NDT Services at a Distribution Center Concrete Pavement Parking Lot

CA conducted an investigation to determine the cause(s) of the distress in the exterior concrete pavement at a distribution center facility in Houston, Texas. The investigation consisted of a comprehensive assessment of the structural integrity of the pavement using destructive and non-destructive testing evaluation techniques as well as the excavation of pits for geotechnical exploration and testing in order to evaluate the as-built soil stabilization methods. Non-destructive testing services provided on this project included ground penetrating radar scanning and relative elevation surveying. Other activities included the evaluation of the original concrete pavement design and assumptions, performance of a life cycle analysis, performance of service life calculations given the actual usage of the pavement, and review of construction related issues. CA also developed recommendations for the repair and remediation of the concrete pavement system.

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.

Construction Defects at a Multifamily Residential Building

CA performed a forensic engineering investigation of 15 buildings in a multifamily residential complex to investigate alleged construction defects. Among the many concerns investigated were the construction of the roofs, exterior walls, floors, building envelope related problems, air quality issues including moisture penetration and mold growth, and water induced deterioration of building materials. The overall investigation included, among other things, performing a survey to assess the existing condition of the structures, water testing at selected locations in the envelope of the buildings including exterior walls and balconies, testing of the HVAC systems, air quality testing for mold, material sampling, and moisture content determinations of building exterior areas.

Structural Evaluation and Testing of a Parking Structure

Work performed on a parking structure located in Plano, Texas, encompassed a two phase investigation. Phase I consisted of investigating the cause of cracking occurring in the precast, prestressed double tee beams which resulted in the repair or replacement of several double tees. The forensic structural engineering investigation included a condition assessment of the parking garage structure, evaluation of the double tees removed from the structure, sampling of the concrete, non-destructive testing, petrographic examination, and analytical testing. Phase II consisted of investigating the cause of distress in the architectural precast concrete elements by performing a condition assessment and evaluation of the architectural precast elements in-place. It involved determining the adequacy of the erection details, connections, and the overall structural integrity of the precast architectural members.  CA’s forensic consulting work on this project involved performing a structural analysis, sampling, testing, and petrographic examination of the concrete, the review of concrete production and construction practices, and the development of recommendations for rehabilitation and maintenance of the parking garage structure.

Heat Flow Analysis of Mass Concrete

CA has conducted heat flow analyses of mass concrete structures. These have included evaluating the effect of the concrete placement sequence, structural specifications, ambient conditions, and concrete materials and their mix proportions on the cumulative heat generation and internal temperature of the mass concrete construction and thus, on the quality of the in-place concrete. The heat flow analysis and the predicted temperature profiles were later confirmed by field measurements during actual construction. The information developed by CA was instrumental in determining the concrete curing, early age protection, and form removal practices followed by the contractor in the job. CA has also investigated the cause(s) of cracking as a result of thermal induced stresses in other facilities such as mass concrete foundations and precast/prestressed concrete highway structures.

Quality Control of Mass Concrete: UT MDA Mat Foundation

The project consisted of the construction of a 22,000 cubic yard mass concrete mat foundation for a medical facility in Houston, TX. CA’s work consisted of working with the Structural Engineer of Record, General Contractor, Concrete Sub-Contractor, Independent Testing Laboratory, and the Ready-Mixed Concrete Supplier to develop a construction plan for the placement, curing, and 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.  This plan was based upon several meetings with all parties involved in the construction, review of plans, drawings, and specifications, evaluation of the concrete mixture proportions, and prior experience with mass concrete. CA’s work also included developing the quality control program for accepting the fresh concrete delivered to the job, temperature monitoring plan, concrete specifications, curing methods, and early age protection to prevent distress of the concrete. Through daily monitoring of the ambient and internal concrete temperatures, CA was able to provide the General Contractor with guidelines for proceeding with construction as quickly as possible while ensuring that the concrete did not experience any cracking due to thermally-induced stresses.

Emmet Shelton Bridge Structural Analysis and Rehabilitation

CA performed a four phase investigation of an existing 1940’s composite steel and concrete bridge spanning the Colorado River in Austin, Texas. Phase I consisted of  full-scale instrumentation and load testing, including performing a preliminary structural analysis and providing  consulting engineering services related to the emergency transport of heavy loads across the bridge well in excess of the rated capacity of the structure. Phase II included a condition survey of the superstructure and substructure which involved photographic documentation of the existing structural conditions, testing of the existing concrete, underwater inspection of the bridge foundation, installation of strain gauge monitoring devices, and addressing safety issues regarding traffic. Phase III involved the continued monitoring of the in-service behavior of the bridge in addition to performing a life-cycle analysis of the structure in its present condition based on the field data obtained in Phase II. Phase IV consisted of the design of repairs for the superstructure and substructure and construction administration and inspection of the implementation of the rehabilitation.

Non-Destructive Testing Services at Dos Hermanos Bridge

The Dos Hermanos Bridge structure, built in 1981, is one of the two ground-level links between the Islands of San Juan and Puerto Rico. As a result of the severe marine environment exposure conditions, a few years after its completion, the bridge showed signs of early deterioration including severe corrosion of the concrete reinforcement in both the cast-in-place and the precast, prestressed structural members. CA performed a field condition survey and assessment of the structural integrity and safety of the structure including, among other things, destructive and non-destructive concrete testing, chloride ion content testing to determine the chloride ion penetration into the concrete, and cover meter scanning to determine the location of existing reinforcement. Furthermore, a service life cost estimate analysis and predicted service life expectancy was prepared based on various modeling techniques considering the in-service conditions, the implementation of different concrete restoration and rehabilitation techniques, and the actual properties, characteristics, and performance of the concrete.