While paging through the feed a few days ago our attention was caught by something a little away from the ordinary in Hackaday terms, a DIY video about creating cast concrete signage from [Proper DIY] which we’ve placed below the break. A deceptively easy-looking mould-making process has a few tricks that will make the difference between a hard-wearing sign that lasts for years, and a lump of concrete.
So, to make a cast concrete sign, you throw together a mould with some letters, and chuck in some concrete? Not so fast, because the key appears to be preparation, and ensuring that there are no 90-degree corners on the mould parts. The letters are carefully shaped and sealed with varnish before being attached to the mould with silicone adhesive, and all the corners are beveled. Finally a light oil is used as a release agent, and hefty vibration takes care of any air bubbles.
The result is a set of signs, but we can see these techniques finding uses outside signage. For example, how about casting using a 3D printed mould?
Continue reading “Making A Concrete Sign”
Growing up, we got to play with all kinds of things in miniature. Cars, horses, little LEGO houses, the lot. What we didn’t get is a serious education with miniature-sized dams. This recreation of the glorious Hoover Dam from the [Creative Construction Channel] could change all that for the next generation.
The build starts with the excavation of a two-foot long curve in a replica riverbed. A cardboard base is installed in the ditch, and used as a base for vertical steel wires. Next, the arch of the dam is roughed out with more steel wires installed horizontally to create a basic structure. The cardboard is then be removed from the riverbed, with the steel structure remaining. It’s finally time to pour real concrete, with a foundation followed by the main pour into foam formwork. The dam is also given 3D printed outlets that can be opened to allow water to pass through — complete with small gear motors to control them. The structure even gets a little roadway on top for good measure.
The finished product is quite impressive, and even more so when the outlets open up to spill water through. Such a project would be great fun for high school science students, or even engineering undergrads. Who doesn’t want to play with a miniature scale dam, after all? Bonus points if you build an entire LEGO city downstream, only to see it destroyed in a flood.
Continue reading “Miniature Concrete Hoover Dam Is Tiny Engineering Done Right”
Concrete is an incredibly useful and versatile building material on which not only today’s societies, but also the ancient Roman Empire was built. To this day Roman concrete structures can be found in mundane locations such as harbors, but also the Pantheon in Rome, which to this day forms the largest unreinforced concrete dome in existence at 43.3 meters diameter, and is in excellent condition despite being being nearly 1,900 years old.
Even as the Roman Empire fell and receded into what became the Byzantine – also known as the Eastern Roman – Empire and the world around these last remnants of Roman architecture changed and changed again, all of these concrete structures remained despite knowledge of how to construct structures like them being lost to the ages. Perhaps the most astounding thing is that even today our concrete isn’t nearly as durable, despite modern inventions such as reinforcing with rebar.
Reverse-engineering ancient Roman concrete has for decades now been the source of intense study and debate, with a recent paper by Linda M. Seymour and colleagues adding an important clue to the puzzle. Could so-called ‘hot mixing’, with pockets of reactive lime clasts inside the cured concrete provide self-healing properties?
Continue reading “Self-Healing Concrete: What Ancient Roman Concrete Can Teach Us”
Reinforced concrete is the miracle material which made possible so many of the twentieth century’s most iconic structures, but here in this century its environmental footprint makes it something of a concern. As part of addressing this problem, a team at TU Dresden in Germany have completed what is believed to be the world’s first building made with carbon-reinforced concrete, in which the steel rebar is replaced with carbon fiber.
New materials are always of interest here at Hackaday, so it’s worth reading further about the nature of the reinforcement. The carbon fiber is woven into a mesh, or as a composite material that mimics existing rebar structures. These two types of reinforcement can be combined in a composite to produce a concrete structure much lighter than traditional steel-reinforced ones. If you page through the architecture critic description, it’s this lightness which has enabled the curving structure of the Dresden building to be so relatively thin.
The carbon saving comes presumably in the lower energy cost from not smelting iron to make steel, as well as the need for less concrete due to the lightness. All we need now is a low-carbon replacement for Portland cement.
Want to know more about concrete reinforcement? We’ve got you covered.
A good coffee table should have a hard-wearing surface and some serious heft to it. This build from [designcoyxe] hits both those criteria with its concrete-based design.
To create the table surface, the first step was to create a form. Melamine was used for the job, thanks to its smooth surface. A rectangular form was readily fabbed up, sealed internally and waxed, and then the concrete was poured. For added strength, the form was only half-filled, and a mesh was added for reinforcement. The rest of the concrete was then poured in to complete the tabletop. The table legs themselves were crafted out of maple, formerly used as a butcher’s block. The light wood makes a great contrast to the dark grey concrete. Plus, the stout, thick, wooden legs are a great combination with the strength of the tabletop itself.
It’s hard to overstate how good concrete is as a coffee table material. It’s difficult to damage and difficult to stain. Plus, if you really need to drive a point home, you can be certain slamming down your mug will get everyone’s attention (just be wary of injury). We’ve seen some other great concrete furniture before, too.
Continue reading “Concrete Coffee Table Can Take A Beating”
Steel is scarce. Wood is not an option. And you need a boat now. These wartime circumstances drove innovation in all kinds of crazy directions, and one somewhat less crazy direction — concrete boats. As [Peter Sripol] demonstrates in the video below the break, making an RC concrete boat isn’t hard. Making a fast one on the other hand is. But that didn’t stop him from trying, and we think the effort deserves a look.
Starting with a basic displacement style hull, [Peter] and his cohorts experimented with a simple RC boat that worked, but could only move at slow speeds. They turned things up a notch or two and instead modeled their concrete boat after an RC speedboat hull that they had on hand.
The construction methods left a lot to be desired though, and they even tried various wire meshes as rebar, but they proved too heavy. Eventually though, they got a working hull, and had some fun with it. Rather than try to make the hull watertight with a rudder and propeller, they opted for a ducted fan and an airboat style rudder to make what they call the “world’s fastest concrete boat”.
Whether it’s the fastest or not is unconfirmed, but it is fast and actually gets on step fairly nicely. We applaud the exploration of alternative materials and the experimentation with different build methods. If building things with concrete floats your boat, then be sure to check out this concrete pinhole camera.
Continue reading “Concrete Boat Cements Its Way To High Speeds”
Many of the 3D printed houses and structures we’ve seen use concrete and are — frankly — a little underwhelming. Making big squares out of concrete isn’t that hard and while we are sure there is some benefit, it isn’t overwhelming. [Andy Coward] apparently felt the same way and set out to find ways that 3D printing could offer unique benefits in building structures. The result: a beam that would be difficult to create with conventional techniques but is easy to make with a printer. The advantage is that it uses 78% less concrete than a conventional beam with the same properties.
The key is that in a normal beam, not much of the concrete is bearing a significant load. It is simply there because you need some concrete on one side of the beam and then some more on the other side. In the center, surprisingly little of the concrete actually supports anything. The new beam takes advantage of this along with a steel reinforcement at a strategic point. Still, it uses 70% less steel than a typical reinforced beam.
Continue reading “3D Printed Concrete Beam Improves Sustainability”