July 10th, 2016 marked the completion of a major phase in the construction of the W Hotel located 1414 Chestnut Street in Philadelphia. The hotel which is slated to open in 2017 will be the largest concrete structure in Philadelphia history. Tudor Perini, the general contractor for the building, teamed up with TP Carney the concrete contractor and Silvi Concrete to pour the largest continuous concrete pour in Philadelphia history.

Silvi Ready Mix

Driver waits in line to pour The W Hotel in Philadelphia PA

The concrete foundation for the new hotel is 20,000 square feet and roughly nine feet thick. The foundation contained 25,200,000 pounds of concrete. Eventually the surface of this concrete foundation will act as the bottom floor of the hotel parking garage. Due to the proximity of the heavily congested City Hall, the construction of this foundation was a logistical nightmare. The city of Philadelphia shut down 4 major streets 12:01 AM on Saturday morning until 11:59 PM on Sunday night.
Silvi Concrete in Philadelphia PA

Looking down South 15th St, Silvi front discharge mixers unloading to boom pumps.

The 10,000 psi mix design and temperature control requirements for this pour is arguably the most complex design the city has ever seen. The core of the 9 foot thick slab had to be limited to 154 degrees. In order to combat concretes natural heat of hydration process Carney placed 6 miles of cooling tubes throughout the rebar which ran chilled water for 1 week following the completion of the pour. In addition, Silvi was required to create a 10,000 psi mix that had to contain 50% fly ash (356 pounds per yard) and deliver it below 90 degrees in the peak of summer. Fly ash dramatically slows down the hydration process of the concrete, which reduces the total heat generated in the core of the concrete. The engineer for the project was concerned with thermal cracking caused by high core temperatures and low exterior temperatures. This eliminated the use of more commonly used high strength cementitious products such as slag or silica fume. Silvi, being outside the city limits was called upon to perform the project with less than two weeks of notice because they were the only supplier with enough fly ash.

Due to the complexity of the mix design, size of the pour, and location of the hotel Silvi Concrete became the natural fit to supply the concrete. In order to complete the monolithic placement per the engineer’s specification, Silvi Concrete committed to deliver 5,868 yards over a 28 hour period. They would use 136 trucks and 4 12 yard central mix concrete plants. Since the mix contained almost as much fly ash as it did cement, Silvi stockpiled fly ash for weeks in portable blimps to meet the demand. In order to service their customers Monday morning, Silvi needed to amass enough sand, stone, and cement in addition to the volumes needed for the 5,868 yard W Hotel pour on Saturday.

Silvi Concrete and TP Carney

1414 Chestnut Street Philadelphia. Mat Foundation pour by Silvi Concrete, TP Carney, and Tudor Perini.

At 2:00 AM on the day of the placement the trucks started rolling on to the site. They began feeding four pump trucks strategically staged around the foundation including two, fifty-three meter pumps. The hole in the ground was fifty-four feet below street level and thus required very large pumps to reach various corners of the mat foundation. The combination of narrow one-way streets and open sidewalks for pedestrian foot traffic limited the number of pumps TP Carney could use for the pour. With only four total pumps and two smaller pumps which required three hundred feet of hard piping; the team was limited to pouring only 205 yards per hour. The limiting factor of 205 yards per hour made this pour a grueling 28.5 hours which required steady deliveries, patience, and commitment from everyone involved. After seeing the second sunrise in 28.5 hours the final truck arrived at 6:30 AM Sunday morning. Several members of the Silvi team, including the two owners, worked 48 hours straight from Friday morning to Sunday morning.
Silvi Concrete and The W Hotel

Nearing the end after a 28 hour pour in Philadelphia PA.

When asked about the success of the pour President Laurence Silvi II said, “It truly was a complete effort from everyone involved which allowed this pour to go perfectly”. Although this was only the second largest pour in the company’s history, it was far and away the most challenging making it Silvi’s biggest accomplishment to date.

SILVI CONCRETE is a member of The SILVI GROUP and headquartered in Fairless Hills, Pennsylvania. The SILVI GROUP was founded in 1946, employs over 350 people and consists of companies engaged in the manufacture of ready-mixed concrete, mining, cement, and real estate in southeastern PA and central and southern NJ