Study On The Performance Enhancement Method And Durability Test Of Ancient Building Mortar

Most of the ancient buildings are exposed in the wild,and they have experienced environmental effects for many years.The performance of materials has deteriorated and even suffered man-made destruction.Most of the existing ancient buildings are facing the danger of overturning or destruction,and their protection is restricted by the "minimum intervention principle".It is difficult,especially the protection of ancient masonry buildings.Based on the protection of ancient masonry buildings,this paper mainly studies the cementitious materials in ancient masonry building structures,namely the performance enhancement methods and durability enhancement techniques of glutinous rice mortar.The main research work is as follows:(1)Based on traditional lime-based glutinous rice mortar,11 sets of 660 test blocks of traditional glutinous rice mortar and performance-enhanced glutinous rice mortar were designed and prepared by adding different content of cellulose fiber and metakaolin and other performance-enhancing materials.The physical and mechanical performance test of the company obtained the reasonable dosage and performance improvement effect of performance enhancement materials.The results show that the reasonable substitution rate of metakaolin instead of lime is 25%.At this time,the compressive strength of the test block is increased by about 2 times,and the flexural strength is increased by about 1.3times.(2)Based on the 25% substitution rate of metakaolin,and with reference to related research results,after comparative analysis,the addition rate of 1% and 2% cellulose fiber was used to study the physical and mechanical properties of cellulose fiber.Impact.The results show that with the increase of cellulose fibers,the compressive strength and flexural strength of the test block both increase.Generally,when the cellulose fiber content is 1%and 2%,the compressive strength of the test block increases about 1.5 times,and the corresponding flexural strength increases about 1.6 times and 1.9 times,respectively.(3)Through the quality loss of the test block during the water freeze-thaw cycle,the relative dynamic elastic modulus loss and the number of freeze-thaw cycles,as well as the failure mode and compressive strength loss of the test block after freezing and thawing,the performance enhancement is comprehensively evaluated.The freeze-thaw resistance of the mortar.The results show that the 50% metakaolin replacement rate has the best frost resistance,and the frost resistance expressed by strength is increased by about 1.4 times,which is 2 times higher than the frost resistance without the addition of metakaolin.The frost resistance after blending with fiber The performance has been improved again.Based on the 50% metakaolin replacement rate,the freezing resistance of 1% fiber is increased by2.75 times,and the fiber content of 2% is 1.83 times higher than that of 1% fiber.On thebasis of 50% substitution rate of metakaolin,the addition of cellulose fiber improves the freezing and thawing indexes of the sample.When the addition rate of cellulose fiber is 2%,the quality and relative The dynamic elastic modulus and compressive strength loss rate were 2.13%,36%,and 26% respectively;the frost resistance with strength as an index increased by 2.2 times.(4)The durability of the mortar was evaluated more comprehensively through the salt solution freeze-thaw cycle test.The freeze-thaw cycle index is also used to characterize the anti-aging performance of the mortar in the coupled environment of freeze-thaw-salt erosion cycle.The results showed that salt erosion aggravated the damage of the test block.When the substitution rate of metakaolin was 50%,the durability of the strength index was increased by about 1.4 times,and the cellulose fiber with the addition rate of 2%significantly improved the test block ’ s performance.The resistance to corrosion by chloride and sulfate during the freeze-thaw cycle,and the corresponding durability increased by 3.3 times and 3.5 times,respectively.(5)Using nuclear magnetic resonance analysis method to analyze the pore distribution of the performance-enhanced mortar at normal age and after freeze-thaw cycles;using XRD,FTIR and SEM and other microscopic analysis methods to explore the hardening mechanism of the performance-enhancing mortar during the curing age,And the antifreeze-thaw cycle and salt erosion mechanism in the freeze-thaw age.The glutinous rice component in the mortar promotes carbonization and regulates the shape,size and crystal type of calcium carbonate crystals.Metakaolin imparts hydraulic properties to the limebased mortar,and the generated pozzolanic reaction product fills the pores and generates a denser microstructure,reduces the porosity of the test block,and corresponds to better physical and mechanical properties;The resulting hydrated gel improves the corrosion resistance of soluble salts and reduces the loss of glutinous rice components during the freezing and thawing process.The better hydrophilicity and air permeability of cellulose fibers further promote the carbonization and water of the mortar test block.The rough surface morphology enhances the bond between the fiber and the matrix,which has a good reinforcement effect on the test block.The fiber embedded in the mortar matrix effectively offsets the tensile stress caused by freezing and thawing and salt crystallization,effectively The cracking failure of the test block is improved,so that the cellulose fiber with a mixing rate of 2% and the metakaolin with a substitution rate of 50% have significantly improved the physical mechanics and durability of the test block.