Projects

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.

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.

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.

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.