Cell-Crete Corporation

Caltrans was concerned about the fill load on the tunnel roof of Doyle Drive on Highway 101. Lightweight cellular concrete (LCC) was selected because it was lighter than natural fill and no compaction was needed.

Cell-Crete Corporation was subcontracted to perform the tunnel roof fill job with 27 PCF (pounds per cubic foot) (40+PSI) LCC material.

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This job site was a challenge because it was over 45′ below ground level. Many obstacles were prevented using typical fill materials. It was in a busy area of town limited on each side by buildings and street access. Below the slab-on-grade, a drainage layer was needed. The typical conveyor system and truckload after truckload of material was considered infeasible due to the depth and schedule concerns of the pour area. The flowable nature of low-density cellular concrete (LDCC) was suggested as a value alternate to speed the construction process and assist in the drainage below the slab.

Cell-Crete was hired to pour permeable cellular concrete in four separate areas for a total of 1,800 cubic units (CY). Permeable cellular concrete was suggested as part of the drainage layers below the slab. Anticipated truck deliveries were reduced from 120 to 12. This was a major help in a project demanding trades to work together and accomplish a tight deadline. Cell-Crete set up equipment away from the normal delivery area and strung hoses along the shoring walls to the pour area. A darby finish was placed on top of the LDCC and vapor barrier used to reduce the telegraph cracking through to the slab-on-grade. This was completed in 8 days with 4 separate staging areas.

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The Hoquarton Slough in Tillamook, OR is an area of tidal flats next to downtown. It gets especially congested during the tourist season. The Oregon Department of Transportation (ODOT) determined the old three-lane bridge over Hoquarton Slough was in need of repairs, and because of traffic demands, a new four-lane bridge was contracted in 2015. A number of obstacles in the new bridge-building process was evaluated: being in close proximity to existing businesses at risk of sinking, poor soil conditions surrounding each end of the bridge, and the contaminated soils from years of adjacent property used in the lumber industry. Low-density cellular concrete (LDCC) was then chosen as the load reduction material for each bridge approach because its track record as a load-reduction method has been successfully used since the 1970s.

Cell-Crete was subcontracted in 2016 to pour approximately 12,000 CY over the duration of 2.5 years. LDCC was poured under from each of the bridge approaches up to the bridge abutments. For the wing walls, through the general contractor, Cell-Crete suggested using a gabion-basket-style wall system to replace the sheet pile that was planned to stay in place. This saved time and money through a VE Alternate. The overall load reduction used an approximately net-zero added load not including a factor of safety. Cell-Crete used a maximum 30 PCF (pounds per cubic foot) mix to achieve the needed load design.

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SoFi Stadium, Inglewood, CA

Construction is finished for the highly anticipated SoFi Stadium in LA. The estimated $5 billion project, located at the former Hollywood Park racetrack, now serves as the home for the LA Rams and LA Chargers and seats over 70,000 NFL fans. To make way for this massive structure, a substantial amount of ground preparation, excavation and improvements were made to the existing site. More than 120,000 cubic yards of lightweight cellular concrete (also known as LCC or foamed concrete) was placed during the construction of SoFi Stadium.

Due to the numerous benefits and versatility that lightweight cellular concrete offers, we placed LCC for different applications on this single job: pipeline abandonment, a quarter-mile trench, canyon retaining wall backfills and pile cap fill.

One of the applications needed was to abandon an existing sewer line. The flowable nature of cellular concrete (also known as foamed concrete) allows it to easily be pumped into a pipeline. One of the risks with abandoning a pipe is the potential of damage to the structure, but with LCC the material can be pumped at lower pressures minimizing the risk of damage to the pipe.

The project’s proposed improvements called for an increase in cover of over 10′ from existing grade elevation. This would exceed the maximum vertical allowable load cover on an existing 87″ RCP pipeline. 1400′ of trench was excavated to be backfilled with Class II cellular concrete over the existing pipe. Class II cellular concrete is about 1/4 the weight of traditional fill and was placed above the RCP pipeline in lieu of the existing fill to reduce/equal the existing vertical load while raising grade to proposed elevation; no additional load is being applied to the existing RCP pipeline after increasing the fill cover depth by over 10′. The pour took place in sections of 100′ (L) x 11′ (W) x 11′ (H) and was completed in one lift; each section took only a few hours to complete.

LCC was placed at the East, West, and North canyon walls of the stadium. Cellular concrete (also referred to as foamed concrete) backfill was required for canyon retaining walls with a design height greater than or equal to 12’. LCC provides a static weight reduction of up to 75%, the result of this significant weight reduction is much lower consolidation settlements and reduced inertial loads and dynamic compression during earthquakes.

To improve seismic performance of the roof structure, columns connected to butterfly caps were placed around the footprint of the stadium. In the design of the stadium, extra measures were taken to support the stadiums roof that is vulnerable to earthquakes. Lightweight cellular concrete (foamed cellular concrete) was poured around the pile caps to allow for movement and serve as a crushable material during seismic activity.

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The Roosevelt Station is the latest in a string of projects with Sound Transit (link light rail service in Seattle) utilizing Cellular Concrete Fill (CCF), also known as low-density cellular concrete (LDCC). The Northlink Light Rail Extension has stations 30’–50’ below ground level. LDCC was selected to reduce the dead load on the new underground station below and has been the choice for the past 4 Northlink stations due to its lightweight properties, flowable nature and competitive cost compared to alternatives in the local market.

Cell-Crete was subcontracted in 2017 and began pouring approximately 8,500 CY in March of 2018. Due to the timeline and utilities, Cell-Crete poured in 2’–3′ depths depending on areas available. The total footprint will approximately be 15′ in depth across 2 blocks. The LDCC will support the traffic above on NE 12th Street. Cell-Crete’s portion of the project was completed on schedule in July of 2018. The company’s next scheduled station was the Brooklyn Station, which began in 2019.

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The Shell dock-unloading pier in Portland, OR was no longer in use. Multiple gas lines were built over the years from the old dock to the gas storage facility (approx. 2,500’ away). These six lines went under a major railroad car manufacturer and the production schedule couldn’t be stopped to abandon them. When using a controlled density fill (CDF), the maximum distance to flow material is 300’. An abandonment with CDF would’ve halted railcar production and added weeks—if not months—to the abandonment process schedule.

Cell-Crete was contacted by the general contractor with knowledge of the flowable nature of low-density cellular concrete (LDCC). The lines were cleaned of any excess fuel, and the general contractor created bulkheads at each end to push LDCC until it was completely full. Cell-Crete monitored pressure in lines to minimize the potential for bulkhead leakage or heaving. All lines were completed in one day with an extra day to fill any auxiliary lines.

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