دانلود رایگان مقاله انگلیسی رابطه بین استحکام خمشی و ساختار منافذ بتن پیاده رو تحت بارهای خستگی - الزویر 2018

abstract

To explore the correlation between the flexural strength decay and the pore structure evolution of pavement concrete in seasonal frozen regions, 4 stages of an interaction experimental scheme were designed. The characteristic parameters of pore structure under the interactions were quantitatively characterized, and the correlation between the flexural strength decay and the microstructure evolution was discussed. The results show that the flexural strength of concrete under this interaction presents a parabolic attenuation trend. The specific surface area, the most probable aperture and the less harmful pores were the most important microstructure parameters affecting the flexural strength of concrete; their gray correlations were 0.8 or greater. Further, the regression analysis shows that there is a good linear relationship between the flexural strength attenuation and the pore structure evolution; the regression coefficient reaches 0.845.

5. Conclusion

In this paper, the deterioration mechanism of concrete pore structure under the interaction of fatigue loading and freeze–thaw with different stress levels has been tested. Pore structure characteristic parameters, pore size distribution and a correlation analysis of flexural strength and pore structure were discussed. The following concluding conclusions can be drawn:

(a) The flexural strength of pavement concrete shows a parabolic attenuation trend under the interaction of fatigue load and the freeze–thaw cycle. As the load stress level increases, the degree of concrete deterioration deepens. The concrete strength decreased by 28.1% (0.5 stress level) and 43.8% (0.8 stress level) in stage IV of interaction, respectively.

(b) The porosity inside pavement concrete under interaction decreases first and then increases, and the greater of load stress level is, the larger the porosity. However, there is not much attenuation difference of the specific surface area under the interaction of different stress levels, and the effect of interaction on the most probable aperture is not signifi- cant. At stage IV of interaction, the pore spacing factor reached 0.276 mm (0.5 stress level) and 0.263 mm (0.8 stress level), indication that the frost resistance of pavement concrete is seriously reduced. The effect of the freeze–thaw action on the pore spacing factor is more significant than that of the load.

(c) The more harmful pores increase continuously, while the harmless pores decrease under the interaction. Cracks are generated with the pore structure deterioration. As the interaction proceeds, the set cement becomes loose, while the pores expand and gradually connect. A large number of microcracks can be seen inside the matrix and the interface transition zone, causing serious damage to the internal structure.