Thursday, January 23, 2020

Concrete That Can Reproduce

A new type of concrete is under development -- a concrete that is said to be "alive." Not alive in the usual sense, but alive in that it is able to reproduce.

This concrete is being researched at the University of Colorado, Boulder by an interdisciplinary team using cyanobacteria, microbes that use photosynthesis to capture energy and use that energy to absorb carbon dioxide from the air, turning the sand in the mix into calcium carbonate, or cement. The trial mixture is water, sand, nutrients, cyanobacteria and gelatin (which seems to help the matrix built by the bacteria).

Experimental blocks reached maximum strength over a few days, but even after several weeks they were still alive and were able to spawn new blocks when put in molds with new ingredients. The potential advantage of this system is that it does not use Portland cement, and is not fussy about the type of sand it uses: it could even be recycled glass or recycled concrete. There are really positive environmental implications.

Funding for the project was through Darpa, the US Department of Defense's speculative research arm.

Friday, May 20, 2016

Concrete That Glows in the Dark

(Photo : Investigación y Desarrollo)
There has been an amazing development in the field of concrete. A concrete currently under development has the ability to glow in the dark. During the day it absorbs energy from the sun and is able to emit light during the night for up to 12 hours. The research is underway at Mexico’s Michoacan’s University of San Nicolas Hidalgo.

Whether or not this material is bright enough that it could be used to replace street lighting remains to be seen, but the possibilities for creative uses are really exciting. Imagine sculptures made from this material! Or if it scales down, jewellery!

José Carlos Rubio, a professor at the University, is the product’s inventor. It has been nine years of research and development and is currently being commercialized.

When water is added to Portland cement powder, crystals form that block light making the resulting concrete opaque. Apparently Rubio has discovered a method to make those crystals transparent, enabling sunlight to penetrate. It is not clear what material has been added to make the concrete phosphorescent, but it is not a plastic that will break down over time. The professor claims that the phosphorescence should last for 100 years.

Sunday, September 14, 2014

Ageing Concrete

Concrete rubble breakwall

A ten minute bike ride from my studio there is a concrete breakwall that keeps Georgian Bay waves away from a small boat launch. This blog isn't about concrete construction, but the surfaces of these huge blocks made me rethink how I see concrete.

When concrete is formed and when it sets, it looks like concrete. There is no mistaking it for another material, although some sculptors change the surface to make it look more like stone. Some even use metallic pigments to make it look like metal. But it is what it is and from my point of view, that's the way it should be. Concrete is a simple and honest material. Leave it alone. Look at Tadao Ando's concrete to see what I mean.

But I think my opinions are changing. Seeing these massive broken concrete slabs above and below the water made me realize that what you are actually making is a kind of stone. Portland cement, the "glue" in concrete, is made by super-heating limestone or chalk to release the water that is chemically combined in it, and when water is added back to it it actually becomes a stone once again binding other aggregates together. These old blocks at the water's edge now have surfaces rich with lichens, mosses and even small growing plants -- just like the natural limestone outcroppings in this area. The edges are worn from being moved around, some have cracked from ice and frost damage. They have a history, like the glacier-moved boulders we see in farmer's fields in Southern Ontario, only these old concrete slabs have their surfaces marked by people, machinery, and a shorter time span. Concrete is a man-made material, but give it enough time and it becomes more and more like what it came from.

Thursday, September 4, 2014


As the author of Concrete Handbook for Artists and a large website about concrete I get asked a lot of questions in response to specific problems about small scale concrete objects and jewelry. Here are a few of the most frequently asked ones.

1. "Why is my work cracking? I remove it from a mold (or some other process) and a few days later I pick it up and it's cracked/broken." Almost invariably my first response is that you used too much water in the mix. The mix is too wet. For those who have worked in plaster, you must realize this is a completely different material. As a general rule, the LESS water you use, the better. You should be able to form a ball in your hand with the mix and stand it up on the table and it should not slump (or crack apart if it is too dry). It has to be damp, but not wet. Why is this? Doesn't concrete need lots of water to work? No, it only needs enough water to hydrate (chemically combine) with the particles of Portland cement. This is a chemical reaction, not a drying process. Any more than that minimal amount of water  and you are left with tiny spaces in the final product which weakens it.

Next, you have to keep the work covered with plastic sheet for about a week so that all the water you put into it becomes hydrated with the cement, and not allowed to evaporate into the air. If the surface dries before it sets your final product will have a weak surface – read "soft, dusty." If you use too much water the concrete will also shrink more than it should. This can cause cracking as well. You can compensate for this by using lots of fibres (nylon, polypropylene, fibreglass, PVA.) Let the piece cure for at least a week before handling it. You can do surface work before this – carving, filing, adding a slurry to fill holes, etc. – but you must be very careful. Even after that week I like to keep work covered or let it sit underwater for another week or so before sealing.

2. "In jewelry, my concrete has shrunk and pulled away from the walls of the piece." See answer to Number 1 above. Too much water means too much shrinking. Use less water and add fibres.

3. "The surface seems soft, dusty, easy to scratch, even after it's cured for a week." I hate to repeat myself, but too-much-water is the probable cause.

4. "Where can I buy metakaolin? You talk about it all the time and I can't find less than a 50 pound bag?" Luckily there is now someone on Etsy selling smaller quantities. You can buy as little as two pounds. Unfortunately they only sell it if you are in the United States. Considering this is a white powder in a bag, you can see why they don't want it crossing any international borders.

This Etsy shop quotes a concrete recipe from the Ganoksin Project. I thought it sounded familiar; then I realized I had written that Ganoksin article several years ago. Things come full circle...

5. Last question for this blog entry. "When I pull the object from the mold it is covered with (tiny/large) holes. What's happening?" Concrete contractors call these worm holes. They are from air bubbles in the mix. Depending on the type of mold, you need to vibrate the mix somehow so the bubbles float away from the surface of the mold. Large scale you can rent a concrete vibrator. Small scale you can tap the mold with a stick or a small hammer, all around the mold walls. You can also use an electric palm sander, and let the vibrating surface sit on sections of the mold wall. On the jewellery scale I use a vibrating engraver and hold the tip against sections of the mold. You will see the concrete slightly liquify as you do this. Do not do it excessively or the solids in the mix will start to separate and sink.
 You also should try using a mold release agent. There are commercial ones available, some in a spray can, or you can make your own. There are various recipes on the internet, but they are usually oil-based and easy to make. Try to put them on in as thin a layer as possible.

Sunday, September 1, 2013

Concrete Lamps

It's always exciting to see  concrete being used in a way you least expect it.  You normally think of lighting as, well... "light." Itai Bar-on is an Israeli company that has introduced a line of concrete lamps called the Bullet Collection. 

Photo credit Yael Engelhart

The light is diffused through a Perspex  (acrylic) plate and they are available in a variety of different tints such as orange, blue or grey. Their web site explains that is was a collaboration between Itai Bar-on and Oded Webman, a Tel-Aviv based designer.

Their free-form concrete tiles are also worth checking out.


Wednesday, August 7, 2013

Hard Goods: Concrete Furniture

Hard Goods make lovely concrete and steel chairs. They don't reveal the concrete mix that enables them to be so thin, but Design Milk mentions it is an "engineered concrete". This is usually code for adding pozzolans and fibres and balancing everything perfectly. 

No. 002 Modern Muskoka Chair

The owner of Hard Goods, Brandon Gore, has a great statement about cost and quality on his own website

“As with all things in life, you get what you pay for. My price is a direct reflection of the quality of work I produce. If budget is your deciding factor, then I am absolutely not the right person for you. I am not the WalMart of craftsmanship. However, if you value expertise, distinction, and knowing that you bought the best, then I’m the craftsman you’ve been looking for.” I couldn't agree more.

                                Thanks to for their article here.

Friday, August 17, 2012

Jo Woffinden Concrete Sculptures

Jo Woffinden is a London-based artist who works in concrete, but has a background in ceramics. Her recent forms are based on curves and planes:

"My current work synthesizes elements taken from contemporary architecture with the underlying currents, which unfold Baroque structures. I have used the curve to create a spatial flow between planes and lines, which disrupt and work with simple geometry. Through subtle tensions, I intend to create a relationship between surfaces and forms, which can alter our perception of space."

Describing her concrete work she says:

 "Using concrete I have developed tactile surfaces, which appeal to the senses. I intend to show concrete as soft, warm and inviting and for the material to act as mediator between interior and exterior.  I would like to invite the viewer to engage with space and materiality in new ways through their encounter with my sculptural objects.

You can see more of Woffinden's work on her web site: