Re-evaluation of the Kentucky Flexible Pavement Design Criterion

Prior to 1948, the criterion in Kentucky for designing the thickness of bituminous pavements was based upon a modified laboratory CBR and the 1942 curves developed by the California Department of Highways. In 1948, the Materials Research Laboratory reported: An Investigation of Field and Laboratory Methods for Evaluating Sub-grade Support in the Design of Highway Flexible Pavement. Included in that report as a recommended method of thickness design for use in Kentucky was a set of curves based upon an empirical relationship between minimum laboratory CBR and observed pavement performance. These five curves accounted for traffic groups up to 10,000,000 EWL\u27s. Since that time six additional curves have been included in the de sign charts for EWL groups up to 320,000,000. These additional curves were determined by extrapolation of the results from the 1948 study. Early in 1957, an evaluation of the design method was under taken. The basis for this re-evaluation was a statistical comparison of actual pavement performances with the designed life as anticipated or predicted by the design curves currently in use. On this basis, projects were selected, design records assembled, performances surveyed, and the data analyzed. Selected pavements which had been designed by the method developed in the 1948 study were checked for performance by visual survey, by roughness measurements, by measurements of rutting, by measurements of loaded-deflection with the Benkelman Beam, and by opening pavements for observation and sampling. Flexible base types studied included water bound macadam, bituminous concrete, granular dense graded aggregate and combinations. Laboratory evaluation on basis of bearing tests were made. The visual survey established a range of performance. Road roughness measurements were related to CBR but no attempt was made to draw design curves from this data since it could be greatly affected by factors not related to structural design. Pavements opened for inspection revealed permanent deformation in the upper layers of the system as well as intrusions of subgrade in waterbound base courses. An alternate method of design based on limiting deflection under load was developed from the Benkelman Beam measurements. Curves drawn from this data indicate a need for a slightly greater thickness than provided by the 1948 curves

Criteria for Design of Pavement Thicknesses, Kentucky Interstate Highways

The Kentucky Department of Highways, in 1946, sought a more systematic criteria and basis for designing the thickness of bituminous concrete pavements. The Research Division was authorized to pursue this work and to develop the criterion. These efforts were embodied in a report (1) to the Department, which offered a system of design based upon CBR\u27s and EWL\u27s. EWL\u27s were computed originally for a 10-yr. period but this practice was revised in 1954, to encompass 20-yr. traffic (more realistic with respect to average road life). Then, in 1957, the Department requested a re-evaluation of the criteria from the standpoint of experience and performance of pavements designed thereby. This re-study and recommendations was reported to the Department and to the Highway Research Board (2)(3). A copy of current design chart is shown on the following page (Fig. 20, ref. 2 and 3)

Kentucky’s Pavement Management System

Pavement management concepts are discussed, and a method is presented illustrating the required data and its use to accumulate EAL\u27s annually for comparison with the design EAL. This method can be used to determine overlay priorities, overlay design thicknesses, and financing schedules. A discussion of automatic feedback of field data is presented. Pavement condition reports should be analyzed separately to prevent improper adjustments in the design system due to causes of failure other than normal fatigue. An overlay, whether for extending service life or improving skid resistance, provides an additional structural thickness and will modify the design life. Preparation of the R-R-R cost estimates in the fall of 1976 offered the opportunity, and necessity, to implement a pavement management scheme. The methodology used to prepare the cost estimates are discussed in relation to overlay design and scheduling of resurfacing on the Interstate System in Kentucky. There are compounding and confounding factors which may distort pavement performance and confuse a pavement management scheme based only on the structural adequacy of the pavement. Such factors and influences as D-cracking, expansive aggregates, ditching, skid resistance, roughness, and rutting are discussed

Ten Rural Highway Base Stabilization Projects

During the last week o£ September, 1956, the Division of Rural Highways requested assistance from the Research Division in conducting a series of ten experimental base stabilization projects which were to be geared more-or-less to a practical rural roads development program in which existing soils and local granular materials might be most advantageously treated and stabilized to provide fairly low cost base courses and surfaces, adequate for light rural traffic. The idea of actually constructing a base and bituminous surface for this type of road would represent a refinement over the traditional traffic-bound base type of construction which usually serves as a preliminary to light bituminous surfacing. While the traffic-bound type of construction has been used effectively in the past, there seems to be an inherent impatience on the part of property owners and general public to get on to the bituminous surfacing stage before the traffic-bound base has fully stabilized. In several such instances it has been necessary to add extra surfacing within a year or so, or else to revert to the traffic-bound stage again and start over

Concrete, Bridge Decks: Deterioration, Coatings and Repairs

This report is not wholly a culmination of a planned or programmed research project. It is a historical account of damage sustained by both new and old concrete bridge-decks -- through freeze-thaw, salt action, etc, -- and of some expedient repairs which have been effected. The problem of durability in concrete bridge-decks has become increasingly critical during the past ten years or so and is now a major concern to highway engineers throughout the northern tier of states. While there is not yet a concerted agreement in regard to the cause of the trouble, relief is being sought through improved construction practices, air-entrainment, and protective coatings of various kinds. Similarly, relief from perpetual maintenance or complete replacement of existing bridge decks is being sought through improved methods for making repairs. The performance of individual slabs in a deck is sometimes markedly different from that of a nearby slab; and, even within a particular slab, only one corner or one end may be affected. This signifies poor concreting practices. The concrete sustaining damage was undoubtedly over-watered, over-worked, de-aired, and segregated. The proper placement of deck concrete is perhaps the more serious aspect of the problem than the repair, because improper placement automatically incurs a premature maintenance liability. Of course, as the need for repairs arises in due time, reliable methods of repair should be employed. It is in this latter respect that the repair experiences recorded in this report are expected to be the most fruitful. None of the damaged decks which have been observed thus far has shown any evidence of overloading by traffic (adjudged by the absence of any checker-board crack-pattern on the underneath side of the deck); the trouble seems to be attributable almost entirely to weathering; and the weathering invariably seeks out and attacks the poorest concrete often revealing the mistakes made by the workmen and their attempts to hide them. Improper drainage of the deck and gutter can be one of the contributing factors to damage. Even slabs and gutters sometimes have bird-baths in them. Cinders, sand, road-debris, and snow sometimes impound water and prevent drying. Such areas are exposed to water and moisture beyond their normal time and damage is often associated with these conditions

Hearing new voices: re-viewing youth justice policy through practitioners’ relationships with young people

The relationship between young people and practitioners is the centrepiece of youth justice provision, yet little research-based knowledge has accumulated on its minutiae. After reviewing reforms affecting professional discretion, the article draws on the concepts of dyadic relationships and praxis to reinvigorate a research agenda aimed at delineating a more nuanced understanding of practice relationships. Drawing on practice wisdom from across related social work fields, we argue that centralizing the practitioner-young person relationship remains the key to successful practice and thus needs greater, more detailed research attention. These claims are supported with a number of pilot interviews with youth justice workers about successful interventions that complement and extend related studies. The article concludes with suggestions for research to enable joint activity between young people and practitioners to ‘rethink’ youth justice

Some Chemical, Physical and Mineralogical Features of Soil Colloids

The -1 micron portion of several diversified soils were separated by sedimentary fractionation. Physical properties were evaluated on the -1 micron portion, the +1 micron portion, and on the original -40 sample. The -1 micron portion was analyzed for clay mineral identity by X-ray diffraction, and analyzed chemically for associated materials such as the oxides of Iron, Aluminum, Calcium, and lv!agneeium. These data present several possibilities and trends as to the inter-dependency of the involved variables, other considerations have been devoted to the geologic origin of several samples and to various physico-chemical relationships

Uncertainty Estimates for Theoretical Atomic and Molecular Data

Sources of uncertainty are reviewed for calculated atomic and molecular data that are important for plasma modeling: atomic and molecular structure and cross sections for electron-atom, electron-molecule, and heavy particle collisions. We concentrate on model uncertainties due to approximations to the fundamental many-body quantum mechanical equations and we aim to provide guidelines to estimate uncertainties as a routine part of computations of data for structure and scattering.Comment: 65 pages, 18 Figures, 3 Tables. J. Phys. D: Appl. Phys. Final accepted versio

Agreement between bovine respiratory disease scoring systems for pre-weaned dairy calves.

Clinical scoring systems have been proposed for respiratory disease diagnosis in calves, including the Wisconsin (WI) system (McGuirk in 2008) which uses five clinical signs, each partitioned into four levels of severity. Recently, we developed the California (CA) bovine respiratory disease (BRD) scoring system requiring less calf handling and consisting of six clinical signs, each classified as normal or abnormal. The objective of this study was to estimate the on-farm agreement between the WI and the CA scoring systems. A total of 100 calves were enrolled on a CA dairy and assessed for BRD case status using the two scoring systems simultaneously. The Kappa coefficient of agreement between these two systems was estimated to be 0.85, which indicated excellent agreement beyond chance. The simpler design and reduced calf handling required by the CA BRD scoring system may make it advantageous for on-farm use