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  1. Mechanical Properties and Nanostructure of Cement-Based Materials Reinforced with Carbon Nanofibers and Polyvinyl Alcohol (PVA) Microfibers

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    Description: There have been numerous studies that have aimed at improving the low tensile strength, stiffness, and toughness of cementitious materials. This study aims to show that all of these characteristics can be greatly improved by the addition of ladder scale reinforcement at the nano and micro scale. Carbon nanofibers (CNFs) as well as polyvinyl alcohol (PVA) microfibers were used as reinforcement. The mechanical properties of the nanocomposites were investigated by fracture mechanics three-point bending test. The microstructure and the morphology of nanocomposite samples were studied using an ultra high resolution scanning electron microscope (SEM). The results clearly illustrate that the incorporation of nanofibers and microfibers greatly improves the flexural strength, Young’s modulus, and toughness of the cement matrix.
    Keyword: mechanical properties, scanning electron microscopy, carbon nanofibers, hybrid composites, nanofiber reinforcement, and polyvinyl alcohol microfibers
    Creator: Surendra P. Shah, Maria S. Konsta-Gdoutos, and Zoi S. Metaxa
    Owner: Chris Diaz
    Date Uploaded: 08/14/2017
    Date Modified: 08/17/2017
    Date Created: 2011
    Rights: All rights reserved
    Resource Type: Article
  2. Crack Measurement: New Approach to Addressing Blasting Complaints

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    Keyword: vibration-induced cracking and crack response
    Creator: Charles H. Dowding
    Owner: Chris Diaz
    Date Uploaded: 08/14/2017
    Date Modified: 08/14/2017
    Date Created: 2001
    Rights: All rights reserved
    Resource Type: Article
  3. Micro-Meter Measurement of Cracks to Compare Blast and Environmental Effects

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    Description: Concern over construction vibration-induced cracking has led to development of a new approach to vibration monitoring called autonomous crack measurement (ACM) and illustrated in Figure 1. This paper describes the concept as well as sensor performance in the first test house fitted an ACM system. Response of three cracks in this concrete masonry unit (CMU) house was measured as part of the system verification. ACM employs a single sensor that measures both weather-induced micrometer changes in crack width and those produced by habitation and ground motioninduced vibration. This comparison is displayed in real time via the Internet without human interaction. Graphic display through the Internet provides a new pathway for communication with the public. Such visual comparison of changes in crack width provides a simple alternative to the present system of comparison of measured and allowable vibration time histories. Measurements reported herein show that weatherinduced response of cracks is greater than that caused by presently allowable construction-induced vibration.
    Keyword: concrete masonry unit
    Creator: Charles H. Dowding and Michael Louis
    Owner: Chris Diaz
    Date Uploaded: 08/14/2017
    Date Modified: 08/14/2017
    Date Created: 2003
    Rights: All rights reserved
    Resource Type: Article
  4. Response of Cracks to Construction Vibrations and Environmental Effects

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    Description: This paper summarizes micro-inch response of cosmetic cracks in a typical slab-ongrade ranch style house to both construction equipment-induced vibration and environmental (weather) effects. This structure was instrumented, and its response studied as part of the development of an Autonomous Crack Measurement (ACM) system. ACM systems are intended to record -- with a single sensor -- micro-inch crack displacements from both long-term environmental changes and transient construction vibrations for comparison in an understandable fashion. Ground motions were measured with velocity transducers, and micro-inch crack displacements were measured with LVDT displacement sensors. Construction within 14 m (45 ft) of the house involved trackhoe excavation for a 10x12 ft. reinforced concrete box culvert, chain trencher excavation for an 8-inch water service line, and vibratory compaction of trench backfill and granular sub-grade. As with many other studies of this nature, it was found that the weather induced crack response far exceeded that produced by construction vibrations even when produced by vibratory rolling within 3 m (10 ft ) of the structure.
    Keyword: Autonomous Crack Measurement
    Creator: Mickey L. Snider and Charles H. Dowding
    Owner: Chris Diaz
    Publisher: American Society of Civil Engineers
    Date Uploaded: 08/14/2017
    Date Modified: 08/14/2017
    Date Created: 2004
    Rights: All rights reserved
    Resource Type: Part of Book
  5. Effects of Crack Width on Carbonation Penetration: Implications for Crack-Dating

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    Description: Carbonation, a neutralizing reaction in cement paste, can be used to date cracks in cementitious materials. Currently, comparison between two cracks is the only method available to predict a relative age with carbonation. These two crack studies require a crack of known age in a similar material with similar exposure to the crack of unknown age. This thesis presents measurements of the extent of carbonation in cracks of varying width as a first step in laying a quantitative formulation for the use of carbonation in crack dating. This information will allow comparisons between two cracks of more similar exposure, but different crack width, which can expand the applicability of this dating method. Accelerated reaction rates were produced with a pure carbon dioxide environment and cement mixes with high contents of fly ash and are evaluated for economy and applicability. Relationships between carbonation penetration and crack width were established from these measurements.
    Keyword: civil engineering
    Creator: Laura E. Sullivan-Green
    Owner: Chris Diaz
    Date Uploaded: 08/14/2017
    Date Modified: 08/14/2017
    Date Created: 2005-03
    Rights: All rights reserved
    Resource Type: Masters Thesis
  6. Blast Induced Micrometer Response of Cracks in Concrete Block Structures

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    Description: Blasting and climatological response of cracks are compared for structures constructed of concrete block typical of home construction in Europe. While much has been written comparing micrometer crack response of wood frame structures typical of residential construction in North America, little has been written concerning response of structures more typical of European construction. Responses of cracks in four different structures are compared with the following locations and (wall materials): Wales, UK (Concrete Block), Florida, USA (Concrete Block – 2 cases), Wisconsin, USA (Concrete Block and Stone). Time histories of micrometer response of cracks to both blast induced dynamic effects as well as long term climatological effects are compared. These comparisons show that even for concrete block construction without wood, climatological and home heating effects have greater influence on crack response than blast induced ground motions with a wide range in intensity.
    Keyword: climatological crack and vibration
    Creator: Charles H. Dowding
    Owner: Chris Diaz
    Date Uploaded: 08/14/2017
    Date Modified: 08/14/2017
    Date Created: 2007
    Rights: All rights reserved
    Resource Type: Research Paper
  7. Internet-Enabled Geotechnical Data Exchange

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    Description: Surveillance of large geotechnical projects requires autonomous collection of data from a wide range of instrument types. An equally large range of data formats are employed by these measurement systems. A data exchange protocol is needed to make field data available for interpretation on a variety of platforms. This paper presents the results of the development of a robust Internet-enabled framework for the exchange of engineering data. Internet-enabled data exchange technology provides a standard for engineering data acquired from any combination of instruments by autonomously parsing data into a searchable database for archiving and distribution. A set of strategies and software have been deployed to create layers of abstraction that allow data files from different commercial and in-house data acquisition packages to meet standards for timekeeping, archiving, and data display. The data are stored in an Internet-accessible database and distributed to stakeholders via a password-protected Web site. The data exchange abstractions in this system allow it to be employed with an extremely wide variety of sensing techniques and data types, and the storage of data in a relational database rather than flat files provides for improved scalability in the types and volumes of data to be interpreted. These technologies have been employed in the continuous remote monitoring of a number of facilities over the past seven years.
    Keyword: infrastructure
    Creator: David E. Kosnik
    Owner: Chris Diaz
    Date Uploaded: 08/14/2017
    Date Modified: 08/14/2017
    Date Created: 2007
    Rights: All rights reserved
    Resource Type: Research Paper
  8. Comparison of Micro-inch In-Plane and Out-of-Plane Response of Cracks to Blast Vibration and Weather

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    Description: Most studies of crack response have focused on opening and closing of a crack in the plane of the wall in which the crack occurs. Crack movement also occurs perpendicular or normal to the plane of the wall. This paper will examine and compare the in-plane and out-of-plane (normal) response of cracks in two different residences near limestone quarries. In two locations, sensors that measure in-plane and normal displacement were installed side-by-side on the same crack, allowing direct comparison of the two modes of response. In a third location, a perpendicular pair of displacement sensors was installed in a corner of a room to observe the bidirectional response of the structure at a corner. Both long-term and dynamic data were recorded with the same sensors; temperature, humidity, and air over pressures were also recorded to compare blast and weather effects. Measurements show that ratios of out of plane to in plane response to dynamic events can vary. However, the ratios of out of plane (normal) response to vibratory events to that of climatological change is still as small as the ratio for in plane crack responses.
    Keyword: civil engineering
    Creator: Mike J. Waldron, Charles H. Dowding, and Jeffrey E. Meissner
    Owner: Chris Diaz
    Date Uploaded: 08/14/2017
    Date Modified: 08/14/2017
    Date Created: 2010
    Rights: All rights reserved
    Resource Type: Research Paper
  9. Response of Uncracked Drywall Joints and Panels to Blast Vibration and Weather

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    Description: Cracking is one of the most common concerns cited by owners of structures adjacent to construction or mining blasting. While a large database of case studies documenting the relative insignificance of ground motion induced by responsible blasting compared to weather effects on cracks in nearby structures has been established, the perception of damage to structures, particularly residences, remains common. In allegations of blast damage, litigants may downplay the utility of the database of crack response to weather and ground motion, citing that the behavior of the structure is somehow drastically altered by the existence of cosmetic cracks. In response, this study will compare the response of cracked and uncracked areas of gypsum board in two structures – one near a surface coal mine in Indiana, the other near a limestone quarry in Florida – to blast-induced ground motion and air over-pressure as well as changes in temperature and humidity.
    Keyword: Autonomous Crack Measurement
    Creator: Charles H. Dowding and Jeffrey E. Meissner
    Owner: Chris Diaz
    Date Uploaded: 08/14/2017
    Date Modified: 08/14/2017
    Date Created: 2011
    Rights: All rights reserved
    Resource Type: Research Paper