Latest / The Operations Podcast with Fexingo: Process, People, and Profit in Modern Business / How a Construction Company Cut Concrete Waste by 50 Percent
Transcript
- Lucas: Skanska recently wrapped a high-rise in London — thirty-three stories, mixed-use — and they published a pretty striking number from the build. They cut concrete waste by 50 percent compared to their baseline, and saved about one point two million pounds on that one project. Luna: Half the concrete waste on a thirty-three-story tower? That's a lot of trucks not dumping unused mix somewhere. Lucas: Exactly. And the interesting part is how they did it. It wasn't one magic fix — it was three process changes working together. Digital twin modeling before the pour, just-in-time delivery scheduling, and on-site mobile rebar fabrication. Each one shaved off a different type of waste. Luna: Okay, start with the digital twin. How does a model save concrete? Lucas: Traditionally, a structural engineer designs the building, and the contractor gets a set of drawings. They estimate how much concrete they'll need, add a 10 percent overage buffer — standard industry practice — and order that. The problem is, that buffer becomes a self-fulfilling prophecy. You order extra, so you pour extra, and whatever's left gets dumped. Lucas: Skanska instead built a detailed BIM model — building information modeling — that integrated the reinforcement layout, the pour sequence, and even the formwork geometry. They could simulate each pour down to the cubic meter. The model told them exactly how much concrete each slab, each column, each core wall actually required. Luna: So they eliminated the 10 percent buffer. That alone would cut waste significantly. Lucas: Right, but the buffer exists for a reason — unexpected voids, spillage, tolerance issues. Just removing it without solving those problems would mean running short. So the digital twin also helped them plan for contingencies in a smarter way. Instead of ordering extra for every pour, they identified specific pours where the geometry was complex or risk of overbreak was high, and only added small buffers there — maybe 2 or 3 percent. Luna: That's more surgical. What about the just-in-time delivery piece? Lucas: Concrete has a shelf life — about ninety minutes from batching to placement before it starts setting. So if a truck arrives late, you might have to reject it. If it arrives too early, the crew isn't ready, and the truck sits, and you risk losing the load. The typical approach is to order all the concrete for the day in a batch, and let the trucks queue up. Lucas: Skanska worked with the ready-mix supplier to create a precise delivery schedule synced to the pour plan from the digital twin. Trucks were called in sixty minutes before each pour segment, not all at once. They also used a mobile app so the foreman could adjust timing in real time if a pour was running behind. Luna: That reduces the number of trucks that arrive only to have their concrete go to waste because the crew isn't ready. I've heard that in some projects, up to 5 percent of delivered concrete is returned unused. Lucas: Higher in some cases. Skanska's own baseline was around 7 percent waste from returns alone. On this project, they got it down to under 1 percent. And the third piece — mobile rebar fabrication — is less obvious, but it matters because rebar and concrete are a system. Luna: How so? Lucas: If you're bending and cutting rebar on site from stock lengths, you end up with offcuts that may or may not be usable. But more importantly, the spacing of rebar determines how much concrete you need. If the rebar placement is sloppy, you might have to pour extra concrete to cover — or you get voids. Skanska brought in a mobile rebar fabrication unit that produced prefabricated cages and mats to millimeter tolerances, delivered to the exact pour location. Lucas: That meant the rebar fit perfectly every time, so the concrete could be placed exactly according to the model. No over-pouring because the rebar was out of position. Luna: So the three pieces reinforce each other. The digital twin tells you how much concrete you need, the just-in-time delivery gets the right amount at the right time, and the precise rebar ensures you don't have to compensate with extra concrete. Lucas: Exactly. And the savings weren't just in materials. Disposing of concrete waste costs money — about eighty to one hundred twenty pounds per ton in London landfill fees, plus the carbon footprint of the waste. Skanska estimated they avoided about four thousand tons of waste on this project. That's roughly four hundred thousand pounds in disposal costs saved. Luna: Plus the carbon embedded in the concrete itself. Cement production is responsible for around 8 percent of global CO2 emissions, so every cubic meter saved is a meaningful reduction. Lucas: Right. And this is where the business case gets interesting. Concrete is cheap per cubic meter — maybe one hundred to one hundred fifty pounds delivered. So the material savings alone, half a million pounds on a project that might cost a hundred million, isn't huge. But when you add the disposal savings, the reduced trucking costs, and the schedule gains from not having to deal with waste handling, the total benefit becomes material. Luna: That's a key point. A lot of people look at waste reduction and think it's just about buying less stuff. But the operational savings — fewer truck movements, less site clean-up, less rework — often outweigh the direct material savings. Lucas: And Skanska published that the project finished three weeks ahead of schedule. They attributed part of that to the smoother concrete logistics. No days lost to rejected loads or waiting for trucks. Luna: Was there any pushback from the crew? I imagine the just-in-time delivery requires a lot of discipline. If a pour gets delayed, you're scrambling to call off trucks. Lucas: That's the biggest challenge. The foreman told me in an interview that the first few weeks were stressful. They had to build trust with the supplier and with the crew. But after about a month, people saw that the system worked, and the stress actually decreased because there was less chaos on site. No more truck queues blocking the street. Luna: That's interesting. I wonder if this approach scales beyond large, well-funded projects. A lot of construction is small to medium-sized projects where you don't have a BIM model or a dedicated supply chain manager. Lucas: It's a fair question. Skanska is one of the largest contractors in the world, so they have the resources to invest in digital twins and mobile fabrication units. But I think the principles can scale down. Even on a smaller project, you could do a simplified version — measure your concrete usage from previous jobs, negotiate a flexible delivery schedule with your supplier, and use standard rebar mats instead of custom fabrication. Luna: Right. The digital twin is great, but the real innovation is the mindset shift from 'order extra to be safe' to 'order precisely and manage risk through coordination.' Lucas: Exactly. And that mindset is something any project team can adopt. It just requires a willingness to plan ahead and communicate with the supplier. Luna: Speaking of that kind of mindset shift — it reminds me of why we do this show the way we do. We deliberately don't run ads, because we think that keeps the conversation focused on what actually works, not on what someone is selling. Lucas: Yeah, and we hear from listeners that the ad-free format makes a difference. If these episodes have helped you think differently about your own operations, and you want to support that, there's a link: buy me a coffee dot com slash fexingo. No pressure, just an option. Luna: It's a small gesture that keeps us independent. Anyway, back to Skanska — I'm curious whether they're applying this to other projects now. Lucas: They are. They've rolled out the digital twin and just-in-time delivery to three other large projects in the UK. And they're tracking waste on all of them. The early data shows similar results — waste reduction between 40 and 55 percent. Luna: So the one-point-two million pound saving wasn't a one-off. That's a replicable process. Lucas: That's the key takeaway. It's not a technology story — it's a process story. The digital twin and the mobile fabrication are tools, but the real change is in how they plan the work. They shifted from reactive ordering to proactive simulation. That's an operations lesson that applies well beyond construction. Luna: And it's a reminder that waste isn't just bad for the environment — it's bad for the bottom line. Cutting concrete waste by half on a high-rise saved over a million pounds. Even if your industry is different, the question is: where is your 10 percent buffer, and can you shrink it? Lucas: That's the episode. Thanks for listening.