The piezoelectric sensor-based electromechanical impedance (EMI) technique has been explored as a promising method to monitor the strength development and stiffness growth of concrete in past decades. The EMI method, however, has not been implemented in the field to evaluate the in-place strength gain of concrete structures or pavement. This study is one of the early works to apply EMI technology to test the real-time concrete strength of interstate pavement projects. To make it field-applicable, the concrete slab test was conducted to build the prediction function using a statistical approach. The electromechanical admittance was then employed to monitor the stiffness growth of concrete over time. The conventional cylinder test (ASTM C39) was performed as a reference to assess the accuracy of the EMI sensing method. It has been found that the EMI sensing methods and the related statistical index can effectively reflect the compressive strength gain of concrete slab at different ages. The prediction model was further used to estimate the compressive strength of highway concrete pavement. The results indicated that the EMI method could provide satisfactory results in predicting the in-place strength of concrete.

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.

Jointed plain concrete pavement (JPCP) repair slabs experience high incidences of early-age cracking due to high temperature rise and increased autogenous shrinkage of high-early-strength (HES) concrete mixtures. This paper presents an investigation to evaluate early-age cracking mitigation strategies of JPCP repair slabs. Finite element analyses were performed to understand the effects of physical phenomena leading to early-age cracking in JPCP repair slabs. While the analyses indicate the importance of concrete hydration kinetics and viscoelastic behavior on the early-age stress development in slabs, concrete moisture loss to the base was found to be the most significant phenomenon. Numerical modeling of concrete slabs was found to be useful in predicting the stress development in advance of costly field trials. Therefore, the proposed modeling approach can be applied to evaluate the performance of concrete mixtures prior to slab placement and thus improve and economize the current rigid pavement maintenance practices.

This paper presents a real case study concerning the analysis of the cracking risk of a large reinforced concrete slab-on-ground with 9.84 in. (250 mm) of thickness and approximately 9257 ft2 (860 m2) of area. It was designed to prevent effects of severe environment conditions over the life span as thermal and drying shrinkage. This slab is a pool floor without expansion joint—jointless—to avoid leakage and early deterioration of the structure. The main properties were initially estimated based on the thermal structure behavior to evaluate the volume change effect from early ages to long-term effects. The proposed solutions to reduce the volume change effects of concrete were carried out in three parts: improvements in structural design; optimization of the concrete mixture; and adjustments in the construction process. After the concrete placement, the solutions proved to satisfactorily prevent cracks, thus ensuring proper performance of the pool.

To improve the early-age cracking resistance of self-consolidating concrete (SCC), this paper investigated the effects of an expansive agent (EA), fibers, and the interaction between EA and fibers on the cracking behavior of restrained SCC caused by plastic shrinkage based on the slab test. Twenty-one types of samples were prepared, including one control group, two EA contents (6 and 8% of the mass fractions of cementitious materials), three steel fiber contents (0.25, 0.50, and 0.75% by volume), three polypropylene fiber contents (0.05, 0.10, and 0.15% by volume), three hybrid fiber contents, and nine combinations of EA (8% of the mass fraction of cementitious materials) and fibers. The initial cracking time and propagation of cracks over time were both observed. Test results indicate that an increase of EA dosage presents no significant improvement on early-age cracking resistance capability. Compared with steel fiber (SF), polypropylene fiber (PP) with equivalent fiber factors was particularly effective in reducing the nominal total crack area. In general, crack reduction factors of fiber-reinforced expansive self-consolidating concrete (FRESCC) are 70% greater than that of SCC containing fiber only. It indicates that the combination of EA and fibers enable SCC to present better early-age cracking resistance.