Sulfate Corrocion Resistance Of Fou-ndation Concrete With Nano-Particles In Freeze-thaw Environment

In cold regions,the building foundation buried in seasonal frozen soil will be subjected to freeze-thaw damage.Furthermore,in some regions,there is a large amount of corrosive salts in soil,which will cause the erosion damageof building foundation.Under the double factors of freeze-thaw cycle and salt corrosion,the service life of building foundation is much shorter than that of building foundation under the single factor.In particular,the building foundation is under the ground,and its damage phenomenon is not easy to be discovered.Even if the damage is discovered later,it is difficult to repair.Among many corrosive salts,sulfate corrosion damage to foundation concrete is relatively serious.Therefore,it is very important to improve the sulfate corrosion resistance of foundation concrete in freeze-thaw environment.The size of nano-materials is much smaller than that of conventional materials,-and this makes them have special physical and chemical properties.Nano-materials have been used in many fields and achieved good results.In this thesis,nano-kaolin,nano-SiO2 and nano-CaCO3 are used to improve the sulfate corrosion resistance of the foundation concrete in freeze-thaw environment.The main research contents of this thesis are as follows:(1)The compressive strength test of foundation concrete is carryed out.The influence of the type and content of nano-materials on the compressive strength of foundation concrete is analyzed,and the mechanism of nano-materials improving the compressive strength of foundation concrete is revealed.(2)The salt-freeze cycle test of foundation concrete is carried out.When the number of salt-freeze cycles is equal to N,the dynamic elastic modulus and compressive strength of foundation concrete are tested.The influence of the type and content of nano-materials on the sulfate corrosion resistance of foundation concrete in freeze-thaw environment is analyzed through two evaluation indexes(compressive strength residual ratio and relative dynamic elastic modulus),and the mechanism of nano-material improving the sulfate corrosion resistance of foundation concrete in freeze-thaw environment is revealed.(3)The relationship between the compressive strength residual ratio of nano-concrete and the number of salt-freeze cycles is analyzed.The compressive strength attenuation model of nano-concrete in the salt-freeze environment is established,and the sulfate corrosion resistance life of nano-concrete in freeze-thaw environment is calculated according to the model.