| Since the Ministry of Housing and Urban-Rural Development released the "Thirteenth Five-Year Plan for Building Energy Conservation and Green Building Development" in 2017,in order to promote supply-side reform in the construction sector,the plan proposes to complete building energy conservation,intensive and efficient and green ecological building energy use Relevant tasks of the system,and in the report of the 19 th National Congress of the Communist Party of China,emphasis was also placed on building a resource-saving and environment-friendly society.At present,the domestic construction field is developing very rapidly,but at the same time of rapid development,due to the existence of concrete cracks that has a greater impact on the economy,society and environment,how to develop new ones for small structural characteristics,traffic characteristics,and environmental resource requirements Materials provide a new direction for crack repair;how to repair green cracks when they are found damaged,to ensure the full use of concrete materials,reduce waste of resources and energy consumption.Through relevant literature inquiry,raw material selection,formula test,data analysis and other technical means,a green gelled composite rapid repair material suitable for concrete cracks was developed,and its related properties were tested.The cementing material selected in this paper is composed of two active materials,denoted by A and B,then mixed with two mineral admixtures of fly ash and silica fume,and finally mixed with nano-silica(NS)to improve the related properties of repair materials.the result shows:(1)With the gradual increase of the water-to-gel ratio,the setting time(initial and final setting)and fluidity of the repairing materials have increased.In order to meet the rapid repair of the repairing materials,it is more advantageous to use a low water-to-gel ratio;As the ratio of active materials A: B increases,the setting time,fluidity,and mechanical strength all show an upward trend,which has a significant impact on the early strength.With the gradual increase of the sand-rubber ratio,the fluidity decreases,and the mechanical strength has a certain range.Increase;by adjusting the amount of fly ash to control the setting time of the repair material,so as to meet the construction requirements,as a building material with low environmental requirements,fly ash has improved environmental protection;with the increase of the amount of silica ash Increasing gradually,the coagulation time and fluidity show a downward trend,and the effect on the mechanical strength generally increases first and then decreases;with the increase of nanometer content,the coagulation time of the repair material increases first,then decreases and gradually flattens,flowing The degree decreases linearly,and the mechanical strength also increases first and then decreases.Among them,NS has a significant effect on the mechanical strength;with the increase of the admixture,the fluidity of the repairing material is improved,and the setting time is more significant.Compared with the later strength,the early strength is more obvious.(2)Based on the premise of performance and green building,the optimal ratio parameters are 0.13 water-binder ratio,0.4 sand-rubber ratio,A: B is 3: 1,fly ash content is 20%,and silica fume content is 3 %,NS content 3.5%,admixture content 3%,its 2h flexural strength is 5.5 MPa,compressive strength is 25.7 MPa,6h flexural strength is 6.1 MPa,compressive strength is 27.2 MPa,1d The flexural strength reaches 7.0 MPa,the compressive strength is 32.6 MPa,the 28 d flexural strength is 7.6 MPa,the compressive strength is 58.9 MPa;the initial setting time is 28 minutes,and the final setting time is 47 minutes.(3)By increasing the A: B ratio,reducing the water-binder ratio can effectively improve the impermeability.Adding an appropriate amount of fine aggregate can adjust the structure of the repair material,improve the compactness of the material,and then improve the impermeability.Adding an appropriate amount of nano-materials(nano-silica)can improve the performance of repair materials.As the amount of NS gradually increased,the water pressure of the three test specimens with different amounts reached the maximum value of the instrument range 4.0 MPa,but the penetration height showed a trend of decreasing first and then increasing.In addition,the appropriate amount of silica fume and fly ash can be used to fill the pores of the repair material,improve the harmful pores into harmless pores,compact the microstructure of the repair material,and improve the impermeability.(4)The degree of influence of resistance to chloride ion penetration,A: B> water-binder ratio> NS blending amount> sand-rubber ratio> silica fume blending amount> fly ash blending amount.By increasing the proportion of active material A and reducing the water-binder ratio,the reduction of the porosity of the repair material has a greater degree of influence.Within a certain range,the sand-binder ratio,silica fume content,NS content,and fly ash content increase.Promote the improvement of the microstructure of repair materials.Its mechanism of action is similar to the reason for impermeability.In particular,it is proposed that when the amount of fly ash is appropriate,the effective area of fly ash bound chloride ions can be effectively expanded,thereby increasing Resistant to chloride ion penetration.The gradual increase of the A ratio,the increase of the water-binder ratio,the increase of the sand-rubber ratio,and the increase of the amount of fly ash will cause the self-shrinkage to decrease;as the amount of NS and the amount of silica fume increase,the self-shrinkage will increase.As the water-binder ratio and sand-to-binder ratio gradually increase,the interface flexural tensile strength decreases;as the NS content gradually increases,the interface flexural strength first increases and then decreases;as the silica fume content gradually increases,The flexural tensile strength of the interface has been improved,and the increase rate is 6%,which is a larger increase.Compared with the non-doped silica fume,the increase is 93%.The small amount increases the repair material.The increase in fly ash content hinders Interface flexural strength is improved.(5)The porosity of the repair material is much smaller than that of cement mortar,and the pore size distribution of the repair material changes in a decreasing direction,which is mainly reflected by the proportion of small pores.The reason is that the incorporation of nano-materials in the repair material promotes active materials and minerals.The admixture and the like further produce a chemical reaction,and the hydration product of the network structure fills the macropores in the repair material,reduces the proportion of macropores,and makes the material denser.The pore-pore volume distribution also further illustrates the superiority of the macroscopic properties of the repair material. |
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