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Inspection and Rehabilitation of Underground Tunnel System

The Govalle Tunnel is an approximately 8 mile long, 96-inch diameter, cast-in-place concrete tunnel at an average depth of 100 feet that conveys wastewater generated in central and southeast Austin, Texas to the South Austin Regional Wastewater Plant. Inspections performed by the City of Austin in 2002 identified rehabilitation needs for the tunnel system. Rehabilitation work included structural repair of large diameter and deep shafts and laterals using a cementitious repair material followed by the application of an epoxy protective system. The purpose of these repairs was to remediate the impacts of concrete deterioration due to exposure to sulfates and steel reinforcement corrosion and to protect from future deterioration. CA was retained by the City of Austin to determine the cause(s) and/or contributing factors resulting in the failure of the rehabilitation work using an approved repair mortar. Among the most relevant issues investigated were the quality of the substrate surface preparation, repair materials characteristics and properties, repair practices, and behavior, performance and curing requirements of the repair mortar at different temperatures.

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Forensic Investigation into Distress of Rigid Pavement

This project consisted of various segments of approximately 9.7 miles of Portland Cement Concrete Pavement (PCCP) on Road US 64/87, located in Union County near Des Moines, New Mexico. The project was divided into East Bound Lane and West Bound Lane sections each consisting of two traffic lanes. CA was retained to identify the possible cause(s) and/or contributing factor(s) of the distress in the PCCP, as well as assess the repairs made during and after construction. The investigation included on site evaluation, photographic documentation, analysis of technical documents, among others. CA was able to identify segments of most distress associated with concrete placement and location, and the cause(s) of the distress associated with the PCCP.

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Concrete Basement Wall Assessment and Repair

Carrasquillo Associates (CA) assessed the condition of a 22 in. thick reinforced concrete basement wall and pilasters during construction after irregularities were observed on the surface of the concrete wall. CA determined the extent of the deficiencies and developed a repair protocol for the wall. CA’s investigation of the wall included a visual survey, non-destructive testing (NDT) using ultrasonic echo 3D tomography, and concrete core sampling for visual examination and compressive strength testing. CA non-destructively scanned the wall using ultrasonic echo 3D tomography, a method that uses ultrasonic shear waves to locate internal defects, reinforcement, and the back surface of the concrete. The majority of the NDT testing data did not indicate the presence of internal defects within the wall. Verification cores and compressive strength testing from several of these areas confirmed the absence of internal defects and/or low strength concrete. At CA’s recommendation, the project team approved the repair of the wall.

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Investigation and Repair of Rain-Damaged Concrete

Carrasquillo Associates investigated and characterized the surface distress occurring at an elevated post-tensioned concrete slab in a parking garage that is part of a high-rise building under construction in downtown Austin, Texas. CA’s investigation included an examination of the extent of distress or unsound concrete in an area within one level of the parking garage equal to approximately 10,000 square feet, where rain had affected the fresh concrete surface soon after it had been placed. CA conducted a site visit to the parking garage to perform a visual examination and condition survey, and to obtain core samples from the concrete deck. The cores were studied by a concrete petrographer, who determined the extent of rain damage within the depth of each core. CA utilized this determination in developing a repair plan for the affected concrete surface to restore its serviceability and long-term durability. This project provides an example of CA’s expertise in recognizing a structural or materials problem and its root cause, assessing how it will affect the structure, and offering a repair solution that efficiently and reliably restores the structure.

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Assessment and Repair of Cast-in-Place Concrete Framing

Carrasquillo Associates investigated deficiencies observed on the surface of the concrete for the second floor cast-in-place concrete framing, which consisted of conventionally reinforced beams, girders, column tops, and the second floor slab. CA reviewed the condition of the cast-in-place concrete to determine the extent of the deficiencies, to develop a repair protocol, and to selectively observe and document the repair work. CA’s investigation included a visual condition survey, non-destructive testing (NDT) using Ultrasonic Pulse Velocity (UPV) equipment, and concrete core sampling. CA’s visual condition survey identified several types of possible deficiencies. These included surface honeycombing, poor consolidation, internal voids, and visible lift lines and/or cold joints. CA demonstrated that the majority of the observed deficiencies were near surface and did not impact the structural integrity of the concrete structure. Based on CA’s recommendations, the project team decided that all of the observed deficiencies could be repaired.

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Foundation Movements and Welding Defects in Precast Parking Garage

Carrasquillo Associates (CA) was retained in 2013 to investigate alleged construction defects in a precast parking garage supported by drilled piers near Austin, TX. As part of CA’s investigation, welds were inspected at broken precast connections, relative elevation surveys were performed near distressed areas, cracking was mapped throughout the structure, and a comprehensive finite element method (FEM) model was created for the garage. The FEM model allowed CA to analyze the effect of the measured support settlements to evaluate the cause(s) of the observed distress. Using this information, CA also evaluated the repair scheme being implemented to address the distressed areas throughout the structure.

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Causes and Ramifications of Distress in Post-Tensioned Multimodal Transit Facility

Carrasquillo Associates (CA) was retained in 2016 to investigate distress in a multimodal transportation hub located in the northeast United States.  The cast-in-place structure consisted of a slab on ground and two elevated slabs supported by a concrete frame. The elevated slabs as well as the concrete beams and girders were post-tensioned (PT). CA investigated concerns related to cracking in the concrete slab and frame, reinforcement cover, and concrete durability. As part of the investigation, CA made a site visit to the structure and also reviewed numerous documents including, among others, design drawings, specifications, photographs, shop drawings, expert reports, testing reports, and communications between parties. CA’s investigation helped to identify the causes and ramifications of the observed distress which allowed the parties to come to an agreement regarding the damages.

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Crane Rail Wear and Misalignment

Carrasquillo Associates (CA) was retained in 2014 to investigate unusual wear on crane rails in a steel processing plant in Pennsylvania. CA conducted an on-site investigation to measure the severity of the crane rail wear and to determine its cause. Custom crane rail measuring devices were fabricated at a machine shop in Austin, TX for this purpose. In addition, CA reviewed numerous surveying reports to verify dimensional compliance between laser surveys, project specifications and industry standards. Life cycle estimates of the crane rails were made based on the information collected during the site visit and research conducted by the US DOT.

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Alkali-Silica Reaction (ASR) in Pier Structure

Carrasquillo Associates (CA) was retained in 2012 to investigate concerns about the structural integrity and long term performance of a pier structure in Honduras and to determine the deterioration mechanisms affecting the durability, the structural safety and useful life of the structure. The investigation into the structure included visual inspection, crack monitoring, concrete sampling, petrographic examination, chloride testing, structural analysis, and half-cell testing among other items. Based on the testing performed, the internal concrete expansion damage mechanism was identified and the remaining service life of the structural performance of the structure was assessed. Further, several alternatives for restoring the service life and the facility were evaluated. This allowed the client to better understand the cause of the distress that was being observed and what needed to be done to allow the structure to continue to operate safely moving forward.

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Forensic Engineering Investigation & Analysis of Bridge Overlay Failure

The Pulaski Skyway Bridge Project consisted of a steel truss bridge supporting a concrete bridge deck with repairs where the top 1.5 inches of concrete bridge deck was replaced with a latex modified concrete topping along the entire length. Shortly after, the repairs began to exhibit premature failure in the form of reflective cracking around the perimeter of the repaired area, then debonding, followed by cracking of the patch repair material causing eventual potholes in the bridge deck. CA’s investigation involved, among others, review of daily log reports, expert reports, and other relevant documents, and a site visit during which a visual condition survey was performed to determine the cause(s) of the observed premature patch repair failures in the bridge deck.