Impacts of Openness

This is the recording from the Impacts of Openness lightning talk session that was held on Friday, October 25, 2013, from 10:00 a.m. - noon in Watson Library, room 455 during the KU Libraries' celebration of Open Access Week.This event brings together several speakers from a variety of fields, each of whom will give a 10-minute presentation about the impact of openness in their work. More information about this event is available at http://openaccess.ku.edu/impacts-openness-lightning-talks-october-25

A Generalized Investigation of Selected Highway Design and Construction Factors by Regional Geomorphic Units within the Continental United States

Abstract not availabl

Nationwide evaluation study of asphalt concrete overlays placed on fractured PCC pavements

Historically, agencies responsible for pavement rehabilitation have tried a wide variety of materials, processes, and construction methods to eliminate or minimize reflective cracking of asphaltic concrete overlays placed on existing portland cement concrete (PCC) pavements. Over the last 10 years, the fractured slab approach using rubblize, crack and seat, and break and seat has gained increased acceptance. Because the fractured slab approach has gradually evolved through field demonstration and actual projects, very little fundamental knowledge concerning design, construction, and performance models is available. Understandably, performance to date has been variable. To improve the state of the art and develop a better understanding of these techniques, a nationwide study was undertaken. A literature review resulted in the location of nearly 500 highway projects throughout the United States. From this generalized data base, approximately 100 sites were selected for detailed field studies. Field crews conducted visual distress surveys to assess pavement performance and nondestructive deflection testing to assess the in situ characteristics of the pavement layers. The general approach used for the research study and the analysis of field performance and structural data obtained is presented. Performance predictive equations are presented along with the evaluation of the backcalculated effective moduli of fractured PCC slabs for each technique. Analysis of within and between project variability is presented. The selection of optimal rehabilitation procedures and strategies for deteriorating highway pavements requires a knowledge of the type and cause of the distress, determination of candidate rehabilitation procedures, and selection of an optimal strategy based on economic and other considerations. For portland cement concrete (PCC) pavements, the array of possible rehabilitation procedures includes nonoverlay methods such as undersealing, grinding of the surface, and removal and replacement of distressed areas; fulf reconstruction by replacement or recycling; PCC overlays; and asphaltic concrete (AC) overlays. Review of current practice indicates that AC overlays are the most commonly used PCC rehabilitation procedure, with about $1 billion of AC overlays placed· each year, and this amount will likely increase in the future (J). Even though they are commonly used, the performance of AC overlays on PCC pavements is often hampered by the occurrence of reflection cracks over existing joints and cracks. Reflection cracks in the AC overlays are caused by a combination of thermal and traffic-induced stresses. Expansion and contraction of the PCC pavement results in horizontal movements that produce strains in the AC overlay exceeding its tensile strength. Traffic loads can cause vertical differential movements at the location of joints and working cracks in the PCC slab and induce critical shear stresses at the bottom of the AC layer. The overlay immediately over the joints and working cracks in the PCC is not able to accommodate these localized movements, resulting in the development of reflection cracks. A wide variety of rehabilitation techniques aimed at preventing the formation of, or minimizing, reflection cracking have been attempted. They include thick (conventional) overlays, crack relief layers, the saw and seal technique, special overlay and interface materials, and the fractured slab approach. Of these, the technique that has been used increasingly over the last 10 years has been the fractured slab approach. The major objective of the fractured slab approach is to reduce the effective in situ slab length before the overlay is placed. If this is effectively accomplished, the likelihood of having reflective cracks appear is significantly reduced or eliminated. The probability of reflective cracking is proportional to the horizontal movement at joints and cracks, which in tum is directly proportional to the spacing between joints and cracks. The fractured slab category is generally subdivided into three major types of rehabilitation: rubblize, crack and seat, and break and seat. Rubblize is a fractured slab process intended to transform the existing PCC layers into fragments having textural and gradational characteristics similar to those of a large aggregate size crushed stone base. It is most effectively accomplished with a resonant pavement breaker, which has been successfully used on all types of existing PCC pavements [i.e., jointed plain (JPC), jointed reinforced (JRC), and continuously reinforced (CRC) concrete pavements]. Crack/seat and break/seat are fracture techniques intended to produce very short rigid slabs whose effective lengths vary from 12 to 48 in. The techniques are similar, with guillotines or spring-arm (whip) hammers being used to develop reduced crack spacings in the existing PCC pavement. There is, however, a significant distinction between the two techniques. Crack/seat is associated with the fractured slab process conducted solely on JPC pavements. For these pavements, th