By rough order of magnitude I don't see how this is any more than a fun fact with no commercial relevance. 4 billion tonnes of concrete are used annually and only 10 million tonnes of coffee. Even if you could gather up all of the grounds you'd still barely put a dent in the concrete production.
Unless the strength benefits result in lighter structures using less concrete. Though I suspect a lot of the use of concrete require the dead weight of concrete more than the strength (think of a gravity dam for example).
But I think the idea was more about what to do with the 10 million tonnes of coffee to help the environment than how to replace 2 or 3 billion tonnes of filler necessary to create concrete.
I guess that is another way of looking at it. However, with the pyrolysis step and the cost of collection I still don't see how it helps. A busy coffee shop produce perhaps 10kg of waste a day and the big players already have ways of recycling it.
Unless the strength benefits result in lighter structures using less concrete. Though I suspect a lot of the use of concrete require the dead weight of concrete more than the strength (think of a gravity dam for example).