Study On Properties And Mechanism Of Organic Silicon Modified Cement Mortar

The modified cement slurry and cement mortar were prepared by adding three kinds of organic silicon?KH550,KH560 and KH570?and three kinds of organic silicon?1%,3%and 5%?,and the working performance of the modified cement slurry was analyzed comprehensively.The mechanical and physical properties of cement mortar were characterized by X-ray diffractometer?XRD?and Fourier transform infrared spectroscopy?FT-IR?.The pore structure of modified cement mortar was characterized by scanning electron microscopy?SEM?and N₂ adsorption experiment,and the mechanism of silicone modification was revealed.The main research results are as follows:?1?Thestandardconsistencywaterconsumption,setting time,fluidity,water loss and water retention of blank samples and modified cement slurry with different kinds and amounts organic silicon were analyzed.The results show that for the same organic silicon modified cement slurry,with the increase of the content,the standard consistency water consumption of the cement slurry decreases gradually,the initial setting time and the final setting time increase,and for the same amount of modified cement slurry,the initial setting time and the final setting time are increasing.The initial setting time and final setting time are as follows:KH550-doped organic silicon?SPCP1?<KH560-doped organic silicon?SPCP2?<KH570-doped silicone?SPCP3?;organic silicon can obviously increase the water loss and fluidity of cement slurry.Due to the retarding effect of organic silicon and the action of self-hydrophobicity,the water retention rate is decreased and the working performance is increased.?2?The compressive strength and the flexural strength of the modified cement mortar with different amounts of organic silicon modified cement mortar for 3d,7d,14d and 28d,as well as the water absorption of the capillary pores,the volume density,consistency and porosity of the new mixed mortar were analyzed.The results show that the mechanical strength of the modified cement mortar decreases with the addition of silicone,and increases with the increase of curing age.The capillary water absorption test show that the addition of organic silicon effectively enhanced the hydrophobicity of cement mortar.The bulk density of fresh mortar decreases with the addition of organic silicon.The density of cement mortar increases and the porosity of cement mortar increases with the addition of organic silicon.The porosity of the modified cement mortar with the same amount of organic silicon is from small to large:KH550-doped organic silicon?SPM1?<KH560-doped organic silicon?SPM2?<KH570-doped organic silicon?SPM3?.?3?The influence of organic silicon on the micro-structure of modified cement mortar at different ages was analyzed by degree of hydration experiment and XRD,FT-IR,SEM,N₂ adsorption.According to the experiment of degree of hydration,the hydration of cement was inhibited by the addition of organic silicon.The XRD and FT-IR analysis of the modified cement slurry at different ages showed that the addition of organic silicon do not change the types of hydration products,and there are no new substances in each curing period,but the organic silicon can delay the occurrence time of hydration products,and the addition of organic silicon do not change the type of hydration products,and there is no new material formation in each curing period,which has obvious retarding effect.SEM analysis of different ages shows that in the same age,a large amount of hydrated calcium silicate gel,a small amount of calcium hydroxide and ettringite have been produced in the interior of the blank cement mortar in the same age,and a small amount of calcium hydroxide and ettringite have been produced in the interior of the blank cement mortar.However,the hydration products of the modified cement mortar are relatively few and the space structure is larger,and the internal structure is relatively loose.Using N₂ adsorption test,it was found that the cumulative pore volume and maximum adsorption capacity of cement mortar are increased by the addition of organic silicon,and the increasing effect is gradually enhanced with the increase of the content of organic silicon.