| With the development of high-strength concrete and prefabricated buildings,the requirement for better performance of repairing mortar is increasing.The polymer repairing mortar has higher toughness and better durability than ordinary repairing mortar,but it also reduces the compressive strength and elastic modulus,which further resulting in lower compatibility and durability of concrete structure,affecting the normal use of concrete structures and even endangering personal safety.Therefore,it is necessary to study the material composition and process of the polymer repairing mortar to improve its self-performance and interface bond quality.Ten different sand gradations is designed by uniform test method.The influence of sand gradation on mortar strength is analyzed.The bulk density and fineness modulus are proposed to choose an optimal gradation.The effects of five admixtures(polycarboxylate superplasticizer,polypropylene fiber,redispersible rubber powder,silica fume and UEA expansion agent)on the consistency,deformation,compressive strength and flexural strength of polymer repairing mortar are further studied.The resistance strain gauge is directly installed on the surface of repairing mortar to monitor its deformation.In order to improve the bonding quality of the repairing interface,two experiment groups are designed,with seven kinds of expansion agent polymer repairing mortar are used to fill the 10 cm grooves in cubic concrete structures.The deformation law of the repairing mortar and the changing mechanism of compressive strength of repaired concrete structure are studied.Next,a graphite and epoxy composite is prepared and the effect of graphite content on microstructure of the composite is studied.The composite material is used to replace the redispersible rubber powder to make the repairing mortar.The compressive strength,flexural strength,bending bond strength,freeze-thaw durability and the corrosive effects of hydrochloric acid resistance of the composite materials with different graphite content are investigated.Finally,the prepared process of filling repairing mortar and interface repairing mortar are optimized,which can provide a set of implementation process for the prepared repairing mortar.Results show that the formulated mortar has the highest strength when the gradations of 10-40,40-80,and 80-100 mesh accounted for 40.84%,26.62%,and 32.54% respectively,which also had the highest bulk density and belonged to medium sand.The mechanical properties of repairing mortar are obviously improved when the amount of water reducing agent is 0.6%;0.1% of the fiber can effectively improve the flexural strength of repairing mortar and inhibit its shrinkage,but the consistency decreases after the amount exceeds 0.1%.The rubber powder reduces the shrinkage of repairing mortar,and 3% of rubber powder obviously increases the flexural strength of repairing mortar but reduces the compressive strength;4% of the silica fume significantly improves the compressive strength and flexural strength of repairing mortar.The compressive strength of repaired concrete has continuously improvement when the amount of expansion agent is less than 8%,and the compressive strength of the repaired concrete structure without the film reaches 38.4 MPa,while the compressive strength of repaired concrete structure with the film is lower,which is caused by the separation between repairing mortar and the concrete groove during the compression process.The finite element simulation shows that the bonding quality of the repairing mortar and concrete interface is the highest under 8% dosage of expansion agent.The strength and modulus of graphite and epoxy composites increase with the increase of graphite content.The microstructure of 6% and 9% graphite is dense.Compared with epoxy repairing mortar,the compressive strength and bending bond strength of composite modified mortar increase by 20.4% and 52.4%,and the flexural strength and durability are also slightly improved.The growth of ettringite crystal is more uniform while the compactness of repairing mortar is also improved. |
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