Research On Moisture Migration And Humidity Warpage Of Cement Concrete Pavement Slab

Cement concrete pavement is exposed to the natural environment for a long time.In addition to the effect of traffic load,it is also affected by conditions such as temperature and humidity in the environment.The cement concrete pavement may warp and cause the bottom of the slab to empty.After the bottom of the slab is emptied,the pavement is very easy to break under the load.At present,people’s understanding of the warpage of cement concrete pavement is mostly limited to the temperature warpage caused by uneven temperature inside the slab.However,in addition to the temperature warpage,there is also humidity warpage caused by uneven humidity in the slab.When the humidity of cement concrete changes,it will shrink.When the shrinkage of cement concrete pavement is uneven,humidity warpage will occur.At present,there are few related studies on humidity warpage,and the existing methods are not perfect for the analysis of the humidity warpage stress of cement concrete pavement.It can not accurately reflect the humidity warpage of cement concrete pavement,which makes people always underestimate the harm of humidity warpage to cement concrete pavement.Therefore,establishing an accurate and effective analysis method for the humidity warpage of cement concrete pavement is of great significance to the design of cement concrete pavement.Humidity warpage of cement concrete pavement is caused by internal humidity gradient,which is closely related to moisture migration.Therefore,when analyzing the humidity gradient,it is necessary to start with moisture migration.In view of the above situation,this paper carried out a study on moisture migration and humidity warpage inside cement concrete pavement.First,determine the theoretical model of moisture migration within cement concrete.Carry out the internal relative humidity monitoring test of cement concrete under external dry and external wet conditions.Get the relative humidity changes in different locations inside the cement concrete.Study the effects of self-drying,external drying and external wetting on the relative humidity in concrete.Secondly,the finite difference method was used to establish a numerical analysis model for the internal water migration of cement concrete.The parameter inversion analysis of water migration is carried out according to the test data.According to the inversion parameters,the numerical simulation of the water migration inside the cement concrete pavement is carried out,and the validity of the water migration model is verified.At the same time,accurate and specific humidity changes,humidity distribution and humidity gradient inside the cement concrete are obtained.Then,the humidity warpage deformation and stress analysis of the cement concrete pavement are carried out.In the existing humidity warpage stress analysis method,there is a disadvantage that the nonlinear characteristics of the humidity gradient are not considered perfectly.The theoretical calculation method of humidity warpage stress of cement concrete pavement under nonlinear humidity gradient is established.The accuracy of the theoretical calculation method is verified by the finite element simulation results.Analyze the humidity warpage and stress of cement concrete pavement under nonlinear humidity gradient.At the same time,it is compared with the existing humidity warpage stress analysis methods,and the limitations of the existing methods are pointed out.Finally,the humidity warpage measurement test of cement concrete beam specimens was carried out.It is verified that when the bottom of the slab is wet,the cement concrete slab will rapidly warp and deform upward.