By some measurements, cement production alone is responsible for about 8% of human-caused carbon dioxide emissions every year. And so there is an imperative to find suitable low-carbon alternatives. Here is what is currently happening in the US (via Grist):

On Tuesday, Terra CO2 Technology was picked to receive a $52.6 million federal grant to build a new manufacturing plant just west of Salt Lake City. The company has devised a method that turns common minerals into additives that can help replace Portland cement — a key component in concrete, and one of the most carbon-intensive materials in the world.

In addition to this new facility, the company is set to start construction on its first plant in the Dallas-Fort Worth area:

The project is expected to break ground in January 2025 and begin shipping out materials by late summer 2026, Yearsley said. The facility will be capable of producing up to 240,000 metric tons of SCM [supplementary cementitious materials] per year when completed, or enough to serve roughly half of the local metropolitan market.

And all of this is part of a broader initiative by the US Department of Energy:

The Utah facility is one of 14 projects provisionally selected this week to receive $428 million in total awards from the U.S. Department of Energy’s Office of Manufacturing and Energy Supply Chains. The initiative, which is funded by the Bipartisan Infrastructure Law, aims to accelerate clean energy manufacturing in U.S. communities with decommissioned coal facilities. Officials said the projects are expected to create over 1,900 high-quality jobs across a dozen states.

For the rest of the article, click here.

Sometime next month we're going to be pouring a large concrete transfer slab at the second floor of One Delisle. Its function is to take the loads coming down from the entire tower above it and "transfer" them onto new structural elements, before being brought down to our mat foundation at the bottom of the parking garage.

Put differently -- and, as always, I should warn you that I'm not a structural engineer -- a transfer is used whenever you have a change in your structural grid and the loads don't have a straight path down to your foundations. Because whenever this happens, you're now introducing moment forces and those need to be dealt with structurally.

Transfer slabs are relatively common here in Toronto (which isn't the case in every market), but they are expensive and they consume a lot of depth. In the case of One Delisle, our level two transfer slab is 1.8 meters deep and it's going to contain about 1,200 m3 of concrete. (Some of you might also recall that One Delisle's mat foundation is over 4m deep.)

We were reviewing this with the team today and we think that we'll be able to pour about 100 m3 of concrete per hour. That means that this slab will take about 12 hours to pour! This requires a lot of coordination. Neighbors need to be notified, pumps need to be on standby in case of a breakdown, and so on.

Another major consideration is heat. When concrete cures it generates a lot of it. And with a thick slab like this one, I am told that we run the risk of the middle starting to overheat (especially with the hot weather that we've been having lately). The guideline limit is 60 degrees Celsius, so we'll be monitoring it for probably about 1-2 weeks following the pour.

I find these details fascinating. Maybe some of you do too. So once it's poured, I'll share a few photos.

If I were to make a broad generalization for the way that we typically design the structural systems for residential buildings and office buildings here in Toronto it would be as follows: office buildings tend to have a big structural core with perimeter columns and residential buildings tend to have a smaller core accompanied by both columns and shear walls (long structural walls essentially). There are a myriad of other differences, but for the purposes of this post, I'm going to run with this broad classification.

When something is typically done a certain way it often means that it is generally what the market wants and it is a cost effective solution. In the case of office buildings, this sort of structural system is essential for maintaining open plans and future flexibility. You can't have shear walls interrupting your floor plates. And because big office buildings also tend to have a lot of elevators, the structural core is usually what provides lateral stability to the building (or at least this is what the structural engineers tell me).

But this same imperative for open plans isn't usually there for residential buildings. In this case, the unit demising is often fairly fixed and the individual resident/tenant spaces tend to be smaller than in office buildings, which makes frequent structural elements a lot more palatable. And since the elevator cores also tend to be smaller (fewer elevators), there is usually a need to introduce other structural elements that can provide the building with lateral stability. (Again, this is what the engineers tell me.) So enter all the shear walls.

But every now and then, somebody in Toronto will ask: Is this the right way to be building? Other cities don't build their residential buildings with all of these shear walls and so should we really be limiting the future flexibility of our multi-family housing supply by constructing in this way? These are good questions. The short answer is that it tends to be easier/cheaper to build this way. Our market is used to it. And generally end-users are just fine with it.

However, this method of building isn't necessarily a universal truth. The structural system for One Delisle, for example, is far closer to that of an office building than it is to that of a typical residential tower. Much of this was driven by the building's architecture and its continually changing floor plates. I have also heard of instances where purpose-built rental developers are choosing to go column over shear wall so that there's greater flexibility in the future. There's certainly a case to be made for this.

As developers, it is impossible to know all there is to know about any one discipline. You need the right team in place for that. But we do have to look at the bigger picture, weigh all of the constraints, and then hopefully make a reasonably good decision. This is one example of that.

Image: Bay-Adelaide Centre North, Toronto