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 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.

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.

Slab-On-Grade Distress Investigation and Analysis

The project consisted of two aircraft assembly hangars consisting of 8 in. thick cast-in-place slabs-on-grade with 0.5 in. wide and 2 in. deep joints.  The facilities were constructed during the period from 2004 to 2005.  CA was retained to conduct an investigation and determine the cause(s) of the distress occurring at the joints that consisted of the joint sealant protruding up to a 0.5 in. above the surface of the slab-on-grade.  CA’s investigation consisted, among others, of several site visits, concrete core sampling at the joint sealant locations, shore hardness testing, evaluation and different joint sealant, test program, and condition surveys.  CA determined the cause(s) of the distress and provided recommendations for remediation of the distress including material selection and installation procedures and recommendation for joint detailing for future construction.

Alkali-Silica Reaction Residential Home

CA was retained in order to investigate the long term performance and possible remediation alternatives for the cast-in-place concrete slab-on-grade foundation at the residence affected by alkali-silica reaction (ASR). Shortly after placement, the foundation exhibited signs of ASR by exuding the slippery gel product throughout the slab causing a safety hazard for the owners. CA was tasked with determining the extent of the damage as well as provide a set of guidelines for repair. CA’s investigation consisted of document review of concrete delivery records, photographic evidence of the site, litigation documents, concrete sampling,  petrographic examination, and three site visits to the residence.

NDT Assessment, and Repair of Concrete Basement Wall

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.

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.

Residential Alkali Silica Reaction Distress Investigation

CA investigated a residential concrete foundation slab where the interior finished concrete floor exhibited visible distress consisting of exudations on the surface of the concrete. These exudations included some consisting of clear, sticky gel and others consisting of hardened, opaque-white deposits. CA completed a condition survey, elevation survey, and concrete core sampling on site. The condition survey showed concentrated distress at and immediately around the grade beams where the vapor barrier was discontinuous and little distress in the slab areas between grade beams. The petrographic examination of the cores found that the observed distress in the cores extracted from the distressed areas was the result of alkali‑silica reaction (ASR). In this case, the aggregate near the surface exuded the gel to the surface of the concrete. Due to the site grading in combination with the discontinuous vapor retarder, moisture was being transmitted through the concrete at the grade beams resulting in the ASR distress. The lack of ASR in the slab areas between the grade beams indicated that with adequate under-slab moisture-proofing, the concrete was performing adequately.

Warehouse Foundation Slab Distress

CA investigated claims of poor construction of a 160,000 sq. ft. warehouse foundation slab. CA completed a site visit to the warehouse to document and verify the general condition, geometry, and construction of the interior concrete slab on grade, exterior paving, and eastside retaining wall. CA completed a crack map of the interior, documented other forms of distress such as joint distress and honeycombing, documented the joint type, and measured the joint layout and depth. While completing the site visit, the removal and replacement of a portion of the interior slab on grade was being completed independent of CA’s work. CA observed portions of this work and examined select portions of the slab on grade which were removed to determine concrete thickness and reinforcement location and depth. CA developed alternative repair strategies for the observed distress.

Forensic Investigation of Exterior Brick Masonry Deterioration

Carrasquillo Associates investigated widespread distress in exterior brick masonry at two residences in Midland, Texas. CA reviewed, evaluated, and synthesized extensive literature pertaining to brick mineralogy and deterioration mechanisms in order to fully understand the many facets and possible root causes of the observed distress and ongoing mechanisms of deterioration. CA conducted multiple site visits to study, observe, and document the brick masonry deterioration and to obtain numerous brick samples from the exterior residential façade and landscaping features. Several brick samples were subsequently tested for physical properties according to ASTM standards, including absorption and compressive strength. The chemical composition and mineralogy of several specimens were studied using x-ray fluorescent (XRF) and x-ray diffraction (XRD) techniques in order to comprehensively investigate the types of raw materials used in production and to assess the degree of vitrification achieved during brick firing. This project provides an example of CA’s expertise in deciphering the contributing players in material degradation, such as brick masonry deterioration, and displays CA’s ability to manage material testing through multiple laboratories for one particular study or project.

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.