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Alkali-Silica Reaction (ASR) in Slab-on-Grade Driveways

CA performed a forensic engineering investigation to determine the cause(s) of the distress observed in the exterior concrete slab-on-grade driveways and sidewalks of numerous homes in a single family residential neighborhood. The observed distress consisted of surface discoloration, pop outs, and peeling of the membrane coating, which was installed on several driveways in an attempt to remediate the distress. CA’s forensic investigation included, among others, visual inspections of more than 100 installations, concrete core sampling, and testing of the bond strength between the membrane coating and the concrete substrate. In addition, CA directed petrographic examination of several concrete cores sampled from the distressed and non-distressed locations in order to investigate any alkali aggregate reaction in the concrete. CA determined that alkali-silica reaction in the concrete was one of the cause(s) of the observed distress and developed recommendations for the concrete surface repair and remediation of the in-place concrete pavement.

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Evaluation of a Shopping Center Flooring System

An expansion to the second story of a commercial retail shopping center consisted of the addition of an elevated slab supported by several different types of framing systems, including a post-tensioned concrete beam and pan joist system, a composite flooring system consisting of metal decking and reinforced concrete, and a reinforced concrete slab and beam system. The flooring system of the second floor expansion contained limestone tile as the final floor finish, which exhibited signs of isolated distress in the form of random map cracking. CA performed, among other things, a detailed condition survey of the flooring system and its distress, a review of drawings and plans, an examination of the materials utilized in the flooring system, and a structural evaluation of the flooring system and its individual components. Testing conducted during the site investigations included bond pull-off tests, ground penetrating radar (GPR) mapping, concrete core sampling, and elevation surveys.  CA determined the cause of the distress exhibited by the tile flooring, provided recommendations for the repair and remediation of the flooring system, and developed guidelines to reduce the progression of the distress.

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Concrete Strength Analysis of a Rural Bridge Deck

The project consisted of the rehabilitation of a 165 ft. long rural steel girder bridge. The concrete bridge deck was to be replaced with a cast-in-place, high performance concrete deck to be supported by the existing steel beams. During the final days of construction, CA was retained to determine the cause of the low concrete strength test results and slow early-age concrete strength gain. CA’s forensic engineering investigation included the review of quality control strength test results and concrete production data, extraction and testing of concrete core samples, a petrographic examination, and a general assessment of the concrete surface quality. CA’s investigation contributed to opening the bridge to traffic only several days after the investigation was completed.

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Investigation into the Cause of Cracking in Precast Post-Tensioned Concrete Beams

The construction of Highway 10 in Puerto Rico has been one of the largest and longest highway projects in the island. This highway runs through Puerto Rico’s scenic mountains and was expected to be completed in 2015. Cracking in the precast, post-tensioned concrete beams manufactured on-site resulted in concerns to the public authorities requiring immediate action. CA provided construction consulting services during construction of various post-tensioned concrete beams and sections of Highway 10. CA inspected many of the beams where cracking was observed, visited the concrete production facilities on-site, observed casting operations, and evaluated field data including, but not limited to, internal concrete temperatures of the concrete beams. In addition, CA’s investigation included a review of concrete mixture proportions, material information, concrete quality control testing results, curing, and demolding practices to determine the causes of the concrete cracking observed and propose remediation procedures.

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Precast Concrete Welded Connections

A six (6) story parking garage for a residential building consisted of precast, pre-topped double-tee beams and pre-cast wall panels. A concern regarding life safety was expressed due to the observed distress consisting of spalling of the concrete beneath the welded connections along the flange of adjacent double-tee beams. In addition, concrete cracking in the vertical panels of the pre-cast walls was observed. CA’s investigation focused on determining the cause of the distress and included, but was not limited to, a detailed condition survey and visual inspections of over 1,600 welded connections and a review of the construction drawings and plans. CA determined the cause of the observed distress and developed recommendations for repair and rehabilitation of the concrete structure, including design of repair procedures, materials selection, and quality control/assurance procedures during and after implementation of the repairs.

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Power Plant Scrubber Mass Concrete Foundation

The project consisted of a cast-in-place reinforced mass concrete foundation at a power plant in Texas. The foundation was 94.5 ft. in diameter, nine (9) ft. thick, contained two (2) mats of reinforcing steel consisting of four (4) layers of large diameter (No. 11) bars, approximately 2,600 cubic yards of concrete, and was supported by 339 piles for the addition of a 525 ft. tall reinforced concrete chimney. The structural integrity and capacity of the foundation was questioned due to owner observed construction defects during concrete placement. CA’s investigation included, among others, review of structural concrete design calculations, a finite element structural analysis model to evaluate internal stresses, non-destructive testing of concrete, core sampling, assessment of the concrete production methods and logistics, and  numerous site visits to conduct field investigations and condition assessments totaling over 1,400 man-hours. CA’s extensive investigation uncovered the cause(s) of the distress and structural deficiencies.

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Industrial Parking Lot Concrete Pavement Design

The project consisted of the rehabilitation of two concrete pavement parking lots in an industrial park in Laredo, Texas, including the removal and replacement of distressed areas as well as repairs at the expansion joints in concrete slabs. CA performed a detailed condition assessment of both parking lots to observe the distress and developed repair recommendations pertaining to concrete properties, concrete pavement thickness design, expansion joint transfer details, expansion joint sealant, drainage, preparation, material, and base and subgrade preparation.

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Indoor Concrete Topping Placement Recommendations

Construction at a university recreation and wellness center required a concrete topping slab in the main entrance and lobby areas. CA provided structural engineering consulting services including, but not limited to, improvements to the concrete placement activities and incorporation of necessary measures to reduce the potential for drying shrinkage cracking. CA’s experience with concrete toppings and understanding of concrete placement fundamentals contributed to successfully addressing the project’s needs and its unique conditions. CA provided recommendations for the concrete placement including reducing structural restraint and bond, implementing drying shrinkage cracking control and appropriate curing methods, and using proper joint design and layout.

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High School Cast-in-Place Concrete Crack Investigation

A high school in Bellaire, TX consisted of a cast-in-place, reinforced concrete, slab-on-ground with intermediate grade beams and drilled piers. CA was retained to investigate distress that included cracking in the floors and walls in several buildings of the high school. CA performed, among others, a general condition survey, photographic and schematic documentation, and a relative elevation survey of the floor. CA also evaluated original plans, drawings, and project specifications for comparison with the as-built structure. The quality of concrete was also examined to determine the presence of any construction defects or deficiencies in the concreting operations.

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Structural Engineering Consulting: Expressway Concrete Bridge

The project involved converting a section of a concrete pavement highway in Puerto Rico with two lanes of traffic in each direction into an expressway concrete bridge requiring three lanes in each direction. CA’s structural engineering consulting services included evaluating the structural adequacy of the as-built cast-in-place concrete bridge foundations to resist the design loading conditions. CA performed a detailed structural analysis of the bridge foundations using both traditional beam theory and strut-and-tie modeling.  CA conducted an investigation that included, among other things, a review and interpretation of specifications, plans and construction drawings, concrete cylinder and core strength test reports, and applicable industry standards. Further, CA developed recommendations to improve the durability of the concrete foundation and to ensure the service life of the bridge structure in service.