Rigid Concrete Pavement Research Articles

Influence of Asphalt-Binder Source on CAM Mix Rutting and Cracking Performance: A Laboratory Case Study

Crack attenuating mixtures, denoted as CAM, are some of the mixes commonly used in the State of Texas (USA) to mitigate reflective cracking in overlays, both in flexible-hot mix asphalt (HMA) and rigid concrete pavements. Typically designed at 98% lab density, with high quality aggregates, these fine-graded HMA mixes are rich in asphalt-binder (minimum 6.5%), predominantly using PG 76-22. In this study, three PG 76-22 asphalt-binders from three different sources (denoted as A, B, and C) were evaluated in the laboratory for their potential to meet the CAM Balanced Mix-Design (BMD) requirements when used in combination with limestone aggregates and 1% hydrated lime. Laboratory tests conducted included the Hamburg wheel tracking test (i.e., for rutting and moisture damage [stripping] evaluation), the Overlay test (i.e., for cracking evaluation), and the asphalt-binder rheology, namely the dynamic shear rheometer (DSR) and the bending beam rheometer (BBR). The corresponding results indicated that not all PG 76-22 asphalt-binders are manufactured equally and that material source has a profound influence on both the asphalt-binder rheological properties and the overall performance of the resulting HMA mix. In fact, one of the PG 76-22 asphalt-binder graded out as a PG 82-22 and could not meet the BMD performance requirements for a CAM mix-design. As part of the quality control/assurance protocols and to ensure that the right materials “as designed and specified” are utilized, the overall findings of study suggests that it is imperative that all asphalt-binders delivered to a given construction site must be sampled and tested for its rheological properties and graded accordingly. Provided high quality materials are used, the study also indicated that a CAM mix could satisfactorily be designed at a lower lab density than 98% (i.e., 96.5-97.5%); which translates into cost savings in terms of the asphalt-binder content.

Thin ECC overlay systems for rehabilitation of rigid concrete pavements

The use of rigid overlays has become increasingly popular. The main purpose of an overlay is to extend the service life of the structure and increase the structural performance and durability of a wearing surface. The superior ductility and durability characteristics of engineered cementitious composites (ECC) suggest that they could be used as an attractive alternative to conventional concrete overlay materials. In this study, the performance of ECC overlay designed at different thicknesses is investigated by laboratory experiments. Micro-silica concrete (MSC), generally used as an overlay material, is also prepared as a control mixture. The test results show that, for the same geometry and loading conditions, layered ECC beams have significantly increased both load-carrying capacity and deformability, and show better crack width control in comparison with MSC composite beams. As the overlay material, ECC is also found to be effective in eliminating the reflective cracking and delamination failure in repaired systems.

Post-cyclic settlement and tilting potential of mat foundations

A simplified procedure for the estimation of cyclic shear stresses on foundation soil layers due to interactions of seismic excitation, foundation mat and overlying structural system, incorporating both kinematic and inertial aspects was described earlier in Cetin et al. [1,2]. This simplified procedure is now used, along with laboratory-based cyclic shear and volumetric strain relationships for the assessment of cyclically induced settlement and tilting potential of mat foundations. The proposed methodology is calibrated by well-documented seismic foundation performance case histories of 3–6 story, relatively rigid residential structures with no basements. Immediately after 1999 Kocaeli and Duzce, Turkey earthquakes, foundation settlements of these case history buildings were carefully mapped relative to available elevation benchmarks, such as relatively rigid concrete pavements, drainage pipes and ditches, and entrance stairs, located in the immediate vicinity of the buildings. Tilt angles of these buildings were also mapped in orthogonal multi-directions. Relative settlement and tilt angle values vary in the range of 0–60cm and 0–5.5rad, respectively. As part of subsurface characterization studies, SPT and seismic CPTU were performed. For the retrieved disturbed and undisturbed samples, an intensive laboratory testing program including sieve analysis, Atterberg Limit, hydrometer, oedometer, static and cyclic triaxial and cyclic simple shear tests was executed. The foundation soil profiles generally consist of silty soils, sand–silt mixtures and silt–clay mixtures of SPT-N values varying in the range of 2–5 blows/30cm in the upper 5m and gradually increases up to a maximum value of 25 blows/30cm beyond depths of 5–8m. As part of the proposed framework, displacement potential indices, defined as the product of induced-cyclic strains and the thickness of soil sub-layers, were estimated, the sum of which produce settlement and tilting potentials. Then, these settlement and tilting potentials were calibrated against recorded settlement and tilt values through a statistically based calibration scheme. The proposed simplified procedure is shown to reliably and precisely capture both deviatoric and volumetric components of post-cyclic settlements, as well as tilting responses of mat foundations.

Permeable Pavement as a Hydraulic and Filtration Interface for Urban Drainage

Permeable pavement, specifically cementitious permeable pavement (CPP), is a passive structural low impact development material and green infrastructure system for rainfall-runoff control. Multifunctional engineered CPP can fulfill requirements as a load-transmitting surface while serving as a more environmentally conscious infrastructure material that functions to restore the in situ hydrology while also functioning as a passive treatment unit operation and process. As an infrastructure material; CPP reduces runoff, filters, and treats infiltrating runoff, reduces thermal pollution and temperature, provides the load-carrying capacity of conventional rigid concrete pavement, and leaches environmentally beneficial Ca and alkalinity, as compared to flexible asphalt. In this study, pore characteristics of CPP, including effective porosity (ϕe), pore size distribution and tortuosity (τ) are examined using x-ray tomography and gravimetric-geometric methods. Total porosity (ϕt) is measured and utilized as a comparative index. Results provide insight when modeling CPP as an infiltration and evaporation interface, a conveyance/storage medium for liquid and gas, and with admixtures or coatings an adsorptive-filtration medium for pollutants such as phosphorus and metals. Results indicate that high particle separation and significant hydraulic conductivities can be achieved with CPP. The effectiveness of CPP for particle removal also requires that these particle deposits are managed on a periodic basis through practices such as pavement cleaning.

Pavement Integrity Scanner to Characterize Modulus Contrast between Near-Surface and Deeper Material in Concrete Pavements

A major distress problem in rigid concrete pavements is early deterioration of near-surface layers. The quality of near-surface material governs the long-term performance of concrete pavement. If the near-surface material of the concrete layer is cured sufficiently well at an appropriate moisture and temperature, the concrete pavement system can be expected to endure fatigue loading of traffic throughout its design life span. A field measurement device, referred to as a pavement integrity scanner (PiScanner), was developed for use in quality control and quality assurance programs for concrete layers of pavement systems. PiScanner is based on the enhanced resonance search (ERS) technique, which evaluates the vertical variation of elastic modulus or compressive strength of the concrete layer in pavement systems. This information can be used in the construction period of a concrete pavement to evaluate the curing process of near-surface materials. In the implementation of the PiScanner, two design schemes were incorporated: a dedicated hardware device to perform measurements and an automated analysis algorithm to minimize user expertise required for analysis. The resulting PiScanner allows ERS measurements to be performed in about 2 min with complete analysis of the measurements in about 3 min. Two field investigations were performed on a concrete test slab and at an express highway to prove the reliability and feasibility of PiScanner. Vertical variations of elastic modulus of concrete layer were successfully obtained by PiScanner.

Sealing system selection for jointed concrete pavements – A review

Concrete pavement joints are cracks intentionally formed in the pavement to accommodate expansion and contraction due to temperature changes. Today, 98% of the agencies building and maintaining concrete roadways, and 100% of the agencies building and maintaining concrete airport pavements in the United States require the sealing of these joints for new pavements. There are two major reasons for sealing rigid pavement joints. The first is to reduce the amount of water infiltrating the pavement structure, which results in slab erosion and loss of support. The second reason is to minimize the entry of incompressible materials into the joint reservoir, resulting in point loading when slabs expand under hot temperatures and subsequent joint spalling damage. Another reason for sealing rigid pavement joints is to reduce the potential for dowel bar corrosion by reducing entrance of de-icing chemicals. The proper sealing and maintenance of concrete pavement joints thus seems to be essential for the overall performance of the rigid concrete pavement. This paper seeks to find out the factors that affect sealant life and performance and how to mitigate these to improve performance and reasonably extend sealant and thereby pavement life.

A new look at rigid concrete pavement design

A new look at rigid concrete pavement design

Discussion: A new look at rigid concrete pavement design

Discussion: A new look at rigid concrete pavement design

A new look at rigid concrete pavement design

The traditional rigid pavement model has long been firmly established as the design basis for both unreinforced and reinforced (jointed and continuous) concrete pavements. It is well proven and has served designers well for many years. However, the efficacy of pavement designs for joint spacing and reinforcement is less certain. The paper therefore compares design procedures for drying shrinkage and thermal effects for pavements with well-established design procedures for other slab structures including ground slabs and examines how pavement design could benefit from this experience and expertise. The comparisons are both useful and informative and provide a number of proposals that could clearly improve design for the long-term performance of concrete pavements, especially continuously reinforced concrete pavements.

A new look at rigid concrete pavement design

The traditional rigid pavement model has long been firmly established as the design basis for both unreinforced and reinforced (jointed and continuous) concrete pavements. It is well proven and has served designers well for many years. However, the efficacy of pavement designs for joint spacing and reinforcement is less certain. The paper therefore compares design procedures for drying shrinkage and thermal effects for pavements with well-established design procedures for other slab structures including ground slabs and examines how pavement design could benefit from this experience and expertise. The comparisons are both useful and informative and provide a number of proposals that could clearly improve design for the long-term performance of concrete pavements, especially continuously reinforced concrete pavements.

Development of Embedded Bending Member to Model Dowel Action

The development and implementation of a general, three-dimensional (3D) embedded bending member suitable for modeling dowel action is presented. The development is motivated by the desire to efficiently model rigid concrete pavement slabs with doweled joints using solid brick elements without requiring the mesh nodes to coincide with the dowel element nodes. All derivations are done with respect to an arbitrarily oriented coordinate system. The stiffness matrix of the embedded dowel element is expressed as a transformation of the unembedded dowel element stiffness matrix, eliminating the need for special integration techniques. Consideration is given to axial debonding of the dowel, as well as the nonlinear case where a gap exists between the dowel and surrounding material. Details of the object-oriented implementation of the element and its incorporation in a general, nonlinear solution strategy are presented. Convergence and parametric studies were performed using a realistic model of two rigid, concrete pavement slabs subjected to static axle loading near the joint. The results of these studies demonstrate the applicability of the element as well as indicating the potential for significant detrimental effects on doweled joint performance when gaps exist between the dowels and the pavements slabs.

Modeling Damage to Rigid Pavements Caused by Subgrade Pumping

The efficient utilization of construction and maintenance resources requires the ability to effectively predict and model subgrade pumping in rigid concrete pavements. A review of the evolution of a rigid pavement pumping model is presented in this paper. Extensions were made to an existing model to consider the effects of climate and drainage conditions, as well as soil composition on pumping magnitudes. Additional modifications permit the effect of nonconventional vehicle configurations to be considered in the calculation of pumping values. Finally, the process of calculating pumping volumes and distributing void areas was altered to provide a more realistic effect. This improved model allows proposed designs to be analyzed to determine optimum pavement characteristics. The model is implemented in a finite-element-based method for analysis of pavements that also includes the effects of concrete cracking and fatigue. Urgent need for experimental data on the size and growth of voids beneath a pavement slab is pointed out.

Condition rating of rigid pavements by neural networks

This paper discusses the development and the implementation of a neural network for the condition rating of rigid concrete pavements. The condition rating scheme employed by Oregon State Department of Transportation was used as the basis for the development of the network presented. A training set of 298 cases was used to train the network. The network adequately learned the training examples with an average training error of 0.011. A testing set of 3902 cases was used to check the generalization ability of the system. The network was able to determine the correct condition ratings with an average testing error of 0.022. The network ability of dealing with noisy data was also tested. Up to 40% noise was added to the data and introduced to the network. The results showed that the network presented could accurately identify condition rating relationships at high level of noise. Finally, a statistical hypothesis test was conducted to demonstrate the system's fault-tolerance and generalization properties. Key words: neural networks, condition rating, condition index, rigid pavements, pavement distresses, pavement maintenance, fault-tolerance, generalization, noisy data.

Pavement Design for Commercial Jet Aircraft

Requirements given in form of design charts for both rigid and flexible concrete pavements; design curves cover range of loadings for Boeing 707, Douglas DC-8 and Convair 880 commercial aircraft; strengthening of existing rigid pavements by overlays; runway and taxiway dimensional requirements for jet aircraft are not covered.