Reading the comments here, I almost think that there are two classes of people: those of think, and those who don't. I don't quite know what boredom is. Yes, I agree that it takes some mental discipline to keep going on with mental work. I don't disagree that it's easier sometimes not to think than to think. I also don't disagree that all people simply get tired of thinking after a while - after all, we all need a break; mental work is still work. But if most people who, given 15 minutes to themselves, are unable to think and use that productively - that's quite telling. Are they all so seriously tired and worn out that they are all ready to go for a vacation or something? Or can't they think? Perhaps both?

Maybe I'm just skewed by my analytical approach to things, but can't you, you know, solve some problems or something? Don't you have anything to plan for etc.? Myself, I've got a backlog of things I wish to learn, so if you asked me to sit and think for 15 minutes right now, I'd be going through some structural induction proofs I meant to dig through I didn't have time. Or I'd be doing some design work for my home automation system. Or cleaning up some code. I've done a lot of my best programming just laying in bed, in the early morning hours before the alarm sounds. It really helps when you focus on something and keep relevant information immediately available for recall. Or I could be planning the hikes I want to take with the family. Etc.

Environment you're not familiar with? Shit, do they use some cool nanotech on their walls, or is that thing done in a blimp gondola, or in the Himalayas? I'd have thought that most university buildings are like most other university buildings. If you claim lack of familiarity with a room with a desk, what else must you be unfamiliar with?

If you have normal blood sugar levels, then the amount of sugar you consume is irrelevant to your mental performance, unless you posit that somehow the brain itself has a sugar intake integrator and goes hyper when the leaky integrator is past a threshold. Nothing like that has been observed AFAIK. As for caffeine, if I don't get it in the morning, I go right back to sleeping. If I consume it in the evening, nobody cares. I can fall asleep right after going through a 2 liter bottle of cola - not that I do it often, of course.

I don't see how being an extro- or intro-vert has anything to do with the capacity to actually sit down in fucking peace and quiet and think. I start to wonder how anyone achieves anything substantial in this world if they can't deal with 15 minutes of peace and quiet and their own thoughts.

A conduit-shaped opening through a concrete 3D-printed structure could surely be coated from inside with a slick coating before anything is pulled through. All you'd need is to pull a spray head through it. You don't need to embed pipes in concrete.

Chopped fibres aren't the same as long fibres. But I agree that having fibreglass ribbons embedded in the concrete would be a great alternative, as long as long as test coupons would pass relevant tests.

Under watch is OK, but that's not the same as in jail.

Once you have a positioning system (a manipulator) good enough for 3D printing concrete, then adding rebar functionality is peanuts in comparison. Heck, not doing so would be silly, since you should try to leverage the heck out of the expensive manipulator. I personally don't see much housing uses for non-reinforced concrete. As the ground settles, it will crack. Rebar is a relatively cheap fix for that.

Well, if they can solve the problem of rebar, then buckling won't be an issue anymore, since rebar has proper strength from the get-go. I don't really see a slower machine being much better than a fast one. The overall size of the machine depends on what you fabricate, not how fast you go about it (within reasonable limits of concrete pouring).

If I were to make a product out of it, I'd have a 5 axis machine with switchable heads. One head with an extra axis or two that can put out, restrain, cut and spot-weld rebar. Another head that can print concrete. With a 5 axis machine you can trivially print concrete on the surface of rebar going in any orientation. Heck, if they use a mix with fast initial cure, they can do skin/infill just like plastic 3D printers do, except that the infill uses a less viscous mix that self-levels. This could dramatically speed it up, and you wouldn't need to print around every piece of rebar but only some trickier ones.

This could be very much a breakthrough technology, but it would need a bit of capital investment as those machines wouldn't be cheap. For very large constructions, instead of X-Y-Z linear actuators you would need a delta-style arm. Even a big one could be assembled on site and print an entire highway overpass in a week or two, starting with nothing but a hole in the ground.

You're not really seeing 3D printing for what it is. It shouldn't be all that hard to design a printer to deal with vertical rebar. It needs to be a 5 axis machine, but printing concrete on the surface of rebar should be no biggie. Heck, the rebar structure to be printed on can be also "printed" by a machine that can cut, locate and spot-weld rebar. The conduits are plastic only because the usual pouring method needs something to contain the void while the poured concrete is curing. With 3D printing, you just print the voids and you don't need any conduits.

No different from a brick building, really. You can use brick in some places, in some other places you can't. Hopefully here they could use brick :)

You're forgetting buckling, and weak, fresh cement is famous for buckling. Heck, poorly supported brick walls will buckle and collapse during construction because the mortar isn't strong enough -- all the while the same will will stand just fine once the mortar has cured.

This technology eventually can do the whole thing starting with a hole in the ground, all in one go. About the only problem that I see is with the lack of strength of the concrete. They'll do it wrong, it will buckle while it's being printed, and the outcome will be in terms of the number of body bags. I sincerely hope that their printing software keeps a running estimate of the weight of concrete printed, and that their structural people have vetted it.

Here the reviews are a result of a transaction that took place and come from the parties to that transaction, not from random people who just want to vent. Every review has a grain of truth to it - if nothing else than to the state of mind the writer was at the time of reviewing it. Sure, some people get pissed by the littlest of things, and that character trait of a passenger is useful to prospective drivers, for example. So, I'd say that the review system works just fine, you just can't be a doofus when reading the reviews and taking everything at face value.