| The slab track is the main track form of high-speed railways.CA mortar is an important part of the slab track.Its properties greatly affects the performance of the track structure.At present,the interlayer separation between the CA mortar and concrete track slabs is one of the major damages to the track structure,which has a great influence on the mechanical properties and durability of the track structure.In this study,CA mortar-concrete composite specimens were used as the research object,and the microstructure of CA mortar was changed by adding admixtures to systematically study the variation of interfacial bonding strength and mechanical properties of composite specimens under different temperature fields.Moreover,the effects of different admixtures on the acid and salt corrosion resistance of CA paste were explored,and the corrosion mechanism of acid and salt was revealed from a microscopic point of view.Finally,theoretical guidance was provided to prevent the occurrence of interlayer separation.The main work and conclusions of the research are as follows:(1)The interfacial bonding strength between CA mortar and concrete is mainly provided by the mechanical interlocking forces between the cement hydrates and the concrete and the adhesion forces of asphalt.At any A/C,the bonding strength increased after the PI type latex or expansion agent was incorporated.After the P?-type latex was incorporated,the bonding strength was almost unchanged at low A/C,and the bonding strength was increased at high A/C.After temperature cycles,the interfacial bonding strength of the composite specimens decreased;the larger the expansion agent content,the greater the decrease in bonding strength.At low A/C,the incorporation of PI would increase the temperature sensitivity of bonding strength.On the contrary,the incorporation of PI would weaken the effect of temperature on bonding strength at high A/C.(2)The composite specimens of CA mortar and concrete mainly show two failure modes:the overall bending failure(referred to as type A failure)and the mortar layer de-bonding failure(referred to as type B failure).The failure mode is determined by the interfacial bonding strength and the elastic modulus of the mortar.At low A/C,the interfacial bonding strength dominates.The elastic modulus of the CA mortar contribute a lot while at high A/C,.At low A/C,the composite specimens mainly showed type A failure.And at high A/C,the composite specimens mainly showed type B failure.After temperature cycles,the failure mode of the composite specimen was B-type failure in most cases.(3)The addition of admixtures changes the interfacial bonding strength andflexural strength of CA mortar,which further affects the flexural strength of composite specimens.With the increase of the amount of PI latex and expansion agent,the flexural strength of composite specimens increased significantly.After temperature cycles,the flexural strength of composite specimens decreased.The greater the PI content,the greater the reduction in flexural strength.At low A/C,the incorporation of expansion agent weakened the temperature sensitivity of the flexural strength.At high A/C,the incorporation of expansion agent strengthed the effect of temperature.(4)At low A/C,with the incorporation of PI,the acid anti-corrosion coefficient increased first and then decreased,while the acid anti-corrosion coefficient decreased first and then increased when PII is incorporated.The addition of the latex can significantly reduced the salt anti-corrosion coefficient of the specimen.After incorporating the expansion agent,the acid anti-corrosion coefficient and salt anti-corrosion coefficient all decreased.At high A/C,the incorporation of the latex can significantly increased the acid and salt anti-corrosion coefficient,and the effect of the PII latex was more pronounced.With the increased of the expansion agent,the acid and salt anti-corrosion coefficient increased first and then decreased. |
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