Detecting the Presence of High Water-to-Cement Ratio in Concrete Surfaces Using Highly Nonlinear Solitary Waves

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

Interpreting Falling Weight Deflectometer (FWD) Data (for Asphalt and Concrete Pavements)

4400011482, PIT WO 6Falling weight deflectometer (FWD) testing is a valuable method for assessing the structural condition of existing pavement structures. For jointed plain concrete pavements (JPCPs), FWD testing is used to detect voids, monitor joints and crack performance, and backcalculate the modulus of elasticity of the existing Portland cement concrete (PCC) and the k-value of all supporting layers. For asphalt concrete (AC) pavements, FWD testing is used to backcalculate the stiffness of each layer and to estimate the amount of damage in the existing asphalt. This report summarizes the testing protocols and data analysis procedures recommended. The report consists of three primary sections. The first section describes the testing protocols recommended for FWD data collection. The second section defines the changes proposed to current PennDOT documents (including Publication 242, Publication 408, and the PennDOT Pavement ME Design Preliminary User Input Guide) based on the findings of this study. The third section is an appendix that is divided into four separate appendices: A-Scheduling and performing FWD testing; B-Data analysis guidelines; C-Research findings and D-Laboratory and field testing

Identification of Factors Controlling the Development of Subsidence Impacts Forecasting Methodology of the I-70 Alignment over Longwall Mining of the Tunnel Ridge Mine, Washington County, Pennsylvania

In the winter of 2019, the Tunnel Ridge Mine extracted a long wall panel under I-70 in Washington County, PA. Additional longwall panels under other portions of the highway are planned in the future. The extraction of these panels can produce a subsidence basin with a maximum surface drops from 4 to more than 5-ft, the majority of which occurs within one or two months of undermining the roadway. This project investigates the influence of deforms during undermining with a focus on determining its transient characteristics, utilizes models to better understand subsidence impacts to the highway alignment, and where possible, determines how other future highway alignments could be impacted

Performance of Concrete Pavements Containing Recycled Concrete Aggregate

DTFH61-93-C-00133This interim report documents the field performance of nine concrete pavement projects that incorporate recycled concrete aggregate (RCA) in the construction of the pavement. Multiple sections were evaluated on many of the nine projects, due to perceived differences in performance levels or variations in pavement design (such as the use of virgin aggregate or the inclusion of dowel bars). All told, a total of 17 sections (of which 12 contain RCA) were subjected to an extensive field testing program, consisting of pavement condition surveys, drainage surveys, falling weight deflectometer (FWD) testing, coring, and serviceability assessments. A minimum of eight cores were retrieved from each section for laboratory evaluation of compressive strength, split tensile strength, dynamic elastic modulus, static elastic modulus, and thermal coefficient of expansion, as well as for volumetric surface testing and petrographic analyses. Each of the 17 sections included in the investigation is described in detail. Performance observations and results from the FWD and laboratory testing are presented, with emphasis on evaluating the effect of RCA on pavement performance. An overall summary is provided that synthesizes the findings and conclusions of the field testing program. A laboratory-based research effort is currently being planned to provide additional insight on the behavior of concrete mixtures using RCA. Those laboratory-based results, taken in conjunction with the results of the field testing program, will be used to produce guidelines for the design of recycled concrete mixtures and to develop recommendations for the design of concrete pavements using RCA

Cognitive rehabilitation, self-management, psychotherapeutic and caregiver support interventions in progressive neurodegenerative conditions: a scoping review

BACKGROUND: Despite their potentially significant impact, cognitive disability may be overlooked in a number of progressive neurodegenerative conditions, as other difficulties dominate the clinical picture. OBJECTIVE: We examined the extent, nature and range of the research evidence relating to cognitive rehabilitation, self-management, psychotherapeutic and caregiver support interventions in Parkinsonian disorders, multiple sclerosis (MS), frontotemporal dementias (FTD), motor neuron disease and Huntington’s disease. METHODS: Scoping review based on searches of MEDLINE and CINAHL up to 15 March 2016. RESULTS: We included 140 eligible papers. Over half of the studies, and almost all the randomised controlled trials, related to MS, while a number of single case studies described interventions for people with FTD. CR interventions addressed functional ability, communication and interaction, behaviour or memory. The majority of psychotherapy interventions involved cognitive behavioural therapy for depression or anxiety. Self-management interventions were mainly available for people with MS. There were few reports of interventions specific to caregivers. Numerous methodological challenges were identified. CONCLUSIONS: The limited range of studies for all conditions except MS suggests a need firstly to synthesise systematically the available evidence across conditions and secondly to develop well-designed studies to provide evidence about the effectiveness of CR and other psychological interventions

Evaluation of the approach used for modeling the base under jointed plain concrete pavements in the AASHTO Pavement ME Design Guide

This study evaluates the modeling of different base types under new jointed plain concrete pavements (JPCP) in the AASHTO Pavement ME Design Guide. It was found that the Pavement ME overestimated the stress in JPCP for unbonded stabilized bases and granular bases and underestimated the stress for bonded stabilized bases when compared to other models. The error in stress estimation results from modeling an unbonded base with a bonded-but-weightless base in the structural model, which is critical when the environmental loading is predominant and/or the base is stiff. Because the separation between layers that are not bonded cannot be accommodated, the behavior of a granular base cannot be accurately reflected, especially not by an elastic continuum. Keywords: Pavement ME Design, Jointed plain concrete pavement, Transverse cracking model, Stabilized base, Granular base, Finite elemen

Statistical Model for Detecting Voids for Curled or Warped Concrete Pavements

A statistical classifier is developed to interpret Falling Weight Deflectometer (FWD) data for the detection of voids under jointed concrete pavement slabs. The classifier is trained using the Seasonal Monitoring Program (SMP) sections in the Long Term Pavement Performance (LTPP) database and data from the Minnesota Road Research Facility (MnROAD). A two level cross validation process is used to assess the performance of existing void detection methods, based on a threshold of a single variable, and the LASSO classifier, which is based on several variables. Simple void detection methods based on the normalized 9,000 lb deflection were found to perform better than void detection methods based on variable deflection analysis. The LASSO classifier outperformed any of the existing void detection techniques. The LASSO classifier was validated using two field trials in Pennsylvania, and an LTPP GPS section where significant faulting had developed

A solitary wave-based sensor to monitor the setting of fresh concrete

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

Onsite strength determination for early-opening decision making of high early strength concrete pavement

High early strength (HES) concrete pavements are commonly opened to traffic within the first 24 h after construction, making early-opening decisions critical for pavement quality and traffic operations. Currently, most state departments of transportation rely on compressive strength testing for early-opening decision making. However, there laboratory tests are labor intensive, costly and not always representative of field strength development. In this study, non-destructive testing (maturity and ultrasonic tomography) was explored for faster and reliable in-situ strength estimations. An experimental section constructed using HES concrete was routinely monitored using compressive testing, maturity, and ultrasonic tomography in the first 24 h after construction. The shear wave velocity, measured using ultrasonic tomography, was able to capture the strength-gain variability within a single slab and between different slabs due to the ability to monitor several locations in a short period of time. Maturity results were consistently conservative in the first 24 h of monitoring. Results show that both maturity testing and ultrasonic tomography are able to replace or add to conventional strength testing for HES concrete pavements to facilitate making the opening decision within the first 24 h. Ultrasonic tomography proved more beneficial as a result of the device's portability, increased speed of testing, and accurate estimations of HES concrete strength for the entire pavement length