Studies On The Hydration Performance Of Complex Cementitious Materials

The vast use of supplementary cementitious materials in cement and concrete has great environmental benefits and considerable economic benefits,improves concrete performance as well.In this paper,complex cementitious matrials was designed based on the particle size distribution in order to control the dosage of cement and improve hardened paste performance.The hydration performance of complex cementitious matrials was studied.The physical and chemical roles various components played in the hydration process were analyzed to guide the application of complex cementitious matrials.The main research contents and relevant conclusions are as follows:(1)In order to obtain hardened paste with high strength,dense structure and less cement clinker used as well,the complex cementitious matrials design was studied.The mix proportion design is based on the principles of particles close packing and matching the chemical activity with the particle size distribution.The particle redistribution under the mixing state with water was also taken into account.(2)The hydration process of complex cementitious matrials is the combination of composite components' reactions.Different binders promote or restrict the hydration of each other.Fly ash has hysteresis effect on cement hydration in early age,lowers the reaction rate and decreases the hydration heat.Slag could accelerate the reaction process,promote the cement hydration,while reduces little hydration heat.The reaction of the mineral admixtures consumes Ca(OH)2 and decreases the alkalinity in hardened paste.In the complex system,cement has the highest reaction degree,followed by slag,and fly ash has the lowest one.(3)High temperature will increase the hydration rate,hydration heat and hydration degree of complex system,leading to higher strength and denser structure.Cement in complex cementitious materials is more sensitive to temperature rise than fly ash and slag.And raising temperature has more promoting effects on the paste performance in early age than that in late age.(4)The non-evaporable water content has a strong linear correlation relationship with the strength of hardened paste.Non-evaporable water content can characterize the chemical contribution to strength development.The pore structure of hardened paste shows remarkable characteristic apertures,and the characteristic apertures are relevant to hydration properties and products of composite binder.(5)Concrete with large quantity of slag and only 40% cement,reaches the expected strength and has better permeability resistance,carbonation resistance and volume stability than concrete with pure cement.It is possible to put this composite binder in practical application.