Microcosmic-test Research On Hydration Process Of Composite Cement Paste Added With Nano-particles

As the main construction material at present,concrete is of great interests to the architecture scholars and practitioners.The improvement on concrete performance is thus consistently hot topic in this area.More specifically,with a tremendous development of nanotechnology,applying the new nanometer material to modify traditional road material has become the research focus.Recently,beneficial from lower cost and increasing quality of nanometer material,the concrete material has witnessed a new developing trend that is characterized by diversified application and compounding function.Therefore,we can reasonably expect that nanometer material's new application in road engineering would have much potential.This paper is going to deal with three Nano-particles(Nano-SiO2,Nano-CaCO3,Nano-TiO2)and mineral admixtures(silica fume and fly ash),by serials of micro experiment using scanning electron microscope(SEM),X-ray diffratometer(XRD),differential scanning calorimeter(DSC).The aim of these experiments is to test the hydration reaction of cement composite pastes doped with the three nano-particles,mineral admixtures,nanometer material and mineral admixtures with the technique of two types addition and compound addition.The mechanism and research process are analyzed in this paper,with the main conclusions as follows.(1)If the ratio is limited in a certain range,the admixture of nanometer material has different effect on the hydration reaction of cement pastes.The more addition of Nano-SiO2,the more beneficial to the hydration reaction of cement composite pastes.At early period,pozzolanic reactivity of Nano-SiO2 is obviously high,but Nano-CaCO3 has certain inhibiting effect on the hydration reaction.In the late period,because of the crystal nucleus effect,the hydration reaction accelerates with more addition of Nano-CaCO3,and the effect of Nano-TiO2 on the reaction is inapparent.(2)Silica fume can markedly promote the hydration reaction of cement pastes.Fly ashhas not shown obvious hydration activity at early period,but its activity will be gradually exhibited in later stage of the hydration reaction.(3)The extent of the hydration reaction of cement composite pastes varies with different combination of two types addition of nanometer material.Nano-CaCO3 may delay the activity of Nano-SiO2 in cement pastes.Besides,the coupled effect of Nano-CaCO3 and Nano-TiO2 in cement composite pastes is similar to the effect of adding Nano-CaCO3 only.(4)In the cement composite pastes of nanometer material and mineral admixtures with the technique of two types addition and compound addition,Nano-SiO2 has a significant role in promoting the hydration reaction its cement composite pastes.(5)When water-binder ratio ranges from 0.30 to 0.38,the extent of the hydration reaction of cement composite pastes which doped with nanometer material,at the same age,is proportional with water-binder ratio.(6)The SEM experiment showed that the addition of both mineral admixtures and nanometer material can optimize the submicrostructure of cement pastes,reduce pore porosity and slenderize pore,then increase the density of pastes.