| Concrete structures in hydraulic buildings are subject to varying degrees of damage under the influence of high velocity sand-laden water flows and nudge impacts,and these damages are likely to produce further aggravation of other diseases and damages to the concrete structure,posing a number of hidden dangers.In this paper,epoxy resin is selected as the repair base material and epoxy mortar as the repair mortar to investigate the bonding and durability of epoxy mortar for repairing hydraulic concrete.The main research content of this paper and the conclusions are as follows:(1)The influence of parameters such as mastic-solid ratio,interfacial agent and curing age on the own mechanical properties of epoxy mortar and the bonding performance of the interface was revealed.The orthogonal test found that: the choice of cement-solid ratio can effectively improve the bonding performance and durability of the interface between epoxy mortar and hydraulic concrete,and the proportion of filler should be controlled within the appropriate range;the choice of interface agent can not only wrap the exposed aggregates to make them better bonded with epoxy mortar but also fill the micro-cracks and pores inside the concrete;the epoxy mortar with the cement-solid ratio of 1:2.0 tends to stabilize with the increase of curing age,and does not show high early strength.The bond strength tends to stabilise as the curing age increases and does not appear to be high in early strength;the epoxy mortar is intact in acid,alkali and salt solutions,but bends in some positions in the UV ageing ability test,so it is recommended that more attention be paid to temperature and light control during the maintenance of the epoxy mortar.(2)Considering the environmental changes of wet and high temperature often encountered in hydraulic concrete,the influence law of the thermal expansion property of epoxy mortar and the change of moisture content of the substrate on the interfacial bonding performance was investigated.The test results found that: by changing the filler ratio of epoxy mortar can effectively match the thermal expansion coefficient of epoxy mortar and concrete,thus reducing the temperature stress of both due to different deformation,which can reduce the possibility of micro-cracks generated by temperature stress,when the adhesive-solid ratio is 1:2.0,the thermal expansion coefficient of epoxy mortar is lower,and the difference between the thermal expansion coefficient of epoxy mortar and concrete is smaller at this time,which is applicable in the temperature-20℃~ 60℃ environment is applicable;the bond strength of epoxy mortar and substrate,decreases with the increase of moisture,when the moisture content of substrate is0%~50%,it can meet the performance conditions of continuing work after repair;it is deduced from the microscopic perspective that when the substrate is completely saturated,the porosity and cracks of the substrate are large,epoxy mortar can only enhance the mechanical strength at the interface,the difference between the two strengths is too large,further leading to interface The difference in strength between the two is too great,leading to further interface failure.In contrast,when the matrix is not saturated,pores and fissures at the interface are rare and the epoxy mortar fills the tiny fissures by gravity,which is also consistent with the test results in the previous paper;the epoxy mortar does not reduce the bonding performance of its repair mortar under long-term wet conditions,which proves the possibility of epoxy mortar repairing hydraulic concrete.(3)The correlations of the factors influencing the bonding performance of the interface were elucidated by calculating the grey integrated correlations of the bond strength with various influencing factors.The results: gum-solid ratio > interfacial agent > maintenance age,in general agreement with the ranking of the grey absolute and grey relative correlations.The choice of cement-solid ratio determines the strength and durability of the repair mortar,which in turn affects the bond strength of the concrete,which is a key factor in improving the strength and toughness of the epoxy mortar;the choice of interface agent can change the roughness of the concrete,which in turn improves the bond strength between the repair mortar and the concrete;while the curing age only improves the strength of the repair mortar,which does not directly affect the bond strength of the concrete,and Concrete is influenced by many factors during the curing age and has a complex structure of its own,thus the lowest integrated grey correlation.(4)The construction process method for repairing hydraulic concrete with epoxy mortar was improved.The relatively suitable mixing order is: thinner → epoxy resin → curing agent →cement & standard sand;the best mixing time of the optional epoxy mortar is 3.5min;the shrinkage rate of epoxy mortar with 1:2.0 and 1:3.0 cement-solid ratio is more stable;the resting time is controlled within 60 min to have less influence on the performance of epoxy mortar;the thickness of epoxy resin interface agent should generally be controlled at about 2mm;the depth of the damaged surface is less than 2mm,and the damaged surface can be repaired directly with epoxy interface agent.When the depth of the damaged surface is less than 2mm,it can be repaired directly with epoxy interface agent,and for the damaged surface which is greater than2 mm and less than 20 mm,it will be filled with interface agent first,and then repaired with epoxy mortar.The maintenance method has a certain influence on the strength formation of the epoxy mortar,the combination of 7d wet maintenance and 21 d standard maintenance has a higher compressive strength and bond strength than the other four maintenance methods. |
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