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Triandafilou L.N.,Office of Infrastructure Research and Development
Public Roads | Year: 2011

Researchers and practitioners are applying fiber reinforced polymer composites and reinforced thermoplastics in construction and rehabilitation of highway structures. Transportation agencies face ever-increasing challenges minimizing congestion and ensuring the safety of travelers and highway workers while undertaking necessary construction projects. The goal is to offer motorists high-quality, longer lasting highways and bridges while reducing the construction time and traffic congestion that cost the Nation billions of dollars each year in wasted time and fuel. FRP is a general term for polymer-matrix composites reinforced with cloth, matting, strands, or other fibers. FRP composites consist of thermoset resins, which once cured, cannot be returned to an uncured state. Erecting bridges in environmentally sensitive areas presents a number of challenges, not the least of which is getting the requisite heavy machinery into the area. The self-consolidating concrete mix design uses high-range water reducers to achieve enhanced flowability and viscosity-modifying admixtures to achieve stability, eliminating aggregate segregation.

Briaud J.L.,Texas A&M University | Koohi Y.,Fugro | Nicks J.,Office of Infrastructure Research and Development | Jung I.,Texas A&M University
Journal of Geotechnical and Geoenvironmental Engineering | Year: 2015

The San Jacinto Monument was built in 1936 to celebrate the 100 year anniversary of the battlefield victory that gave Texas its freedom. Ray Dawson was in charge of the foundation design and decided to instrument the foundation to monitor the settlement of the Monument. The settlement has been recorded since 1936 and provides a very valuable long-term record. This settlement and other geotechnical data were studied and reported by Briaud and his co-authors in 2007. That study was based on data available at the time, which was primarily from a 61-m-deep boring in 1953. In 2007, Fugro and Texas A&M University drilled a new boring with sampling to a depth of 78 m, conducted in situ tests to 36 m, and laboratory tests on the samples recovered. Updated settlement calculations are provided using this new data; they show reasonably good agreement with modern settlement techniques. One of the issues possibly affecting the settlement readings is the subsidence of the ground surface, which can reach 3 m in that area of Houston. A second part of this article presents calculations and numerical simulations to evaluate the influence of subsidence on the recorded settlement of the Monument. It is shown that the true settlement of the SJM is 295 mm while the measured settlement is 328 mm. The reduction is due to the different influence of the subsidence on the settlement of the shallow benchmark and of the Monument. © 2015 American Society of Civil Engineers.

O'Reilly M.,University of Kansas | Darwin D.,University of Kansas | Browning J.,University of Kansas | Xing L.,Archer Daniels Midland Company | And 2 more authors.
ACI Materials Journal | Year: 2013

Three commercially available corrosion inhibitors-calcium nitrite, a solution of amines and esters, and an alkenyl-substituted succinic acid salt-are evaluated in conjunction with conventional reinforcement in concrete based on corrosion rate, metal loss, the critical chloride corrosion threshold (CCCT), pore solution analyses, and concrete compressive strength. All three inhibitors increase time to corrosion initiation and decrease corrosion rate, but are less effective in cracked concrete than in uncracked concrete. Of the three inhibitors, the alkenyl-substituted succinic acid salt results in the greatest decrease in corrosion rate, but exhibits the lowest CCCT-below that measured in concrete with no inhibitor. The compressive strengths of concretes containing the amine-ester inhibitor and the alkenyl-substituted succinic acid salt were 15% and 60% lower, respectively, than concrete without an inhibitor. For the latter inhibitor, pore solution analyses indicated elevated sulfate contents at 1 and 7 days, which may explain the low CCCT and strength. Paste containing the amine-ester inhibitor had an elevated sulfate content at 7 days. © Copyright 2013, American Concrete Institute. All rights reserved.

Darwin D.,University of Kansas | O'Reilly M.,University of Kansas | Browning J.,University of Kansas | Locke C.E.,University of Kansas | And 6 more authors.
Journal of Materials in Civil Engineering | Year: 2014

Techniques for making epoxy-coated reinforcement more corrosion resistant, including epoxies with increased adhesion to the steel; concrete with a decreased water cement ratio; concrete containing calcium nitrite or one of two organic corrosion inhibitors; bars with a primer coating containing microencapsulated calcium nitrite applied prior to epoxy application; and bars coated with zinc prior to epoxy application are compared based on the chloride content required to initiate corrosion and corrosion losses using the southern exposure and cracked beam tests. The coatings on all bars are penetrated prior to testing to simulate damage in the field. The results indicate that, even when damaged, conventional epoxy coatings result in much higher concrete chloride contents at corrosion initiation and much lower corrosion losses than exhibited by conventional reinforcement. A reduced water-cement ratio, corrosion inhibitors, and the primer coating containing microencapsulated calcium nitrite provide protection in uncracked but less or no protection in cracked concrete. The bars coated with zinc prior to epoxy application exhibit relatively high corrosion rates because of preferential losses to the zinc, and no improvement in corrosion performance is observed for epoxies with increased adhesion. © 2014 American Society of Civil Engineers.

Munoz J.F.,University of Wisconsin - Madison | Meininger R.C.,Office of Infrastructure Research and Development | Youtcheff J.,Office of Infrastructure Research and Development
Transportation Research Record | Year: 2010

Aggregates are often considered as inexpensive inert filler material in concrete. However, the mixture of the aggregate with the cement paste creates one of the most vulnerable areas of concrete, the interface of aggregate and cement paste. The judicious application of nanoporous thin films (NPTFs) on the aggregate's surface is an effective way to improve those interfaces. The most recent work on concrete shows that the use of different types of NPTF can induce changes in different properties of concrete or in an aggregate's mineralogy. In particular, the observed changes in mechanical properties such as compressive, flexural, and tensile strengths; modulus of elasticity; and drying shrinkage can ameliorate longitudinal and transverse cracking, corner breaks, punchouts, and D-cracking. Several mechanisms are proposed to explain the changes observed in concrete and the implications for its ultimate performance. These new results open doors for new applications of NPTFs and indicate possible future research in this field.

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