The Grand Pour: Inside the Wilshire Grand Project’s Record-Breaking Concrete Mat Foundation

At 73 stories and 1,100 feet in height, the Wilshire Grand project in downtown Los Angeles stands as the tallest structure west of the Mississippi River. Before its iconic tower could rise, however, the project required one of the most ambitious concrete placement operations ever attempted: a continuous 21,200-cubic-yard mat pour set 80 to 95 feet below street level. For construction professionals planning large-scale foundations, understanding how teams like Turner Construction and Conco pulled off this feat offers valuable lessons in logistics, equipment selection, and quality control. For those working on smaller projects, our guide on How to Pour Concrete for Pile Foundation Pdf covers the fundamentals of deep foundation work.

Planning the Largest Continuous Concrete Pour in History

The scale of the Wilshire Grand foundation demanded meticulous advance planning. The mat slab that would support the 73-story tower required a continuous pour to eliminate cold joints and ensure monolithic structural behavior. The structural engineering firm Brandow & Johnston specified a continuous placement approach specifically to guarantee that the mat foundation would develop its maximum design strength.

Site Preparation Before the Pour

For months before the record-breaking event, crews worked to prepare the site for the massive concrete placement. The excavation involved:

• Digging an 18-foot-deep pit at the base of the excavation, which sat 80-95 feet below street level
• Installing seven million pounds of reinforcing steel to create the rebar mat that would reinforce the slab
• Positioning concrete pumps both inside the excavation and at street level to enable continuous delivery
• Mapping alternate truck routes to account for Los Angeles freeway congestion

The depth of the pour location added significant complexity. Equipment had to be carefully selected to reach the placement points while maintaining steady flow rates throughout the 18.5-hour operation.

Logistical Coordination for a Downtown Site

Given that Los Angeles is the second most populous city in the United States, the construction team anticipated major logistical challenges when planning a large mat pour at a downtown location. To minimize the impact on surrounding businesses and residents, the team scheduled the pour to begin on a Saturday evening and conclude around noon the following day.

Michael Marchesano, Turner’s general superintendent, emphasized the time-sensitive nature of concrete delivery: “Because the concrete must be poured within 90 minutes of being mixed, trucks had to arrive on time. In case of freeway jams, alternate routes were mapped.” This 90-minute window placed enormous pressure on the supply chain and required real-time coordination across eight concrete batch plants within a 20-mile radius.

Equipment Strategy: Deploying 19 Concrete Pumps for Continuous Operation

Central to the success of the Grand Pour was an intricate equipment layout involving 19 concrete pumps working in relay formation. The equipment fleet was built entirely around Putzmeister machinery, chosen for its durability and reliability under continuous operation.

Pump Configuration and Placement

The pump layout was designed as a multi-stage relay system. Six pumps positioned at street level fed concrete down into the excavation, where six more pumps received and redistributed the material to the placement points. The configuration included:

• 12 Putzmeister truck-mounted concrete boom pumps ranging from 32Z to 47Z meters in reach
• Two Putzmeister MX 34/38Z Placing Boom Towers positioned inside the excavation
• Two Putzmeister BSA 14000 trailer-mounted concrete pumps operating at ground level
• Additional pumps at street level that relayed concrete to the pumps below

This multi-level relay approach allowed the team to maintain uninterrupted flow despite the 80-foot vertical drop from street level to the placement point. The table below summarizes the complete Putzmeister equipment deployed for the pour.

“We utilized Putzmeister equipment due to its durability and reliability,” said Marchesano. “With a continuous pour of this magnitude, you need to be able to count on your equipment to keep doing its job, even under demanding conditions.”

Putzmeister Equipment in the Vertical Construction Phase

Importantly, the investment in placing boom towers paid dividends beyond the mat pour. Both Putzmeister MX 34/38Z Placing Boom Towers that handled the foundation placement remained in position as the crew began building upward. The towers continued to serve the project during construction of the attached parking structure and the 73-story tower, eliminating the need for additional pump setup for the vertical phases.

Concrete Mix Design and Quality Control for the Record Pour

The structural integrity of a mat foundation of this scale depends heavily on the concrete mix design and the curing regime that follows placement. The Brandow & Johnston engineering team specified a special 6,000 psi mix with a 90-day design strength, chosen specifically to support the continuous pour strategy.

Managing Heat of Hydration

One of the greatest risks in a mass concrete placement of this volume is thermal cracking caused by the heat generated during cement hydration. When concrete cures, the chemical reaction between cement and water releases significant heat. In a 21,200-cubic-yard placement, that heat can build up to dangerous levels if not controlled.

The team addressed this challenge through two primary measures:

1. Special admixtures were added to the concrete mix to regulate the temperature during the hydration process. These admixtures ensured that internal temperatures never exceeded the parameters designed for the mix.
2. A thermal control system combined with a cure blanket was applied immediately after placement and maintained for 15 days. This system prevented rapid cooling that could cause thermal shock and cracking.

Without these admixtures and thermal controls, the mat slab could have experienced significant thermal cracking and lower final strength, which would have compromised the structural integrity of the entire foundation.

Continuous Pour vs. Sequential Placement

The decision to pour continuously rather than in sequential lifts was driven by structural engineering requirements. A continuous pour ensures that the entire mat cures at the same rate, producing uniform strength properties throughout the slab. Sequential placement creates cold joints between lifts, which can become weak planes in a heavily loaded foundation.

For professionals handling smaller placements, the same quality control principles apply. Proper curing, mix design verification, and attention to thermal management are critical whether you are pouring a skyscraper foundation or a residential slab. Our guide on how to Pour a Concrete Slab for a Shed covers the practical steps for smaller scale projects, and for uneven terrain, see our article on how to Pour Concrete Sloped Surface.

Technology and Supply Chain Lessons from the Grand Pour

Coordinating 227 ready mix trucks making more than 2,100 trips across eight concrete plants within a 20-mile radius required real-time visibility across the entire supply chain. Each truck made between 10 and 14 concrete drops, traveling through the night to maintain the relentless 18.5-hour placement schedule. In total, the operation placed 82 million pounds of concrete.

Real-Time Logistics with TRUCKAST

The Wilshire Grand project served as a proving ground for a new mobile application called TRUCKAST, designed specifically to solve the contractor-supplier communication gap. Developed by CEO Todd Davis, the app allowed every stakeholder in the pour to stay connected in real time.

The mobile app leveraged legacy data from existing dispatch and billing systems and delivered that information contextually through the application. During the Wilshire Grand pour, the TRUCKAST platform enabled:

• The concrete producer to monitor truck locations and delivery status
• The construction manager to track arrival times against the 90-minute mixing window
• Owners and developers to observe progress without being on site
• The Guinness World Records adjudicator to verify the continuous nature of the pour
• Truck drivers to receive routing updates based on real-time traffic conditions

“We solved the contractor/supplier problem — where is my truck,” Davis explained. “The transparency and trust of both parties improves with real time communication.” At the peak of the pour, as many as 17 trucks were unloading concrete simultaneously at the site.

Key Project Participants

The Grand Pour brought together a team of industry leaders from across the construction sector:

1. Owner/Developer: Korean Air Lines Co., Ltd., Seoul, South Korea
2. General Contractor: Turner Construction Company, New York, N.Y.
3. Equipment Owner: The Conco Construction Companies, Concord, Calif.
4. Ready Mix Concrete Provider: Catalina Pacific Concrete Company, Glendora, Calif.
5. Structural Engineering: Brandow & Johnston
6. Pump Equipment: Putzmeister America

The first batch of concrete delivered to the site came from a plant in Vernon, California, a facility that holds the distinction of having poured the first concrete in Southern California history. This symbolic connection between past and present underscored the historic nature of the pour.

The Guinness World Record and Beyond

The mat pour officially qualified as the largest continuous concrete pour in history and claimed a GUINNESS WORLD RECORD. For the construction teams involved, the record validated years of planning and millions of dollars in equipment investment. For the industry as a whole, the Wilshire Grand pour demonstrated what is achievable when advanced equipment, carefully engineered mix designs, and real-time logistics technology converge on a single project.

Davis noted that TRUCKAST’s market research indicated the concrete industry was the right starting point because of the short delivery cycle and the high volume of stakeholders involved in each pour. The company’s next goal is to extend the platform to other bulk materials, including asphalt, cement, and aggregates. For contractors planning their own concrete projects, understanding the basics of proper placement is essential. Learn how to Pour New Concrete Over Old Concrete Surface for guidance on overlay and repair applications.

The Wilshire Grand Tower opened in 2017 as the tallest building west of the Mississippi, a standing testament to what a well-planned, well-executed concrete placement can support.