Analysis Of Freeze-thaw Failure Mechanism Of Concrete Mixed With Diatomite

Freeze-thaw damage is one of the important factors of concrete structure failure in cold area.It not only affects the long-term use of roads,bridges,tunnels and other concrete structures,but also seriously affects the safe operation.In order to reduce the freeze-thaw damage of concrete structure in cold area and reduce the economic losses caused by freeze-thaw disease,this paper will propose adding diatomite from the internal structure of concrete.The method can improve the internal structure of concrete,and then improve the frost resistance of concrete structure.This research is of great significance.Based on T.C.Power’s hydrostatic and osmotic pressure theory and Kumar Mehta’s hypothesis of temperature stress,combined with the characteristics of pore structure and the law of pore icing,the internal mechanism of freeze-thaw damage of concrete structure is explored from the point of view of pore water pressure,ice pressure and temperature stress.When diatomite is combined with concrete,the corresponding physical changes and chemical reactions will occur.It is proposed that adding diatomite can change the frost resistance of concrete structure.Through freeze-thaw cycle test,concrete with different diatomite content has been damaged on the surface,the change of concrete quality and the decrease of elastic modulus for durability.Peak strain and compressive strength have been measured for the mechanical properties of concrete.It is found that a certain amount of diatomite can improve the frost resistance of C30 and C40 concrete.The C30 concrete with 1.5% diatomite and the C40 concrete with 1.0% diatomite have better performance in these five aspects,which indicates that the frost resistance of the concrete is high and the content of diatomite is reasonable.The internal porosity,critical pore size and the most probable pore size of concrete with different diatomite content were measured by scanning electron microscopy and mercury intrusion meter.The variation of pore characteristic parameters of concrete structure under different freeze-thaw cycles and the influence of different content of Diatomite on pore characteristic parameters of concrete structure were obtained by image processing technology.The freeze-thaw cycle process of concrete is simulated by ABAQUS,which is a general finite element software.The uniaxial compressive strength,temperature field and stress field are simulated.The phenomenon of freezethaw damage extending from the surface to the interior is explained from the point of view of internal stress.The effect of Diatomite on concrete structure is simulated by changing model parameters.The results show that the influence of diatomite can reduce the internal stress of specimens and improve the frost resistance of concrete structures.