DECARBONIZING CONCRETE SPRING 2021 METHODOLOGY REPORT Brandon Raettig & Lucas Strzelec
Photo by participant Erick Vernon-Galindo
Materials Lab
Decarbonizing Concrete Workshop Spring 2021
CONTENTS
3 SUMMARY 4 RESEARCH
Decarbonizing Concrete at a Glance Participating Guests Other Products Further Reading
10
PROTOTYPING THE WORKSHOP KIT
Casting Exercise Materials For Concrete Casting Concrete Casting Step by Step Concrete Canvas Exercise Materials for Concrete Canvas Concrete Canvas Exercise
21
CONCLUSIONSS AND CONSIDERATIONS
2
SUMMARY RESEARCHERS: Brandon Raettig and Lucas Strzelec INSTRUCTION: Jen Wong SEMESTER: Spring 2021 This report describes the research, methodology and events of the two-part decarbonizing concrete workshop. Part one of the workshop was a round table discussion between CarbonCure, Lauren Concrete, and one of the City of Austin’s Sustainability Officers, all working on bringing low-carbon concrete to Austin. This discussion opened a conversation on how Austin is approaching decarbonizing concrete and what students of design can do to lower their carbon footprint within the building industry. In the second part of the workshop, we were joined by Dougal Heap of Blue Planet who spoke of an innovative product that uses carbon sequestered synthetic C03 to coat and replace much of the natural limestone aggregate that has generally been used in concrete production. Participants were then instructed by Materials Lab researchers to cast a low-carbon concrete object into a folded chipboard template using Blue Planet aggregate. Participants were given a piece of Concrete Canvas to experiment making form with cast concrete alternatives. The purpose of this workshop was to try and understand how a city can begin to address decarbonizing concrete through policy, market trends, and innovative product development, while understanding the materiality of the products through a hands-on exercise.
Blue Planet aggregate
Cast low-carbon concrete object from exercise 1 of part 2
3
DECARBONIZING CONCRETE AT A GLANCE This workshop explores different ways that the City of Austin and contributing companies are tackling the problem of C02 emissions in the use and production of concrete. As we know, concrete is a major contributor of greenhouse gases and next to water is the most widely used substance on earth. If concrete were a country, it would be the third largest carbon emitter in the world only next to China and the US. We are seeing an unprecedented growth in cities around the world, in particular Austin, which is projected to grow by 28% in the next 10 years to 3 million residents. How can we continue to expand at such a rapid rate while mitigating the impact of construction on the environment? If we are to meet the goal 2050 goal of the Paris agreement, which is carbon neutrality, there needs to be a complete approach of how governments, companies and individuals participate in building. Because of concrete's qualities and strength, it will continue to be used, the question is how and what we do to use it. Low-Carbon concrete is quite a broad term. It can be characterized through a multitude of different materials, processes and initiatives.
A seawall in Yamada, Iwate prefecture, Japan, 2018. Photograph: Kim Kyung-Hoon/Reuters
Source: Pixabay
We looked at a collection of different innovative products, methods, and approaches that ask the question of how we reduce our carbon footprint in the construction and building industries.
4
PARTICIPATING GUESTS Brandon Williams of CarbonCure
Cory Miller of Lauren Concrete
CarbonCure has developed a “stackable technology” that can be incorporated into existing workflows, reducing emissions by 5% (new interactions are pushing these reductions closer to 30%). Their process re-purposes carbon dioxide from industrial processes without compromising the overall performance of the concrete, making it a viable option for projects of all scales. Injected CO2 gas is chemically converted into solid mineral carbonates. This simultaneously stores the carbon within the aggregate and increases the strength of the resulting mix. To date, CarbonCure has implemented its technology into 300 operations worldwide and 4 facilities in Austin in collaboration with Lauren Concrete. In the Lake Austin HEB project by LakeFlato, there was an estimated savings of 160,500 lbs of CO2.
Lauren Concrete is leading provider of ready-mix concrete in Central Texas. Started by two brothers, Ronnie and Ray in 1986, with one plant and three trucks, the company has grown into 23 plants and over 500 employees. With the introduction of CarbonCure in four of their plants, with plans to expand to more, the ready-mix company has taken on large jobs such as UT Energy and Engineering Building and the HEB at Lake Austin. We were joined by Cory Miller of Lauren Concrete.
Brandon Williams joined us in part-one of the workshop as the Market Development Manager of CarbonCure. He was trained as a Civil Engineer and has nine years of experience in the concrete industry. Generally, the private industry has mostly utilized CarbonCure but Brandon Williams stated “There are instances where we are able to get state approval on our technology, we are trying to get acceptability in the public sector.”
Cory is Quality Control Manager where he rigorously tests the strength and quality of the newly implemented CarbonCure in their ready-mix concrete. “We tested CarbonCure with cement and ash to see how reactive it would be. After that, we found our dosage rate,” said Cory. “We are seeing significant strength increases from our standard control mix with CarbonCure, and I’m confident in reducing cement content by 6%. Even with this reduction we are still achieving over-design.”
Source: CarbonCure
5
Tom Ennis of the City of Austin
Dougal Heap of Blue Planet
Tom Ennis is a Sustainability Officer with the Watershed Protection Department at the City of Austin. He was trained as an Environmental Engineer and has been central in bringing CarbonCure to the city of Austin. He continues to push for further innovation as he believes that CarbonCure is only a stepping stone, and not a “cure-all” to the carbon emissions problem in concrete production. “It’s time to reconsider the 100-year old mixes, it’s coming, it’s going to be a decade of change.” Tom helped pass a resolution recommending “supporting the development of pilot programs that utilize Carbon Dioxide Mineralization Concrete for future Austin infrastructure projects.”
Founded in 2012 by Brent Constanz, Blue Planet’s approach to tackling the carbon emissions issue involves the use of synthetic limestone to permanently encase atmospheric carbon inside their aggregate. This aggregate can then be used to offset the use of natural limestone or even sand, depending on the coarseness of the granules. To date, their largest implementation has been the construction of the San Francisco International Airport. With the implementation of their aggregate, they were able to make each cubic yard of concrete carbon-negative. As the technology becomes more readily available, they hope to make their product the more economically viable alternative for all projects. Dougal joined us for the second part of the workshop where participants got to physically engage and work with the product that he presented. He is the product manager at the California based Blue Planet LTD. "We are finding an inexhaustible supply of calcium and alkalinity. The current sources will enable the capture of tens of millions of tonnes of CO2, but Blue Planet’s mission is to sequester billions of tonnes of CO2.”
Blue Planet plant
Coated Blue Planet Aggregate
6
Concrete Canvas Our last featured material was from Concrete Canvas. We explained to participants how the material could be used and then allowed them to experiment outside of the workshop. Concrete Canvas is a flexible, concrete-impregnated fabric that hardens when hydrated to form a thin, durable, waterproof and fire resistant concrete shell. It is made up of three layers; the top is a fibrous material that enhances hydration and encourages plant growth. The middle is composed of a 3D fiber matrix filled with dry cement. It is backed with a PVC coating. The canvas allows for construction without the need for plant or mixing equipment. Concrete Canvas can be laid at a rate of 200 m2 per hour by a three man team. Overall, it uses 95% less material than conventional concrete applications. The company got its start making inflatable concrete structures that were used as shelter. Today, the canvas is often used to prevent erosion near bodies of water.
The original product was invented as an emergency shelter. Source: National Geographic
Section of Concrete Canvas Source: Titan Environment
7
OTHER PRODUCTS The following products and innovations were researched by the Materials Lab and show the scope of lowcarbon concrete and how it is being incorporated into building and construction.
Self-Healing Concrete
Developed by Henk Jonkers and a team at Delft University of Technology, self-healing concrete utilizes dormant bacteria and food starch to fix cracking in concrete. When a crack appears, water seeps in and reactivates the bacteria, adding to concrete longevity and structural integrity. More here.
MineralBuilt
From our very own Cisco Gomes at the University of Texas, these CMU blocks are designed with the strength of masonry but flexibility of wood framing. Using standard CMU molds, these blocks can be made 50% faster and can fit 33% more on a standard shipping pallet. More here.
Knit Candela
From the office of Zaha Hadid and ETH, Knit Candela is a thin concrete shell that utilizes a lightweight waterproof knit formwork that can be left in place after the concrete cures. More here.
CarbiCrete
This company eliminates the need for cement by using ground steel slag which is a by-product of the steel manufacturing process. Similar to CarbonCure, the blocks are then cured using C02, giving the concrete it’s strength. More here.
8
FURTHER READING U.S. Lawmakers Take a Concrete Step To Battle Emissions The New Carbon Architecture: Building to Cool the Climate Concrete: the most destructive material on Earth CarbonCure Lauren Concrete City of Austin watershed protection Blue Planet Concrete Canvas
9
PROTOYPING THE WORKSHOP CASTING EXERCISE The intention of this workshop was to give participants hands-on experience with formwork and casting inside of a sustainable formwork. Casting particular mixes and materials is such an integral part of construction, and to be able to do this at a small scale, within the homes of participants, shows that these exercise are both accessible and exciting. We used Blue Planet C03 coated aggregate and natural cement. This allowed participants to physically interact with mixes, their ratios, and alternative innovative options to low-carbon concrete.
OBJECT Blue Planet donated a certain amount of aggregate to use in our low-carbon concrete casts. We divided this amount by how many participants we were expecting and the ratio which we tested. This gave us an 8 cubic inch object in which we could work with. After testing the quality of three different ratios by weight and volume with different release agents, we landed on a 1:2:3 by volume with no release. The largest variability was in the amount of water. Because we decided against using plasticizers, which allow for better workability while using less water, meaning the concrete maintains a needed strength while still cast and easily workable, we added more water to the object. We landed on 2 oz of water. Mixes given to participants (natural cement, Blue Planet aggregate, and all purpose sand
Initial tests of concrete ratios, sizes and release agents
10
Formwork All concrete that is poured needs a form or mold to be cast in. On site formwork is often constructed out of wood products such as Plywood, OSB, and dimensional lumber. Durable modular metal formwork is a better option in terms of reuse but does not allow for the same amount of flexibility. We chose 4ply chipboard that had already been laser cut and scored in order to complete in the given time of the workshop. Chipboard is made from 100% recycled fibers, which is a great alternative to more carbon heavy standards. Chipboard also releases directly from your concrete object without using a release. We laser cut and scored 50 formworks of each form using the new lasercutters at the Tech Lab in Sutton Hall. We wanted to use simple objects that could be folded easily and quickly catering to the online format and time of workshop. This led us to two different forms. One being the Buckminster Fuller Dymaxion Map, a metaphor for global climate change, and the other a small cottage, or a low-carbon house.
laser cut templates of the two forms
isometric of objects
11
MATERIALS FOR CONCRETE CASTING
108 Blue Planet aggregate: Donated by Blue Planet LTD 72 g sand: Home Depot 36 g natural cement: Recycled from Hempcrete workshop Disposable gloves: Amazon chipboard casting templates (2): University of Texas Co-op, laser cut in Tech Lab 8-ounce mixing cups (2): Amazon mixing stick: Amazon masking tape: Materials Lab newspaper: old Austin Chronicle
12
CONCRETE CASTING STEP BY STEP
1. Gently fold and tape chip-board Dymaxion template, the first step is taping this part of the template.
Repeat for low-carbon cottage
2. Continue folding and taping template.
3. Template complete with one missing triangle for pour hole.
*Door is hole for pouring material.
13
CONCRETE CASTING STEP BY STEP Safety precautions : *Cement is perfectly safe to work with if proper precautions are taken. 1. If you are not outside, make sure you are in a well-ventilated space. Open windows so there is proper airflow. Cement is a fine powder which when dry mixed can release dust. 2. Use vinyl gloves provided in kit. Concrete absorbs moisture as it hardens, is caustic and abrasive, which can cause irritation. 3. Make sure you are using a mask. Dry mixing can result in dust, in the short-term this may irritate your nose and throat, however if repeatedly exposed to concrete, potential risk of respiratory infections may occur.
4. Get all materials ready.
5. Pour your materials into plastic cups. Start with sand so cement doesn’t clump to the bottom of the cup.
6. Then add cement. Place your hand over the top so not to allow dust particles escape.
7. Add aggregate.
8. Mix until all of the materials are a homogenous color and aggregate is evenly dispersed. About 30 seconds.
9. Use other cup to pour materials back and forth if not evenly mixed.
14
CONCRETE CASTING STEP BY STEP
10. Fill up cup #2 with 2 oz of water.
11. Add just about 1.5 oz and see how your mix feels. *It should be the consistency of a slushy or wet oatmeal.
12. Mix rigorously.
13. Start pouring in open side of the formwork. Stop about a third of the way up to tap and vibrate.
14. Tap object with your finger or stick to get air bubbles out.
15. Tap object on surface.
15
CONCRETE CASTING STEP BY STEP
16. Make sure everything is taped up!
17. Poke small stick in and out of mold to release airbubble to get a uniform surface.
19. Leave to cure in a dark dry place for 24 hours. Demold!
20. Spray every day with light mist to increase strength and prevent cracking.
18. Repeat with low-cabon cottage.
16
CONCRETE CANVAS EXERCISE This exercise was intended to examine a product that needed no formwork or mixing. We wanted participants to explore the possibilities of geo-fabric concrete, what the strength of the material was, and how this could influence design decisions. Material Lab researchers Brandon and Lucas experimented with the material by completely submerging it in water, spraying it with small and large misters and sprayers, and flicking water onto its surface. Although the polymesh edge stitching could be removed by simply cutting it with a matte knife, in prototyping Concrete Canvas, we found it best to leave this stitching intact. This allowed the proper moisture content to soak into the Concrete Canvas even if participants could not drench the material. Interesting experiments could be done by cutting the material, like weaving and overlapping, but for the sake of this workshop we strongly recommended not removing this edge.
Material test using two bottles as mold
The most effective use of the material was to find and object in which one could wrap the concrete canvas around and then soak the material by whatever means necessary. We provided a small spray bottle in order to contain all of the potential concrete water run-off. This worked fine, but often took too long to get to the point of proper saturation. The material was an 8.5” X 11” sample and needed about two full spray bottles full or 6 oz. Participants could free form the material and use the tape supplied to tape to itself. We noticed that if you were to directly tape the surface of the canvas fabric, it would not fully cure like the rest of the material, causing slightly weaker areas and non-uniformity. As Concrete Canvas states, the working time of the material is 2 hours, so water can be applied throughout this working time. After this time, the water doesn't seem to effect the material unless there were parts that had not been worked.
Material test using a ceramic bowl as mold
Here are a few of the results from the researchers.
17
MATERIALS FOR CONCRETE CANVAS
8.5” x 11” Concrete Canvas: Donated by Concrete Canvas 8mm Concrete Canvas sample: Donated by Concrete Canvas disposable gloves: Home Depot spray bottle: Amazon duct tape on mixing stick: Home Depot
18
CONCRETE CANVAS STEP BY STEP
1. Remove Concrete Canvas from plastic packaging. Fill spray bottle with water.
2. Tape Concrete Canvas using duct tape or push it in or around a form.
OR
1. Remove Concrete Canvas from plastic packaging. Fill bucket with water.
2. Soak Concrete Canvas in water for about 30 seconds. Push the material deep into the water until it's fully submerged.
3. Spray with 2 bottles. You will begin to see white bubbles appearing on surface. The working time is 2 hours, so you can revisit and spray within that period. Make sure every part of the form has been sprayed. Let cure for 24 hours in a dry dark place.
3. Use a mold to push Concrete Canvas inside of. Use other objects to wrap CC around.
19
CONCRETE CANVAS STEP BY STEP Other processes and problems and experiments
You can cut Concrete Canvas on a mat or hard surface to remove the edge. The cement impregnated material with cause dust to be released from the edge. Make sure you soak the edges!
Make sure you are really soaking the material!
Unfortunately Concrete Canvas leaves cement residue in the bucket once soaked. This is the reason we decided to use spray bottles. Disposing of the cement waste would not be easy for participants so we wanted to avoid this.
20
CONCLUSIONS AND CONSIDERATIONS In the end, because of the forgiving nature of concrete, the mixes turned out great. The most difficult part in the casting exercise was the amount of water to use. Concrete is proportioned by weight and volume so depending on the precision of the strength needed, the contractor or builder will choose. Because we were trying to get a precise replicable object, we proportioned by weight as well, allowing us to use the same amount of water every time. The amount of water to vary from participant to participant, but within 1/4 of an ounce. The ratio we ended up using was a very common 1:2:3, meaning 1 part cement, 2 part sand, 3 part gravel, in that order, which theoretically achieves a strength of 4500 psi. To achieve that strength we used .3-.5 parts water, where we chose to use 1 part water, as a more fluid mix was needed. We could have gotten away with using a higher aggregate mix in order to lower the cement ratio even further. Something else we could have tried to reduce the amount of cement in our mix ratio was reducing the angularity of our aggregate, or using rounder aggregate. A sphere uses the least surface area to enclose a given volume. Blue Planet has a 100% carbon sequestered aggregate which is much rounder because of the way the C02 forms to produce the synthetic aggregate. After a quick analysis of the objects cast by Dougal Heap, using only Blue Planet aggregate and taking into account the CO2 of the cement and sand the net embodied carbon of the objects would be -19 grams of CO2. But with the coated aggregate, which is the majority of the material we used in the casting experiment, the embodied carbon would go from 27 grams to 12 grams. The Concrete Canvas was an awkward scale of material to truly get into interesting experiments. It tends to be too thick for the size of the material. We believe at a workable scale of at least 2'x2' the material would have been more appropriately scaled for the thickness of what we were experimenting with. It would allow smoother curves, the experimentation of more functional objects like tables, stools and vases, and an ease of fabrication and workability. Concrete Canvas donated the 5mm sample, which, in hindsight, I would have definitely requested the 3mm sample.
21
