Mechanical Properties Of Micro-fine Steel Fibre Reinforced Magnesia-phosphate-cement Mortar And Overcoat Repair Test

When repairing broken concrete road,we usually make a(steel fiber)concrete cover overlayon the original concrete road.To some special roads such as airport runways,municipal roads,important bridges,etc.,it is more necssary for us to repair as soon as possible.Micro-steel fiber has more with unit volume and difficult to access group,the distribution more uniform in the concrete matrix,smaller size,more suitable for repair works.But due to condensation and curing time is relatively long,ordinary concrete can not meet the requirements of rapid repair.Magnesium phosphate cement has the advantages of faster condensation hardening、high early strength、hydrated at low temperature(minus 20 ℃)、high temperature resistanc、excellent adhesion with old concrete and convenient construction.This paper based on the fine modification of micro-steel fiber and the unique properties of magnesium phosphate cement to prepare micro steel fiber magnesium phosphate cement mortar and study its mechanical properties and surface repair concrete pavement performance.This article works as follows:(1)The ratio of MPC.The effects of borax and compound two kinds of retarders on the ratio of water to cement,the ratio of magnesium oxide to phosphate and the amount of retarder on the setting time and compressive strength were studied.(2)The mechanical properties of micro-steel fiber magnesium phosphate cement mortar were investigated.The effects of the types and dosage of retarder,water-cement ratio,mortar ratio,age and fiber content on the basic mechanical properties and flexural toughness were investigated.(3)Repairing the bending test of ordinary concrete slab.Based on the study of the mechanical properties of magnesium phosphate cement and the micro-steel fiber magnesium phosphate cement mortar,the proportion of the overlay layer,the overlay material and the fiber were analyzed by bending test.The amount of damage on the characteristics of the ultimate bearing capacity and deflection,etc.,to evaluate the repair effect.The paper has achieved the following results:(1)The optimum ratio of MP C is as follows: Water binder ratio is 0.12,M / P is 4,borax content is 6% orcomposite retarder content is 9%;Under the optimum amount of retarder,the compressive strenght of CR is lower than that of borax 8%,but the condensation time has doubled.(2)When the borax and composite retarder are used,the compressive strength is up to 36.2MPa(6h)、47.4MPa(12h)、50.1MPa(1d)、58.4MPa(3d)、68.2MPa(7d)and 37.3MPa(6h)、40.9MPa(12h)、46.7MPa(1d)、50.8MPa(3d)、56.2MPa(7d),bending strength is up to 9.5MPa(6h)、11.4MPa(12h)、15.6MPa(1d)、16.0MPa(3d)、17.4MPa(7d)and 12.3MPa(6h)、16.3MPa(12h)、15.3MPa(1d)、19.4MPa(3d)、22.4MPa(7d).Early high strength,suitable for road fast repair,the use of composite retarder has greater bending strength,the role of fiber toughening more obvious,the same water-cement ratio,the compound retarder slurry mixing better.(3)The load-deflection curve of material bending test has obvious deformation and hardening characteristics.The fracture properties of the specimens are toughness.The bending performance increases with the increase of age and remained stable at the age of 3d.(4)When the MSFRMM is used as the overlay,the specimen is characterized by the toughness of the multi-point and multi-fracture.After the initial crack occurs,it can still carry the crack in a certain deflection,and the load-deflection curve shows obvious strain hardening.(5)When the thickness of the overlay is the same,the bearing capacity of MSFRMM is significantly higher than that of ordinary concrete cover plate,and the deflection of damage is significantly increased,The deflection of the MSFRMM repair plate with the equivalent bearing capacity of the ordinary concrete cover is much higher than that of the ordinary concrete,and the deformation adaptability is strong and the toughness of the plate is improved obviously.(6)When the overlay is thickened,the ultimate bearing capacity of the overlay is obviously increased.When the overlay fiber increases,the ultimate loading capacity will increse,but it is not obvious when it is greater than 1.2%.