While the exterior construction progress of Great Gulf's One Bloor East has garnered significant attention throughout the City, the interior of the building houses one of the project's most innovative features—away from public eyes. During our tour of the 76-storey project, however, UrbanToronto got an 'inside' look at the construction site, beginning with our walk through the podium.

Looking skyward from the corner of Bloor and Yonge, image by Marcus Mitanis

Continuing our coverage of the 257-metre tower, we now take a look at one aspect of construction at the site, particularly Verdi Alliance's concrete pump, which channels a continuous supply of viscous concrete to the upper levels, hundreds of metres above the base of the building.

At ground level, the procession of concrete mixing trucks supplies the building's needs, but whereas most buildings have a crane waiting to hoist bucketloads skywards, One Bloor is too tall for that method to be efficient. Here instead, the concrete mix is funnelled from the trucks the through the powerful pump mechanism (below), which pushes the material up a pipe which runs the entire length of the Hariri Pontarini Architects-designed tower's 76 habitable floors.

The trucks funnel concrete into the pumping mechanism, image by Marcus Mitanis

The Pumpcrete equipment uses Schwing technology to carry the concrete up the 257-metre tower, moving the material through a pipe routed alongside the tower's elevator shafts. Our video gives you a feel for the power of this mechanism.

Running alongside the elevator, the highly pressurized pump is periodically lubricated with water, helping the dense concrete travel up the length of the tower.

The pump reaches the mechanical levels, image by Marcus Mitanis

As opposed to the more common bucket concrete method—which hoists the material up the length of a tower—pump concrete allows for a faster, steadier, and less labour-intensive delivery system. Above the 76th floor, the pipe pours out at the tower's mechanical levels (above), where concrete is now being placed.

Shoring on the 76th floor, image by Marcus Mitanis

On the 76th floor, shoring rods can be seen reinforcing the new floor slab above as its recently placed concrete cures (above), while the fly forms remain in place on another part of the floor where the concrete was even more recently placed (below).

Shoring rods hold the 77th floor forms above, image by Marcus Mitanis

Concrete is never just poured into a form without first having a virtual cage of steel reinforcing bars (rebar) laid out and wired together in the form—rebar encased in cured concrete gives the slab enormous strength—so having the rebar close at hand is important for the construction crews. While earlier in the construction process of One Bloor the roof of the podium was used to store these materials, the podium is now far below, and it makes more sense to have the materials waiting closer to where they are going to be needed.

Temporary materials storage, 73 floors in the air, image by Craig White

To that end, a special cantilevered platform was installed recently at the 73rd floor. Above, it's seen from the ground, while below, it's seen from the 76th floor.

Temporary materials storage, 73 floors in the air, image by Marcus Mitanis

The 76th floor was also being used to store construction equipment for the ongoing work on the two uppermost levels above, also known as the mechanical penthouse (below).

Shoring rods and construction equipment overlook the skyline, image by Marcus Mitanis

That's it regarding the concrete and rebar, but we will return with looks at One Bloor East's building envelope and balconies, and at the penthouse floors which offer panoramic views of the city from a high elevation. In the meantime, check out our dataBase file—linked below—for renderings and more information on One Bloor. You can join in on the discussion in the associated Forum threads, or leave a comment in the space provided on this page.