Effect Of Plant Polyphenols On Cement Hydration And Its Mechanism

Natural compound admixtures are characterized by low cost,high ecological efficiency,good biocompatibility,strong biodegradability and local availability.Among them,plant polyphenols are rich in resources,and the molecular structure contains a large number of phenolic hydroxyl groups,which are easy to react with macromolecules or metal ions,and the metal Ca2+has obvious competitive effect on the complexation reaction of plant polyphenols.In this paper,green tea(GTE)and bayberry tannin(KJ)were used as raw materials.The effects of tea polyphenols and tannin on cement hydration were analyzed by means of compressive strength,heat of hydration,XRD,TGA-DTG,MIP,SEM,The compressive strength of mortar with different concentrations of GTE and different amounts of KJ was studied.The results show that both GTE and KJ can significantly improve the compressive strength of water mortar.Among them,the optimal dosage of GTE is GTE 100,and the optimal dosage of KJ is KJ2.The compressive strength of the mortar with g GTE100 increased by 16.7%in 3d,12.2%in 7d and 18.2%in 28d,respectively;The compressive strength of KJ2 3d increased by 14.17%,the compressive strength of 7d and 28d increased by 7.40%and 14.38%respectively.In addition,plant polyphenols can be used as setting time regulator.Among them,GTE has a strong retarding effect,and KJ can adjust the setting time in different degrees.GTE25 mortar with the highest concentration did not set and harden at 3 days,and no compressive strength was detected at 7-days;Low content of KJ can shorten the setting time,and high content of KJ can prolong the setting time.Furthermore,the influence of GTE and KJ on cement hydration was analyzed from the hydration mechanism.The results show that GTE and KJ can effectively control the hydration heat of cement,reduce the hydration heat of cement and delay the time of hydration peak.The peak heat of hydration of GTE50 was 1.34 mw/g lower than that of GTEO in control group,and the peak time of hydration was 5.28 h later than that of GTEO in control group;The peak heat of hydration of KJ6 was 1.90 mw/g lower than that of KJ0,and the peak time of hydration of KJ6 was 5.09 h later than that of KJ0.In addition,the addition of GTE and KJ can refine the pore structure of mortar and make the plane CH crystal grow along the c-axis,which is helpful to improve the strength and durability of cementitious materials.Figure[36]table[12]reference[83]...