Study On Durability Of New Type Of Grouting Materials Under Coupled Environment Of Thermal Damage And Sulfate Erosion

With the development of social economy,every industry in our country is in the period of rapid development.The construction industry is developing more rapidly.Nowadays,due to the limited land resources,the utilization requirements of underground space are also increasing.This also raises higher requirements for building materials.For underground buildings in special stratum,the traditional cement-based materials can not meet the requirements of underground engineering well due to the defects of their own properties.New type of grouting material has the characteristics of rapid setting,early strength,high stone rate,high water content and economic environment,which can be used as an excellent grouting material.As a new type of cement-based cementing material,the new type of grouting material has the characteristics of high stone rate,high solid water,quick setting,early strength,economic and environmental protection,etc.,and has been widely used at present.However,due to the complexity of underground environment,the new type of grouting material will encounter a variety of complex environments in use,and its durability needs to be explored on the basis of a certain age.The durability study of the new type of grouting material will be helpful to understand the change mechanism of the new type of grouting material's performance,so as to improve its durability and improve the applicability of the material.The main research contents and conclusions are as follows:In the sulfate attack test,the concentration of sulfate solution was selected as 5% and 10%,and the contrast was designed by soaking in water.Full immersion,half immersion and dry and wet circulation are selected as the soaking methods.The water cement ratio of the new type of grouting material is 4 kinds,a total of 36 groups of tests.The test blocks are tested every 28 days for each index test,a total of 252 days.The test blocks are poured with a total of 972 pieces.The influence of sulfate erosion on the appearance,quality,strength,sulfate content and microstructure of the new type grouting material was analyzed.The influence of sulfate corrosion on the appearance of materials is mainly related to solution concentration,curing age and erosion mode.The higher the sulfate concentration is,the longer the curing age is,and the more severe the corrosion will be.In immersion mode,the appearance loss caused by full immersion < half immersion < dry and wet cycle.The quality of the new type of grouting materials increased and then decreased under sulfate attack.The lower the water-cement ratio,the lower the concentration of sulfate solution,the smaller the increase and decrease of mass,whereas the increase and decrease of mass are larger.The experimental study shows that the immersion method has a greater impact on the mass loss of the new type of grouting material.In the dry and wet circulation environment with a water-cement ratio of 3.5 and a solution concentration of 10%,the mass loss of the new type of grouting material can reach 12%.Compressive strength is the main factor affecting the service performance of the new type of grouting material.Under the sulfate attack environment,the strength of the new type of grouting material will increase by about 5% to 17% in the first 84 days of curing period.Sulfuric acid ions in solution diffuse into the material under sulfate attack.The test results show that with the increase of curing age,the content of sulfuric acid in the material increases gradually,and the higher the solution concentration is,the more the content of sulfuric acid in the material is.It can be seen from the microscopic test that,after the infiltration of sulfate,it continuously crystallizes and participates in the reaction,fills the original pores of the material and continuously generates ettringite,which is the reason for the increase of material quality and strength.In the later stage,the internal void of the material is fully filled,and the continuous formation of crystals leads to the expansion and crack damage of the material,resulting in the attenuation of the mass and strength in the later stage.Under the effect of thermal damage,the selection of heat temperature 30 ?,60 ?,90 ? three temperature,and designs the condition maintenance for contrast,four water cement ratio,to block the indicators for 28 days for a test,test of 252 days,the test block,a total of 432 pieces.New type of grouting material gradually pulverizes in appearance and falls off when touched.With the increase of thermal damage age,the internal expansion of the new type of grouting material is gradually obvious,and the material is gradually broken.Thermal damage under the action of new grouting material quality gradually reduce,under 90 ? heat pollution,the quality of the material first drops rapidly,in the late fall speed gradually slow,quality gradually close to the quality of ingredients.Under the action of thermal damage,the strength of the new type grouting material decreases rapidly.Under the action of thermal damage,the microstructure of the material changes,the tiny pores inside gradually enlarge,and the strength skeleton of the material,ettringite and gel,gradually loosens.In the durability test of the new grouting material under the coupled action of heat damage and sulfate erosion,the sulfate concentration of 5%,10% and the control group of water were selected.Temperature 30 ?,60 ?,90 ? and the design standard of temperature to the control group.The indexes were tested every 28 days for a total of 252 days.The measured depth of sulfate content was 4,and a total of 972 test blocks were poured.Thermal pollution and the appearance of new grouting material under the coupled action of sulfate erosion damage than sulphate erosion effect is more serious,alone in the 90 ? heat damage effect,10% of sulfate erosion,material gradually massive spalling.Under the combined action of heat damage and sulfate solution,the mass of the material increases slowly at first,and then decreases gradually with the increase of curing age around 84 days.Compared with the single action of sulfate,the mass of the material decreased more under the combined action of heat injury and sulfate.The compressive strength of the material increases first and then decreases,and the increase range and cycle are short.As the phase increases,the strength gradually decreases,and the decrease range is large.Under the action of thermal damage,the content of sulfuric acid in the new type of grouting material was significantly higher.The higher the temperature was,the higher the concentration of sulfuric acid solution was,and the higher the content of sulfuric acid was.Under the coupling effect of heat damage and sulfate erosion,the content of sulfate in the new type of grouting material increased obviously,which led to the gradual decrease of pores in the material and the increasingly obvious sulfate crystallization in ettringite crystal.Finally through data processing software to establish the thermal pollution and sulphate erosion environment new grouting material inside of sulfate erosion prediction model,and the fitting showed that the sulfate content in the new grouting material was related to curing age,curing temperature,concentration of erosion solution and testing depth.The expression is: W=6.243+0.004×curing phase +13.332× solution concentration-0.041 ×test depth +0.008× curing temperature.Accuracy was 87 percent.