The Matching Ratio Design And Performance Exploration Of Modified Cement-based Repair Mortar

As the old buildings close to or reach the design reference period,old buildings are seriously damaged due to external environment or internal defects,structural safety is affected,so some of them should be repaired or reinforced.At present security repair materials have a great development,modified repair mortar is one of security repair materials,which is high-strength,small-shrinkage,good-work performance Modified repair mortar is widely used in the repairing and reinforcing of building structure.Repair mortar which is high-strength,small-shrinkage,well-ductility and good-work performance needs to be researched on.In this paper,the results about mechanic-performance,work-performance,shrinkage-rate are given.The influence factors include cement-aggregate ratio,water-binder ratio,quartz sand gradation,hydrated blended cement system,mineral admixture,polymer and so on.The optimum mixture ratio about modified cement-based repair mortar is proposed.The main contents are as follows:(1)The effect of factors including cement-aggregate ratio,water-binder ratio,quartz sand gradation,cellulose on mortar mechanical performance and working performance are researched so Mortar base mixture ratio is determined.The results show that,with the increase of sand cement ratio,flexural strength and compressive strength of mortar is gradually reduced.When mastic ratio increases from 1.5 to 2.5,compressive strength and flexural strength of mortar are reduced by 28.44%and 28.44%respectively.Consistency of mortar decreases with the increase of cement-aggregate ratio.Consistency of mortar increases with the increase of water-binder ratio.40～70 mesh,70～140 mesh quartz sand with different mixing ratio,with the increase of proportion of 40～70 mesh quartz sand,compressive strength and flexural strength of mortar shows growth before they are reduced.the consistency of mortar increase.When two quartz sand ratios is 1:1,compressive strength and flexural strength of mortar is highest,Strength is 88.6 MPa and 15.9 MPa respectively.When the cellulose content increased from 0 to 0.1%,initial consistency of mortar decrease gradually,loss of consistency is reduced after half an hour.(2)The effect of ordinary portland cement-sulphur aluminate cement-gypsum composite cement system on mortar mechanical properties,setting time,shrinkage are researched.Substitution amount of sulphur aluminate cement and contents of gypsum are determined.The results show that,when ordinary portland cement:sulphur aluminate cement ratio increases from 10:1 to 6:1,compressive strength and flexural strength of mortar decrease gradually,The initial setting time reduced from 45 min to 18 min.Shrinkage of mortar decreases gradually when the dosage of anhydrite increases from 3%to 8%,minimum shrinkage of mortar is 0.07%as anhydrous gypsum content is 8%.When mixed dihydrate gypsum and anhydrite replace quantity reach to 5%,with the increase of the proportion of dihydrate gypsum,compressive strength and flexural strength of mortar decreases gradually,initial setting time extends gradually.(3)The effect of fly ash,silicon ash and mineral powder on mortar mechanical properties,consistency,bibulous rate are researched by orthogonal test.Optimum content of mineral admixtures is determined.The results show that,when fly ash dosage increases from 5%to 20%,mortar consistency gradually increases,28d compressive strength and flexural strength decreases.When silica fume dosage increases from 2%to 8%,28d,compressive strength and flexural strength increases.From the comprehensive performance of mortar,the best dosage of fly ash,silicon ash and mineral powder are 5%,6%,15%.(4)The effect of factors including high styrene rubber,waterborne epoxy resin emulsion,redispersible powder on mortar modification effect are researched.Optimum content of polymer is determined.The results show that,when content of polymer increases from 2%to 8%,the bond strength of mortar rises gradually,compression flexure ratio reduces.When content of waterborne epoxy resin emulsion reaches to 6%,the bond strength of mortar is 2.32MPa,which increases by 79.84%compared with ordinary mortar strength 1.28 MPa.The mixed polymer can make mortar compressive strength and flexural strength decreases,and improve the durability of cement mortar a certain extent.(5)The optimum mixture ratio is determined in this paper.The mixture ratio is are as follows:cement-aggregate ratio is 0.28;water-binder ratio is 1.5;quartz sand proportion of 40～70 mesh:70～140 mesh is 1:1;proportion of ordinary portland cement:sulphur aluminate cement is 8:1;gypsum content is 8%;fly ash replacement is 5%;silica fume content is 6%;ash content is 15%;content of waterborne epoxy resin emulsion is 6%.