Slab curvature, which represents the response of concrete pavement slabs to environmental loads, influences the location and magnitude of critical slab stresses and affects long-term pavement performance. The purpose of this study was to measure the changes in temperature and moisture profiles in a newly constructed concrete pavement and to determine both the overall deformed shapes of the slabs as well as the relative contributions of built-in and transient environmental effects over time. Data were collected from an instrumented jointed plain concrete pavement (JPCP) over a 2-year period. Slab curvatures were computed or predicted using measurements of temperature and moisture conditions in the slab, static strain measurements, and pavement surface profile measurements. It was found that the additional restraint provided by the dowel and tie bars does not appear to significantly reduce slab curvature resulting from daily temperature fluctuations or from reversible drying shrinkage. It does have a substa...

We describe a nondestructive evaluation (NDE) method based on the propagation of highly nonlinear solitary waves (HNSWs) to determine the excess of water on the surface of existing concrete structures. HNSWs are induced in a one-dimensional granular chain placed in contact with the concrete to be tested. The chain is part of a built-in transducer designed and assembled to exploit the dynamic interaction between the particles and the concrete. The hypothesis is that the interaction depends on the stiffness of the concrete and influences the time-of-flight of the solitary pulse reflected at the transducer/concrete interface. Two sets of experiments were conducted. In the first set, eighteen concrete cylinders with different water-to-cement (w/c) ratios were cast and tested in order to obtain baseline data to link the ratio to the time of flight. Then, sixteen short beams with fixed w/c ratio, but subject to water in excess at one surface, were cast. The novel NDE method was applied along with the conventional ultrasonic pulse velocity technique in order to determine advantages and limitations of the proposed approach. The results show that the time of flight detected the excess of water in the beams. In the future, the proposed method may be employed in the field to evaluate rapidly and reliably the condition of existing concrete structures and, in particular, concrete decks.

We present a proof-of-principle study about the use of a sensor for the nondestructive monitoring of strength development in hydrating concrete. The nondestructive evaluation technique is based on the propagation of highly nonlinear solitary waves (HNSWs), which are non-dispersive mechanical waves that can form and travel in highly nonlinear systems, such as one-dimensional particle chains. A built-in transducer is adopted to excite and detect the HNSWs. The waves are partially reflected at the transducer/concrete interface and partially transmitted into the concrete. The time-of-flight and the amplitude of the waves reflected at the interface are measured and analyzed with respect to the hydration time, and correlated to the initial and final set times established by the penetration test (ASTM C 403). The results show that certain features of the HNSWs change as the concrete curing progresses indicating that it has the potential of being an efficient, cost-effective tool for monitoring strengths/stiffness development.

This research evaluates the ability of the Mechanistic–Empirical Pavement Design Guide (MEPDG) to accurately predict the performance of jointed plain concrete pavements (JPCPs). This is accomplished by comparing predicted performances with observed performances for the in-service mainline test cells at Mn/ROAD. These comparisons indicate that MEPDG performance predictions for JPCP are most accurate when the default (constant) built-in equivalent temperature difference of − 5.5°C is used instead of a site-dependent value. It appears that significant portions of the error of estimation can be explained by the sensitivity of the performance models to variability in hardened concrete properties (modulus of rupture, modulus of elasticity and coefficient of thermal expansion) and pavement structural features (slab thickness, joint spacing, subbase type and bond condition). Predictions of slab cracking were found to be highly sensitive to these parameters. In addition, the MEPDG cracking model seemed not to fit local cracking observations for the Minnesota test cells. New calibration factors are needed to more accurately predict Minnesota JPCP slab cracking. This study also included comparisons of predicted service lives for the Mn/ROAD test cells using different design methodologies and as-built input parameters. In most cases considered, the MEPDG predicted longer service lives than did the 1993 AASHTO procedure. The MEDPG also predicted longer service lives than the PCA procedure for the 5-year cells but shorter service lives for the 10-year cells. This infers that, when holding service life constant, the MEPDG generally results in thinner concrete pavement sections than the 1993 AASHTO procedure.

The reasonableness of the models in the Mechanistic-empirical Pavement Design Guide (MEPDG) used to predict the performance of the continuously reinforced concrete pavements (CRCPs) was evaluated in this study. The MEPDG punchout, crack width and spacing and load transfer efficiency (LTE) models were evaluated through a factorial sensitivity study. The input matrix was defined to reflect ‘real-world’ design situations. It was found that, contrary to the 1993 American Association of State Highways and Transportation Officials (AASHTO) Design Guide, crack width must be below 0.5 mm to maintain adequate performance. Additionally, based on the performance predictions from the MEPDG, a crack spacing of less than 1.8 m ensures a crack width of less than 0.5 mm, which is another contradiction with the approach in the 1993 Guide.

Bonded concrete overlays on asphalt pavement (BCOA) offer a rehabilitation method for moderately distressed asphalt pavements. A performance review of the BCOA projects constructed in different parts of the United States suggests that the main distresses, such as longitudinal and corner cracks, develop primarily as a result of debonding of the asphalt layer from the concrete overlay. Debonding, which reduces the contribution from the underlying asphalt layer, increases the stress in the concrete layer, leading to the development of cracks. In this study, a finite-element analysis was performed to investigate the influence of the interface bond on the load-induced stress for 76-mm (3-in.), 102-mm (4-in.), and 152-mm (6-in.) concrete overlays. It was found that debonding can increase the magnitude of the load-induced stress in the concrete by up to 40–55%. Maintaining high joint load transfer efficiency (LTE) reduces the tensile stress at the interface that contributes to debonding. Relationships were developed between LTE and debonding stress for a range of overlay designs. The findings from this study can be used to facilitate the integration of debonding models in the mechanistic-empirical design procedure for BCOA. The results from this investigation can also be used in establishing a reasonable range of the target values for interface bond strength needed when constructing BCOA to ensure good performance.