2/kg to 370m~2/kg,the increase in early hydration degree of complex binder is greater than that from 370m~2/kg to 440m~2/kg.