By Carrasquillo Associates 0 Comments

Reinforced Concrete Pavement Cracking

Carrasquillo Associates investigated cracking in a new reinforced concrete pavement. The cracking, consisting of regularly spaced longitudinal cracks occurring immediately over the reinforcement, was observed to have occurred a few days after the placement. CA’s analysis revealed an error in the dosage of retarder in some batches of the ready-mix concrete. In these batches, the retarder dosage was based on the entire weight of cementitious materials, rather than just the portland cement, resulting in excessive retardation. Excessive retardation made the concrete pavement susceptible to cracking due to shrinkage and dimensional movements. This propensity for cracking was exacerbated by the non-typical shallow top cover specified in the plans and drawings. CA’s investigation revealed that areas with the proper retarder dosage exhibited infrequent cracking, as compared to the extensive cracking in the remainder of the pavement where the retarder dosage was incorrect.

By Carrasquillo Associates 0 Comments

Residential Structure Investigations for Vibrations from Geophysical Exploration

Carrasquillo Associates served as a third-party, independent engineer in the evaluation of numerous residential structures in close proximity to geophysical exploration in Beaumont, TX. CA investigated the alleged distress and assessed whether the conditions were the result of geophysical exploration. The investigation included reviewing and analyzing information from applicable industry standards and relevant published literature regarding ground vibrations damage .

By Carrasquillo Associates 0 Comments

Progressive Distress Mechanism in Industrial Concrete Pavement

Carrasquillo Associates investigated distress in a 1,000,000 square foot concrete trucking pavement. CA’s investigation revealed two key findings. First, CA’s periodic condition surveys utilizing ASTM and FHWA practices provided clear evidence of a progressive distress mechanism. This distress mechanism began with joint sealant degradation and proceeded to water penetration, pumping, corner breaks, loss of support and faulting, and finally a completely broken pavement section. Second, CA determined that the rigid base which utilized on-site materials was mischaracterized as limestone during construction. In actuality, the base material was marl, which has a strength and appearance similar to limestone, but is moisture-sensitive, meaning strength is lost when the moisture content increases. In summary, CA’s investigation revealed that the failure to perform maintenance at the first manifestation of distress caused the premature pavement failures as a result of an improper base material

By Carrasquillo Associates 0 Comments

Repair of Slab-On-Grade Post-Tensioning

Carrasquillo Associates provided recommendations for the repair of a slab-on-grade after numerous post-tensioning tendons were cut during the installation of various plumbing trenches as part of an interior renovation project. As part of the repair process, CA documented the condition of the slab-on-grade by performing a crack map and elevation survey. These were performed both before and after the post-tensioning repairs to provide reassurance to the facility owner that the repairs had not negatively impacted the structure integrity of the slab-on-grade.  

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Construction Vibration Investigation

The project consisted of two residential structures, eight- and four-stories high, both supported by deep foundations with superstructures comprised of reinforced concrete and CMU block. The building between the two structures was demolished and construction of a new building, as well as some roadway construction, commenced. CA was retained to investigate allegations that this construction caused vibration-induced damage in the two residential structures.  CA’s activities included performing a condition survey of the exterior and reviewing established literature regarding distress on structures due to vibrations resulting from construction activities. CA determined there was no technically justifiable evidence to support that any of the alleged distress at the residential structures was caused by or affected by ground vibrations resulting from the construction activities.

By Carrasquillo Associates 0 Comments

Concrete Repairs under Severe Exposure at Wastewater Treatment Plant

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.

By Carrasquillo Associates 0 Comments

Cementitious Underlayment Deficiencies in Hospital Operating Rooms

CA investigated the quality of a cementitious underlayment installed as part of the finish out of the 11th and 12th floors of an existing 33-story hospital building. The elevated concrete structural slabs of these floors were covered with a variable thickness cementitious underlayment material, with the intent to achieve an adequate floor surface that would later receive final floor finishes such as tile or carpet. The owner observed that this underlayment exhibited an inconsistent appearance, variable color, a dusty/powdery surface, and a poor bond with the finished flooring. CA evaluated the underlayment and assessed the expected performance of the floor, specifically its integrity and ability to resist wear due to long-term loading from wheeled medical equipment. CA’s investigation included a walk-through, visual condition assessment, core sampling, petrographic examination, and bond pull-off testing. CA’s analysis resulted in the removal and replacement of the underlayment to ensure a quality long-term floor system in the operating rooms and associated support rooms.

By Carrasquillo Associates 0 Comments

Post-Tensioned Slab Blowout

CA investigated a large post-tensioning blowout which occurred during construction of a complicated, unique portion of a 30-story residential tower. CA’s investigation was focused on reviewing the design and construction of the Project, specifically the post-tensioned slabs, as well as documenting and analyzing the conditions and circumstances associated with the post-tensioning blowout and subsequent repair. CA determined that the structural design did not consider the complexity of the blowout location. No direction was provided regarding the anchorage placement with regard to the curved slab edge and the close proximity of the distributed and banded tendons. CA performed a finite element analysis which showed that the blowout location experienced overlapping bursting stresses from distributed tendons and the banded tendons. This, combined with restraint and an upward post-tensioning force, resulted in a localized region of amplified tensile stresses. These amplified stresses made the section susceptible to a post-tensioning blowout failure during construction. The repair of the blowout area incorporated numerous modifications as compared to the original design, including the relocation of the distributed tendons away from the banded tendon anchorages. During the repair, the blowout did not re-occur, confirming that the cause and/or contributing factors related to the design had been eliminated and addressed.

By Carrasquillo Associates 0 Comments

12-Story Mixed Occupancy Structure

The Project consisted of a twelve (12) story mixed occupancy structure located in Miami, Florida. It is approximately 606,800 square feet with retail space located on the ground floor, a seven-story parking garage structure, and four floors utilized for office space above the parking levels.

CA was retained by the General Contractor to conduct an investigation into several construction issues observed during and after construction. CA’s investigation included a review of the work performed by the subcontractors to determine whether it complied with the requirements of the Contract Documents. The elements of the structure investigated included various reinforced concrete members, safety barriers, masonry walls, and drainage provisions. CA performed a field condition survey, reviewed and analyzed relevant documents, and used 3D models to analyze the structure to determine whether the investigated structural elements complied with the contract documents.

By Carrasquillo Associates 0 Comments

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.