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Concrete Materials Consulting for San Juan’s Rapid Urban Train System

This $1.7 billion, 17.3 km mass transit system aimed to alleviate the traffic congestion in San Juan, the most densely populated city in Puerto Rico. It included both underground and elevated rail sections and multiple stations. Tunneling was performed below the water table near the ocean in a Zone IV seismic area. Some of the major challenges involved the casting of massive concrete sections underground as well as the design of precast concrete tunnel sections with special concrete mixtures, all of which were attained with innovative use of admixtures and supplementary cementitious materials as well as optimized concrete production techniques. CA provided consulting services regarding the conformance with specifications, concrete mixture proportions, concrete production, placement of concrete, curing techniques, concrete durability, quality control, and quality assurance during construction. In addition, the structural strengthening of the columns supporting the elevated sections of the rail to meet seismic Category IV design criteria in portions of the structure already built posed a major challenge, which was addressed with novel and innovative methodologies including, but not limited to, fiber reinforced polymer wrapping.

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Corrosion of Steel Chimney

The owners of a steel smokestack expressed concerns over the amount of steel corrosion and resulting loss of cross sectional area as well as concerns over the large amount of cracking in the smokestack’s cast-in-place concrete foundation. CA investigated the structural integrity of the concrete foundation and smokestack and provided recommendations for their repair and remediation. CA performed an assessment of the condition of the concrete foundation and smokestack including site inspection, non-destructive testing services such as ground penetrating radar scanning and ultrasonic thickness scanning, concrete coring, petrographic examination, and structural analysis and design. CA’s investigation determined that the smokestack had lost close to 40% of its cross section in certain areas. Based on the investigation, CA developed recommendations for restoring the structural integrity of the smokestack by remediating the wall thickness in several areas and repairing the concrete cracking.

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Litigation Support for Masonry Brick Screenwalls

This project consisted of conducting an investigation into the cause(s) of the observed deterioration of brick perimeter screenwalls in North Texas. The brick masonry units were imported into the United States. Distress observed included cracking, crumbling, deterioration, fading color, and warping. Among the areas investigated were the manufacturing processes, quality control, and adequacy of the specification requirements for the masonry units for their intended purpose. Findings from testing performed indicated that the masonry units did not meet the requirements for durability in a North Texas environment. Among other causes, the firing process during manufacturing most likely affected the durability and performance of the brick in service. CA served as an expert witness, indicating that lack of understanding, confusion, and relaxed implementation of the industry standards for materials in the masonry structures contributed to problems in certifying the quality of the bricks.

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Construction Consulting for the San Roque Dam and Reservoir

Located in the Island of Luzon on the Agno River, approximately 200 km from Manila in the Philippines, this dam and reservoir project intended to produce non-polluting, hydroelectric power, provide water irrigation, reduce downstream flooding, and improve water quality in the San Roque River. The project included a 200-meter-high rock fill dam to be the twelfth highest embankment dam in the world. CA provided construction troubleshooting services and recommendations for concrete mixture proportions, concrete production, and concrete placement and finishing for the casting of mass concrete sections utilizing high performance concrete for the concrete spillway and tunnel sections. Among the challenges being faced was the production of concrete to be placed on very steep slopes and long tunnel sections while achieving a smooth finish with reduced cracking to resist the forces of high water flows. CA was also involved in developing repair recommendations for the rehabilitation of some of the concrete already in place.

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Forensic Pavement Analysis of a Parking Lot

The forensic investigation for this project consisted of sampling, testing, and evaluating the pavement structure including base, sub-base, and natural soil materials, and determining the cause(s) of the observed distress of the parking lot at the Redstone Golf Course in Humble, Texas. Distress in the parking lot was mainly in the form of cracking with isolated heaving and bulging at several locations. CA performed a detailed condition assessment including coring and excavations to sample, document, and evaluate the pavement system. Destructive testing included petrographic examination and chemical and mineralogical analysis of the different materials comprising the pavement system, natural soil, stabilized subgrade, and selected materials. Further, CA’s forensic investigation included, among other things, evaluating the construction practices, quality control testing, and the overall drainage and landscaping design for the site.

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Forensic Engineering Investigation of Precast / Prestressed Railroad Ties

CA conducted an extensive forensic engineering investigation into the cause of premature distress of thousands of precast/prestressed concrete railroad ties in service along numerous railroad lines primarily in the northern part of the United States. The forensic investigation included performing a comprehensive condition survey to characterize and assess the extent of the distress, sampling and testing to determine the internal distress mechanism causing the early deterioration of the railroad ties, and identifying the factors affecting the progress of the distress mechanism. The investigation included a detailed review and evaluation of the concrete production, materials, mixture proportions, quality control and curing practices, effect of the distress on the structural adequacy of the ties, distress documentation, non-destructive evaluation, mineralogical and chemical analysis of alkali aggregate reaction, and petrographic examination, among others. This investigation included several potential distress mechanisms including delayed ettringite formation (DEF), alkali-silica reaction (ASR), and freeze-thaw damage.

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Repair and Rehabilitation of a Post-Tensioned Parking Garage

A two story, cast-in-place post-tensioned concrete parking garage cut into the side of a slope provided a parking area and structural support for a major grocery store. The second floor of the parking garage was level with the surface parking area adjacent to and in front of the grocery store. Issues investigated were related to water intrusion, concrete cracking, foundation performance, retaining wing wall movement, loss of subgrade support, jointing, construction defects, moisture management, and performance of the post-tensioned beams.  These issues were investigated to determine any possible impacts on the long-term performance of the structure. CA performed, among other things, a detailed condition assessment of the structure, review of construction related documents, drawings, and plans, and a structural analysis and evaluation of the post-tensioned structure. CA successfully determined the causes of the concerns and developed recommendations for repair and rehabilitation of the structure to restore its performance.

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Lock and Dam Concrete Mix Design

The Montgomery Point Lock and Dam project consisted of a lock and dam in the lower White River which is part of the McClellan – Kerr Arkansas River Navigation System. In 1995, the design team of this Corps of Engineers lock and dam project was awarded “Project of the Year” by the local chapter of the American Society of Civil Engineers. CA provided consulting engineering services regarding constructability issues, troubleshooting concrete related problems, and the evaluation and optimization of the mass concrete mix design, materials selection, and construction procedures. The mass concrete mix proportioning and placement was attained through the innovative use of supplementary cementitious materials and optimization of the concrete production techniques.

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Use of Supplementary Cementitious Materials at the McMurtry Building

This project involved consultation for the production of sustainable, architectural, white concrete for the construction of the McMurtry Building at Rice University in Houston, Texas. The many challenges associated with the architectural and structural concrete included the use of seventy percent cement replacement with slag as a supplementary cementitious material while achieving adequate strength gain during early ages to meet the demands of the construction activities. CA developed recommendations on the selection of the concrete materials and the concrete mixture proportions, guidelines for the batching and mixing of the concrete, formwork details, form release agents, and concrete consolidation procedures. The final selection was based on the casting of several mockups. Other issues addressed included recommendations for the protection of the architectural concrete during other construction activities such as acid wash of the CMU installations.

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Mass Concrete Foundation Placement and Monitoring Plan

The project consisted of the construction of a 13,000 cubic yard mass concrete mat foundation for a 46-story office building pre-certified as LEED Silver. CA’s work included working with the assistant project manager and Engineer of Record to develop a construction plan for the placement, curing, and early age protection of the concrete to ensure the quality of the concrete in-place. CA developed a plan for the preparation and placement of the mass concrete including monitoring of internal concrete temperatures in order to prevent distress due to thermal effects and drying shrinkage. The work also included, among other things, the review of plans, drawings, specifications, and evaluation of the mixture proportions. CA’s work also included developing the quality control program for acceptance of the fresh concrete delivered to the job, temperature monitoring plan, concrete specifications, curing methods, and early age protection to prevent distress of the concrete. CA was able to provide the General Contractor with guidelines for proceeding efficiently with construction of the concrete foundation while following prudent mass concreting practices.