Laboratory Experimental Study On Thermal Curling Of Cement Concrete Pavement Slab

Once there is temperature gradient along the thickness of the slab, thermal curling introduced. If the curling.is completely free, there will be no stress in the slab. However, in fact, the curling of the slab is always restricted, for example, self-weitht, base course and so on. These restraints will cause thermal stress in the slab, which should be considered in the design of pavement. Although mumerous research has been carried out fousing on thermal curling and thermal stress, experimental research is needed.In this paper, indoor exprements have been done to study the thermal curling of cement concrete pavement. The infulunce of different restraints on thermal curling have been evaluated by comparing the thermal deformation of concrete slabs in different restraint condition. The main content of this paper is as followed:Firstly, the mechanical characteristics of the cement concrete have been measured, including compressive strength, bending strength, elastic modulus of compression and coefficient of thermal expansion (CTE). In the CTE study, the AASHTO TP 60 method has been conducted. The result of the experiment showed that the CTE of the concrete used in this study was 10.64×10-6/℃.Secondly, skew shearing experiment was conducted to study the characteristics of the interface between different base courses and concrete surface layer, which was evaluated by shear strength. The result showed that the shear strength of the interface between the cement stabilized sand gravel base course and concrete surface layer is 3.12 MPa, while that of the cement stabilized macadam is 4.20 MPa. Therefor, it can be concluded that the restrict of the cement stabilized macadam base course to the concrete surface layer is greater than that of cement stabilized sand gravel base course.Thirdly, by measuring the temperature distribution and deformation of the slabs lying on different semi-rigid base courses, the thermal deformation of the concrete slabs were studied. The results showed that thermal deformation of the free slab was the largest, then was the slab based on the cement stabilized sand gravel base course, and the deformation of the slab restrained by the cement stabilized nacadam base course was the least. And this result accorded with the result of skew shearing experiment. Besides that, the disadvantages in this experiment were mentioned, and suggestion were also given to fulfill the test method.At last, finite element software ANSYS was used to verify the reliabity of the experiment result, the result shows that the results of simulation and experiment were similar. Thermal stresses under the temperature gradient of 75℃/m were simulated, the result shows that thermal stress in the concrete slab restrained by cement stabilized macadam base course was 0.208MPa, while that of the slab restrained by the cement stabilized sand gravel base course was 0.182MPa. This can also claim that the restraint of cement stabilized macadam base course to the concrete is stronger than that of cement stabilized sand gravel base course.