Innovative Concrete Mixes and Delivery Improve Sustainability of Drexel’s New Tower
Drexel University’s new Academic Tower is beginning construction in uCity Square, West Philadelphia’s multimillion-square-foot academic, tech-based, mixed-use community. This 450,000 sq ft, block-long building will bring many of Drexel’s health-related programs under one roof.
Drexel has a strong commitment to sustainability and responsible building principles. As the first university in the United States to commit to using Green Globes, the environmental impact monitoring system, and achieving Gold status for its first LEED-certified building in 2012, it was only natural for them to look for sustainable solutions for Academic Tower. To help work toward LEED certification, designers selected portland-limestone cement (PLC) and sourced concrete materials locally.
PLC mixtures can reduce the embodied carbon of concrete mixtures by up to 10% while delivering the same performance characteristics as ordinary portland cement (OPC). Some phases of this development will use 25% Class F fly ash as a supplementary cementitious material (SCM) to reduce CO2 emissions from concrete further—up to 35%. And using two ports on the nearby Delaware River to deliver sand and stone by barge, hundreds of trucks can be removed from roadways to reduce cost and cut pollution in the community.
The tower’s plans require 11,000 cu yd of concrete, comprising 2,900 cu yd of 5,000 psi normal-weight concrete for the foundation and 7,000 cu yd of 4,500 psi lightweight concrete for the deck slabs—all made using PLC. The material supplier notes that PLC works well with lightweight aggregate, is advantageous for lightweight concrete, and that clients like how the reduced bleed water enables expedited finishing operations. Likewise, the concrete contractor was surprised and pleased with the performance. “As we started to use the new, more sustainable mixtures, our guys didn’t say anything or notice any difference in the material from OPC concrete. The environmental impact is definitely good for our business, and the LEED aspect helps our client and the owner.”