International Concrete Abstracts Portal

Cross-tensioned prestressed concrete pavement (CTPCP) has superior mechanical and durable performance over ordinary concrete pavement. An approximate model to predict stresses and displacement of CTPCP under temperature loading is developed. Elasticplastic model is adopted to describe the performance of sliding layer between CTPCP and subgrade. The stresses in concrete are divided into friction introduced, curling, and prestressed components. Friction introduced component is obtained with the equivalent equation of CTPCP and curling component is obtained with Westergaard solution for concrete pavement with infinite length but finite width. Furthermore, influences of parameters, including length and thickness of slab, elastic modulus of concrete, frictional coefficient, space, angle and position of prestressed strands and reaction modulus of subgrade, on stresses and displacements are discussed. Results show that decreasing length and thickness of pavement, frictional coefficient, and elastic modulus of concrete are effective ways to reduce stress under temperature loading. Furthermore, decreasing space but increasing diameter of prestressed strands is another way to prevent too large tensile stress in CTPCP. Additionally, it seems to be more concise that the perfect plastic model is adopted to predict friction introduced stress in engineering application after comparative analysis of difference between to bilinear model and plastic model.

Continuously reinforced concrete pavement (CRCP) has superior durability and mechanical performance over jointed plain concrete pavement (JPCP) without preset joints. However, there are many small cracks in CRCP under environmental loading. Crack width of CRCP is the one of most important factors for pavement design, and it directly influences durability. Therefore, an approximate model is developed to predict crack width and stresses of CRCP under temperature loading. Furthermore, the effect of influenced parameters on crack width is discussed. The results show that axial components account for a great proportion of thermal stress, compared to curling stress. Reinforcement ratio and diameter of reinforcement have significant influence on crack width. Increasing reinforcement ratio, while decreasing diameter of reinforcement can decrease crack width. Adhesive strength between concrete and reinforcement influences crack width, too. Higher adhesive strength can reduce crack width. Moreover, thicknesses of pavement, tensile strength, and elastic modulus of concrete also have an effect on crack width. Improvement of the tensile strength of concrete would widen the crack width, but lengthen the spacing between adjacent cracks. Both thicker pavement and higher elastic modulus of concrete introduce wider crack widths but improve bearing capacity. Therefore, a larger reinforcement ratio but smaller diameter of reinforcement with deformation, and a lower elastic modulus of concrete pavement with larger thickness are recommended.

Thin concrete pavement overlay placed on the top of flexible pavements is referred to as a thin whitetopping (TWT) pavement, which is one of the rehabilitation treatments for deteriorated flexible pavements. The primary goal of this study is to evaluate the fatigue performance of full-scale TWT pavement due to repeated traffic loading. Super-accelerated pavement (SAP) tests on full-scale TWT concrete slabs were performed under static and constant cyclic loading. The stationary dynamic deflectometer (SDD) (a truck-mounted SAP testing device) was used to statically and dynamically load the TWT slabs. To monitor the response of the TWT slabs, accelerometers and linear variable differential transformers (LVDTs) were installed and the dynamic displacements of slabs were recorded during the entire testing period. The test results show that the tested slabs have dynamic displacement peaks around the number of load repetitions corresponding to the first visible cracks. The dynamic displacement increased at a higher rate after the occurrences of the first visible crack. In addition, the tested slabs showed a stress redistribution phenomenon during the crack propagation. The concepts of the stress level and equivalent fatigue life were used to eliminate, in part, influences of other factors (that is, the water-cement ratio [w/c] and aggregate type and gradation) and correct the effect of different stress ratios, respectively. The S-N curve developed from this study was very close to Thompson and Barenburg’s S-N curve after the application of the equivalent fatigue-life concept.

As portland cement concrete (PCC) pavements cure, permanent deformations develop from nonuniform temperature and moisture conditions in the slabs. Subsequent daily and seasonal environmental cycling cause the slabs to expand and contract horizontally with changes in average temperature and moisture conditions, and curl and warp vertically as temperature and moisture gradients change through the slab depth. These deformations affect the magnitude of load transferred to adjacent slabs and vertical support provided by the underlying base layer. Dowel bars are often placed at pavement joints to facilitate load transfer. Two 3.66 m (12 ft) wide, by 13.72 m (45 ft) long, by 254 mm (10 in.) thick concrete pavements were constructed in the Ohio Accelerated Pavement Loading Facility (APLF). Transverse contraction joints were placed at 4.57 m (15 ft) intervals to create three contiguous 4.57 m (15 ft) long slabs in each pavement. Dowel bars were added to the joints in one pavement, and the other pavement was left undoweled. Pavement deformation, response, and temperature were monitored over a range of controlled environmental conditions with sensors installed at the time of construction. Large upward vertical deformations were observed along the slab edges early in the curing cycle, and these deformations continued to increase throughout the duration of the tests. The slightly smaller vertical movements observed in the doweled pavement were attributed to the presence of the dowel bars.

Water is free to evaporate from the top surface of a concrete pavement during its service life, while the bottom surface is covered. The difference in humidity results in variations through the slab thickness in the modulus of elasticity of concrete, its creep coefficient, and the amount of shrinkage. These time-dependent variations produce, in the inner zone of a prestressed concrete pavement, compressive and tensile stresses at the bottom and top surfaces, respectively. The method of analysis presented in this paper is simple to apply and use in practice when the parameters related to the properties of concrete are known. The same equations used for prestressed pavements are applicable to nonprestressed pavements and slabs on grade.