Cracking of newly placed binary Portland cement-slag concrete adjacent to bridge deck expansion dam replacements has been observed on several newly rehabilitated sections of bridge decks. This paper investigates the causes of cracking by assessing the concrete mixtures specified for bridge deck rehabilitation projects, as well as reviewing the structural design of decks and the construction and curing methods implemented by the contractors. The work consists of (1) a comprehensive literature review of the causes of cracking on bridge decks, (2) a review of previous bridge deck rehabilitation projects that experienced early-age cracking along with construction observations of active deck rehabilitation projects, and (3) an experimental evaluation of the two most commonly used bridge deck concrete mixtures. Based on the literature review, the causes of concrete bridge deck cracking can be classified into three categories: concrete material properties, construction practices, and structural design factors. The most likely causes of the observed early-age cracking were found to be inadequate curing and failure to properly eliminate the risk of plastic shrinkage cracking. These results underscore the significance of proper moist curing methods for concrete bridge decks, including repair sections. This document also provides a blueprint for future researchers to investigate early-age cracking of concrete structures.
The main objective of this research is to identify the causes of longitudinal early age cracking in concrete deck segments placed adjacent to the newly replaced bridge deck expansion joints. This study satisfies this objective via a three-part investigation into the cracking propensity of concrete repairs on bridge decks placed in the recent decade through a case study involving bridge decks in Pennsylvania. These three parts consist of (1) a comprehensive literature review, (2) a review of past bridge deck rehabilitation projects that experienced early age cracking and construction inspection of active bridge dam rehabilitation projects, and (3) an experimental evaluation of the fresh and hardened properties of concrete in the laboratory to quantify the risk of cracking of the two most commonly used concrete mixtures for bridge deck construction and rehabilitation. This three-part investigation can then be utilized by other researchers to investigate early age cracking occurrences on bridges under their purview.
This section provides the information obtained from site visits to 11 past bridge deck expansion dam rehabilitation projects and 2 active deck dam rehabilitation projects in Pennsylvania. The variables considered by the research team during these site visits include the following:(1)concrete mixture proportions and material properties: w/cm, cementitious materials content, cement type, aggregate type and content, mineral and chemical admixtures, plastic air content, slump (design and measured at site), and 28-day compressive strength (structural design, minimum required by job specifications, and laboratory test results);(2)construction and curing practices: removal of old dam and adjacent concrete, cleaning and preparing the repair area, cleaning and epoxy coating of existing rebar within the repair area, installing new dam and additional rebar, placement, compacting and finishing concrete, ambient air temperature, relative humidity and wind speed, concrete temperature at placement, curing methods, and duration;(3)structural design factors: reinforcing bar size and spacing and cover thickness.
The tests performed on the concrete mixtures were separated into three categories: (1) fresh properties (slump test: ASTM C143-05a and plastic air content: ASTM C231-10), (2) mechanical properties (indirect tensile strength: ASTM C 496-11, uniaxial compressive strength: ASTM C 39-05, and elastic modulus: ASTM C469-10), and (3) shrinkage and temperature properties (drying shrinkage: ASTM C157-08, restrained ring shrinkage: ASTM C1581-09, heat of hydration: ASTM C1064-08, and coefficient of thermal expansion: ASTM C531-00). Since the w/cm was greater than 0.42, autogenous shrinkage was deemed negligible (60). A description of the experiments along with the results and discussion is provided below.
The main objective of this research was to identify the causes of longitudinal early age cracking in concrete deck segments placed adjacent to the newly replaced bridge deck expansion joints and to provide a blueprint of steps necessary to perform this type of investigation. The steps consisted of (1) a literature review of the causes of early age cracking on bridge decks, (2) a review of past and active bridge deck rehabilitation projects, and (3) an experimental evaluation of the two most commonly used bridge deck concrete mixtures.
Overall, an integrated approach, to ensure proper selection and design of concrete materials, proper structural design of the deck (including the repair section), and proper construction and curing methods, is needed to minimize early age cracking of concrete deck and repair sections. Construction specifications and quality assurance practices must be updated as needed to benefit from the available knowledge in the literature to prevent early age cracking. Further research is needed to quantify the effect of cracks on the durability and service-life expectancy of bridge decks and to identify the best remediation techniques and the optimum time to repair the existing cracked bridge decks.
Expansion Microscopy (ExM) is a novel tool improving the resolution of fluorescence microscopy by linking the sample into a hydrogel that gets physically expanded in water. Previously, we have used ExM to visualize the intracellular Gram-negative pathogens Chlamydia trachomatis, Simkania negevensis, and Neisseria gonorrhoeae. Gram-positive bacteria have a rigid and thick cell wall that impedes classic expansion strategies. Here we developed an approach, which included a series of enzymatic treatments resulting in isotropic 4× expansion of the Gram-positive pathogen Staphylococcus aureus. We further demonstrate the suitability of the technique for imaging of planktonic bacteria as well as endocytosed, intracellular bacteria at a spatial resolution of approximately 60 nm with conventional confocal laser scanning microscopy.
SET-XP is an epoxy-based high-strength anchoring adhesive. SET-XP is a 1:1 ratio, two-component anchoring adhesive for anchoring and doweling into concrete (cracked and uncracked) and masonry (uncracked) applications.
Anchoring adhesive shall be a two-component high-solids, epoxy-based system supplied in manufacturer's standard cartridge and dispensed through a static mixing nozzle supplied by the manufacturer. The adhesive anchor shall have been tested and qualified for performance in cracked and uncracked concrete per ICC-ES AC308. Adhesive shall be SET-XP adhesive from Simpson Strong-Tie, Pleasanton, CA. Anchors shall be installed per Simpson Strong-Tie instructions for SET-XP epoxy adhesive.
For ETAG 001 Annex C and EOTA TR029 design methodologies: Titen HD® Heavy-Duty screw anchor Throughbolt WA torque controlled expansion anchor BoAX-II torque controlled expansion anchor BoAX-FMC torque controlled expansion anchor VT-HP adhesive with threaded rod and rebar SET-XP adhesive with threaded rod and rebar AT-HP/AT-HP PLUS adhesive with threaded rod and rebar POLY-GPG/POLY-GPG PLUS adhesive with threaded rod and rebar POLY-GPG Winter adhesive with threaded rod and rebar Vinylester adhesive anchor
Like most of the Justices, Roberts was uneasy with the law's expansion of Medicaid. He felt that the continuance of pre-existing Medicaid funding could not be conditioned on states complying with its expansion. If states were able to opt out while retaining the funding, Roberts thought that this section of the ACA could be sustained.
University of Arizona professor Michael Brian Schiffer, PhD, says, "Sony was not first, but its transistor radio was the most successful. The TR-63 of 1957 cracked open the U.S. market and launched the new industry of consumer microelectronics." By the mid-1950s, American teens had begun buying portable transistor radios in huge numbers, helping to propel the fledgling industry from an estimated 100,000 units in 1955 to 5,000,000 units by the end of 1968. As a result of the popularity of transistor radios, which empowered privacy and individualism, the way people listen to radio or music has changed forever. Sony also launched the world's first integrated circuit radio, the ICR-100 in 1967.
Sony played a major role in the development of Japan as a powerful exporter during the late 20th century. From the late 80s to early 2000s, it aggressively expanded into a variety of businesses, from film (Sony Pictures Entertainment) and insurance (Sony Life) to banking (Sony Bank) to internet service providing (So-net) and gaming (Sony Interactive Entertainment). It also beefed up the music business it had operated in Japan, CBS/Sony Record, and turned it into Sony Music Entertainment, a multinational music label group. Part of its motivation for expansion was the pursuit of "convergence," linking film, music, and digital electronics via the Internet. However this strategy ultimately failed, merely damaging Sony's balance sheet and making the company's business structure highly complex.
Abstract:In this study, a field survey was conducted on the fixed anchorages of the operation and power generation facilities installed in domestic power plants. A static/dynamic performance evaluation was conducted to present safety evaluation guidelines that meet the domestic seismic performance requirements. Seismic performance tests were performed on the post-installed set anchors M10 and M12, which are mainly used for anchorages in accordance with the US and European seismic performance standards. The dynamic shear test results showed that the M12 anchor met the seismic performance verification criterion, whereas the M10 anchor did not because its dynamic performance was reduced, owing to the cyclic loading. In the results of the dynamic pull-out test, M12 also met the seismic performance verification criterion, whereas M10 was safe only in a non-cracked state. In summary, the seismic performance of M12 in both cracks and non-cracks was satisfied, but, in the case of M10, the results were not satisfied in cracks. This was an experimental study; it will be necessary to conduct additional analytical research in the future to verify the reliability and parameters of the experiment.Keywords: post-installed anchor; structural performance evaluation; dynamic load protocol; shear; pull-out; cracked concrete; seismic 2b1af7f3a8