Distribution Warehouse, Slab Stabilization and Joint Fill

A large retailer distribution center, a 1,270,000 square feet warehouse and storage facility located in Pueblo Colorado, underwent a large renovation and rehabilitation project in September of 2015. The building was acquired in 1986 and has had several additions to the original warehouse area.

The Problem

In July of 2015 a site survey revealed a large array of structural deficiencies including drainage issues, spalling issues of interior concrete surfaces, water infiltration, settlement of concrete floor slabs, building movement, problems with doors not shutting, cracking in the precast wall panels above bay doors, and joint filler deterioration. Roche Constructors, a highly reputable Commercial Contractor located in Greeley Colorado was awarded the contract to coordinate and provide rehabilitation of the building. CST partnered with Roche to perform the slab lifting, soil stabilization, structural repair and joint filler portions of work.

Settlement of close to 6,000 square feet of floor slab had created a bird bath in the main north/south runway at the east side of the building near the busiest loading dock bays. This area is continually pounded by loaded forklifts carrying product to and from storage areas. Soil testing determined a weak soil zone 10 to 12 feet below the slab in this area that likely contributed to the settlement. The joint sealant in the control joints in a large portion of the floor slabs had lost cohesion and needed to be replaced as well.

15 areas in the precast walls located above the large overhead dock doors had developed cracks due to impacts from large semis unloading freight.

Factors for Consideration

There were many factors CST had to consider while planning and executing the stabilization and repairs of the distribution center. Roughly 25% of the floor area that needed lifting was in the main runway. Injection hoses would need to be run along this area, but not interfere with forklift traffic. Due to the approaching holiday season, the warehouse was receiving more inventory than usual and areas had to be accessible for unloading and storing freight. Because of increased shipments and need for access to the additional storage areas, the work window was reduced to accommodate receiving personnel and provide access to the additional storage areas of the warehouse.

The original joint fill compound used in the floor slab control joints had lost cohesion in a large portion of the slab area. In order to find the most effective and long lasting solution that wouldn’t require re-application, the product specified for sealing would need to be analyzed to ensure durability.

The sheer size of the warehouse itself posed a problem with communicating between crews and warehouse personnel. Two-way radios were issued which allowed easier communication when a question arose during repairs and attributed to a successful and smooth running project.

Method/Process Applied

The CST technologies were used to lift the warehouse floor slabs and stabilize the soils beneath the slabs. In addition, 3 columns were also stabilized and lifted to match the slab elevation. The CST process uses a high density expanding structural polymer that is injected through small probes into the soils below the concrete slabs. The polymer fills voids, increases bearing capacity of the soil, and lifts the concrete. Soils were also stabilized at depth of weakness to ensure no future settlement of the area. Careful monitoring at the surface was performed during injections to control the stabilization and lifting process with surgical accuracy. The CST soil stabilization and concrete slab lifting processes provide a permanent solution for settled concrete slabs because they treat the real problem, the underlying soils.

CST worked with the retailer’s engineering staff to determine a more effective and stronger compound than what was originally specified to ensure a more permanent adhesion and performance of the joint filler for the control joints. Areas were sectioned off and treated as to not disrupt warehouse traffic. Old material was removed from the joints, backer rod and sealer were then installed with areas marked off and allowed to cure before traffic was allowed back on the area which ensured good adhesion and strength of the treated joints.

To address the cracks in the precast walls , CST employed a composite repair system designed to provide shear and flexural strengthening to compromised and damaged buildings and infrastructure. The system uses an extremely strong carbon fiber matrix that was applied to the cracked and deteriorated areas of the precast walls. The repair system is significantly faster and less expensive than traditional repairs or replacement. Interior and exterior repairs were made to strengthen and protect the precast walls from further deterioration.

Result

The entire 6,000 SF slab area was lifted back to near original elevation and columns were stabilized and lifted to align with stabilized floor slabs, control joints were treated and filled and cracks in the precast walls were repaired in the time frame required. Soils beneath the distribution center warehouse were permanently stabilized, the concrete slabs and columns were realigned eliminating trip hazards and excessive wear and tear to equipment traveling over the areas. The structural integrity of the precast walls was restored. All processes were done with zero excavation and very little disturbance to the operations within the warehouse. Work was completed while leaving one lane open at all times to fork lift traffic. Due to the fast curing time and non-disruptive CST processes, traffic was allowed back onto the treated areas within 15 minutes following stabilization. The owner of this project and the owner’s representative, Roche Construction were very pleased with the professional, quality repairs performed by CST on the distribution center warehouse.