Date of Award
Doctor of Philosophy
Civil, Construction, and Environmental Engineering
Portland cement concrete (PCC) slabs can be distorted into curved shapes by differences in temperature and moisture content between top and bottom surfaces. Such well-known phenomena, referred to as curling and warping, can exert tensile stresses in Jointed Plain
Concrete Pavement (JPCP) through surrounding restraints. These stresses can also be further magnified several times under repeated traffic loads and can ultimately lead to fatigue failures such as cracks impairing pavement structural performance.
To better understand curling and warping behavior of JPCP in Iowa and provide recommendations for mitigating their effects, field surveys were performed on six in-service Iowa JPCP sites of various ages, slab shapes, mix design aspects, and environmental conditions during construction during late fall 2015. An advanced stationary light detection and ranging (LiDAR) scanner was used to characterize slab curling by using its capability for making three-dimension (3D) measurements of overall slab deflection shape without need for traffic control in the field. The accuracy of the LiDAR scanner was investigated through both laboratory and field tests. Algorithms were developed to characterize degrees of curling and warping and to visualize overall slab deflection shapes in 3D, with results confirming that such a stationary LiDAR system could serve as a potentially novel method of making curling and warping measurements with acceptable accuracy and precision in accordance with ASTM standards for a class 1 profiler.
Cracking surveys were also performed on 12 Iowa 4.3 m (14 ft.) widened concrete pavement sites, including aforementioned sites, for making curling and warping measurements. These sites also, after 10 to 15 years of service life, suffered from unexpected longitudinal cracks initiated mostly from transverse joints about 0.6-1.2 m. (2-4 ft.) away from widened slab edges.Both the number and severity of longitudinal cracks were documented. Finite-element analysis (FEA) was performed to simulate stress distribution under several slab curling scenarios for different temperature gradients. It was found that the longitudinal cracks seemed primarily to be caused by a combination of excessive traffic loads, high degrees of curling and warping, inadequate support from underlying layers, pavement aging, and skewed joints. Additionally, it is also universally accepted that curling and warping of JPCP can also influence pavement functional performance in terms of pavement roughness. Eleven historical pavement elevation profiles from an Iowa Long Term Pavement Performance (LTPP) section were extracted, and then decomposed using advanced wavelet technologies into different layers of details corresponding to distinct frequency bands. Westergaard curling models were used to produce an idealized curling profile with a resulting parameter pseudo-strain gradient (PSG) based on the measured slab profile after removing certain decomposed layers corresponding to specific frequency components. The changes of PSG were then analyzed in the frequency domain and compared to International Roughens Index (IRI) values obtained through quarter-car (QC) simulation, with results that slab curling exhibited unique frequency-domain patterns with strong correlation to overall pavement roughness.
Yang, Shuo, "Investigation of curling and warping behavior of Iowa concrete pavements using advanced technologies" (2019). Graduate Theses and Dissertations. 17366.
Available for download on Saturday, March 13, 2021