Tag: concrete

Microsoft Just Invested in a Cement Startup That Turns CO2 Into Literal Building Blocks

There’s hardly anything on this planet that’s more widely in demand than concrete. And while we need the essential building material for infrastructure, housing, and beyond, it comes at a high climate cost.

Production of cement, the glue that holds concrete together, doubled globally between 2003 to 2013, and has since plateaued. Even without rapid growth, its carbon footprint is incredibly significant at around 8 percent of global carbon emissions. Every ton of Portland cement produced—that’s the most common type of cement in construction today—creates nearly the same amount of CO2 emissions.

But big emissions warrant big opportunities. While some companies are working on changing cement itself to reduce its gigantic carbon footprint, California-based Fortera found a different niche.

By creating bolt-on technology that can be fitted to existing cement plants, Fortera can create a cement product made out of reabsorbed CO2 that’s up to 70 percent less carbon intensive than creating traditional Portland cement (even if the plant is powered by less-than-sustainable energy sources). When hooked up to renewable energy, the potential for emissions reduction is even higher.

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“What Fortera is doing is not all that fancy and exotic, but that may actually be part of its secret sauce,” says Andres Clarens, a professor of civil and environmental engineering at the University of Virginia.

A concrete pivot

Fortera was built out of a company called Calera, one of the earliest businesses geared towards green cement. Calera’s process was inspired by how coral mineralizes in the ocean; the company combined seawater with captured CO2 to create calcium carbonate and magnesium carbonate. These materials can double as feedstocks for cement and carbon sequestration, but the company drew early criticism for lack of scalability.

After hundreds of thousands of hours of research, hundreds of millions of dollars of development, and over 100 patents, the economics just didn’t work out. “Unfortunately, while it was great technology, it really just wasn’t grounded in economics,” says Ryan Gilliam, CEO of Fortera. Gilliam was CEO of Calera when it shut down the CO2-to-cement part of the business in 2015. “People thought people would pay for green and that’s what would drive adoption, which is really not how things have happened.”

But it wasn’t entirely a loss, Gilliam says. The technology was already proven, after all. What was really needed was a new mindset. Calera’s goal was to compete with cement producers, creating a greener alternative.

But this second time around, Fortera has pivoted. Their aim isn’t to replace the infrastructure that already exists and supports an industry that creates some 4 billion metric tons of the essential material every year. Instead, it takes what they are already doing and turns the carbon being emitted into something useful. And so far, it’s working—and last year, they began making a test product alongside a small cement plant in Redding, California.

Fortera was also selected in September to receive funding from Microsoft’s Climate Innovation Fund to support building out a full-scale, 400,000 ton-per-year commercial facility, in turn hopefully accelerating the greening of Microsoft’s data center footprint. “Our team was attracted to Fortera’s approach due to its potential for deep emission reductions, competitive cost targets, and its expected compatibility with existing production infrastructure,” Brandon Middaugh, who manages the Climate Innovation Fund program and its strategy at Microsoft, said in a recent press release.

So far to date, Fortera, which is based in San Jose and has a team of around 90 full-time staff, has raised about $150 million and the company is about to kick off another funding round.

The technique

The reason that cement is such a nasty carbon problem is simple: cement’s main feedstock is limestone, which is around 44 percent solid CO2 by weight. That CO2 is lost when the stone begins a process called calcination, producing a double whammy of emissions from the rock itself and the burning of fuel to power the process. “It’s a costly inefficiency that makes no sense,” says Tiziana Vanorio, associate professor in the earth and planetary sciences department at Stanford University.

Fortera’s technology captures the CO2 coming out of the kiln when the lime is being produced. That is used to create a reactive calcium carbonate polymorph, also known as vaterite, or what they’ve dubbed ReAct. Teaming up with Fortera means cement plants get to keep the same limestone feedstocks, use the same infrastructure already in place, but get more out of the same amount of initial material. It keeps costs low for Fortera too, says Gilliam. The plant’s in-house team operates the technology, and the plant’s sales and logistics team help put the product to market.

“[Cement companies] know how to build big plants, run them efficiently, and put products to market,” he says. “So bolting our technology to them, but leveraging what they know how to do really well, is the way to really push the economics where you don’t need a green premium or a value on CO2 to be competitive in the market.”

One product their technology creates, ReAct Pure, made with 100 percent of the low-carbon vaterite, is currently being tested as a full replacement of cement in concrete mixes. But it is available now for other uses in the construction industry.

ReAct Blend, meanwhile, is a mix of the ReAct product and traditional cement and could have several uses, including as a regular cement replacement. ReAct Blend was approved by ASTM International to meet standards for to be blended in with three different categories of cement and concrete, and is already out in the world in a few locations, including in a STEM building at Simpson University and an entrance and staircase of a renovated building at UC Berkeley, resulting in a small-to-moderate amount of carbon reductions compared to a fully-Portland cement build.

Now, Gilliam says, it’s just a matter of scaling up, and with a partnership with lime producer Graymont announced over the summer, there’s a whole pipeline of commercial plants on the way. “Now it’s basically putting shovels in the ground and executing building out that first full commercial plant,” he says.

“I hear regularly that the industry is risk averse, they will never adopt something new, they won’t adopt new products,” he says. “I fundamentally don’t agree with that. I think the industry has always shown that if it’s economic, they will adopt it.”

Sara Kiley Watson

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October 23, 2025
DIY Hopscotch Stepping Stones for the Garden
If you have a little one who loves to explore the garden, these hopscotch stepping stones are the perfect playful addition. They’re easy to make for your first foray into DIY concrete, so let me show you how to make your own!

These hopscotch stepping stones aren’t the traditional children’s hopping game, nor are they typical for a garden pathway. I created these as part of the play garden design I have been developing since my son was born.

The idea behind the play garden is to create a space that is engaging for children while being aesthetically pleasing for grown-ups. I plan to show off the pieces that I’m working on along the way, starting with these hopscotch stepping stones.

Making numbered hopscotch stepping stones is fairly simple and can be done in one afternoon. Let me show you how!

This post will cover…

I made the numbers out of small pebbles and stones.

How to Make Hopscotch Stepping Stones

Make sure to choose a sunny day to work on this project. Keep in mind that the concrete will require 24 hours to fully harden, so make sure to account for this time in your plans.

Materials

(Makes 10 stepping stones numbered 1-9 and a dragonfly)

Most of these materials you can easily get at your local hardware store.

Make It!

First of all, let’s talk safety. Concrete is toxic to skin and can be corrosive. No matter how ‘tough’ you are, just protect your hands with gloves. I know they aren’t fun to work with, but stay healthy, folks. Also, please use safety gear to protect your eyes and ears when using power tools. You only get four of them!

Cut the concrete form into 10 2-inch-thick moulds by using a handsaw or a handheld circular saw. Use a sheet of paper wrapped around the tube as a guide and carefully cut the first ring off the tube. Cut it open by using a box cutter to slice through the ring’s width. Place the cut ring on the tube to use as a guide for all the remaining cuts.

Tape the ring together and place it a fraction more than two inches from the end if you are using a handsaw, or place it where the guide runs if you are using a handheld circular saw.

Here’s a better look at how to cut the concrete moulds.

Now, plan how to make the numbers. There are a few ways of doing this:
1. Lay out the stones first so you can simply transfer them to the concrete when ready, or
2. Get a bunch of house numbers to use as a guide. You will make an imprint of the house number and use that to set the stones in place.
You may be able to find these at the dollar store!

Set the rings on a plastic drop cloth and mix the standard concrete according to the instructions on the package. Fill each of the moulds ¾-full of concrete and use the trowel to smooth it out. Take care to remove any air bubbles. This base layer gives the stepping stones strength.

Follow the mixing instructions on the concrete package.

Mix the topping or repair concrete and add it to the top of each stepping stone. This layer gives the stepping stones a smooth, refined top.

Save the top 1/4 of the mould for the topping/repair concrete for a smooth finish.

Working quickly before the concrete hardens, it’s time to add the stones. If you have two people working together, one can be pouring concrete and smoothing while the other sets the stones in.

We used house numbers as a guide, but you can freehand it, use a foam number, or even just draw an outline with a stick. Once you have your method, start adding stones one by one, fitting them like a puzzle until you get your 1-9 completed.

Get creative! You can see how I also made a dragonfly stepping stone out of the pebbles.

Gently push a bit of concrete around the stones with your fingertips just to set them in place. If any do fall out, you can always glue them back in. I’m happy to report that not one of our stones fell out! That surprised me in a very good way.

Kiddo loves the hopscotch stepping stones!

Cover the stepping stones with a plastic drop cloth and let them dry for 24 hours. The next day, remove the mould by cutting it and set the stones in an airy place for a week to cure before moving them to the garden or lawn.

I set the hopscotch stepping stones through the garden surrounded by woolly thyme. I used 56 plants, so it should be a fuzzy, fragrant carpet surrounding the hopscotch in no time!

More Ideas for a Play Garden

A city girl who learned to garden and it changed everything. Author, artist, Master Gardener. Better living through plants.
Stephanie Rose

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August 25, 2025
Imagine fire-safe communities where residents can live and evacuate in record time

Twenty-five years from today, Santa Ana winds will scream through Los Angeles on a dry autumn morning, turning a small hillside campfire into a deadly, fast-moving blaze.

At that moment, the city will spring into action.

Los Angeles knows how to weather a crisis — or two or three. Angelenos are tapping into that resilience, striving to build a city for everyone.

Satellites will team up with anemometers, pairing live aerial footage with wind patterns to tell firefighters exactly where the fire is going. Fleets of autonomous Black Hawk helicopters and unmanned air tankers will fill the skies, dropping fire retardant in the path of the flames.

Wearable technologies will guide us in the city below: “ALERT: A wildfire has been spotted 2.4 miles from your location and will reach your location in approximately 43 minutes.” Angelenos will receive a live satellite map of the blaze’s trajectory and directions for a safe evacuation.

People in threatened neighborhoods will quickly run through to-do lists: close vents, check on neighbors, etc. Some renters and homeowners will arm fire-retardant sprayers on their roofs and jam valuables into fireproof ADUs tucked in their backyards. Others will have outfitted their super-smart homes with technology that cuts down on decision-making for an even quicker get-away. Apartment safety teams will follow their well-rehearsed plans to ensure evacuation.

Then, everyone will follow their community evacuation plan by driving their electric vehicles or ride-sharing to safety, eased along by a steady flow of green lights programmed by the city to divert all traffic away from the fire. Fleets of self-driving vans will circle back through the neighborhoods, picking up any stranded residents.

Michael Kovac’s house stands among burned homes in Pacific Palisades.

(Myung J. Chun / Los Angeles Times)

The scenario might seem improbable, but according to firefighters, architects and futurists, it’s a realistic outline of what L.A.’s fire defense could look like in 2050.

Devastating fires have pummeled Southern California in the last several decades, shifting the public conversation from fire suppression to fire preparedness and mitigation as governments begrudgingly acknowledge the disasters as regular occurrences. In the wake of the deadly January fires that burned through Altadena and Pacific Palisades, many people are wondering: Can we truly fortify our city against a firestorm?

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Architect Michael Kovac thinks we can. Kovac, a Palisades resident whose clients include celebrities, built his home to be fire-resistant knowing that, at some point, it would be subject to a firestorm.

Michael Kovac designed his home in Pacific Palisades The house is clad in fiber cement; the roof is made of fireproof TPO (thermoplastic polyolefin); the deck is made with specially treated wood for fire resistance; and a fire suppression system in the back of the house sprayed fire retardant onto the vegetation.

(Myung J. Chun / Los Angeles Times)

On Jan. 7, his entire street burned, but his house survived. Now, it serves as a blueprint for fire resistance. “We built it to be able to withstand a small fire,” Kovac said. “We never imagined our whole community would be erased.”

Kovac’s home is wrapped in fire-resistant fiber cement-panel siding. The green “living” roof is topped with grass and more than 4 inches of fire-resistant soil. The windows feature three panels of quarter-inch glass, which lessen the possibility of breakage in the face of scorching temperatures and protect the interior from radiant heat — one of the primary ways fires can enter a home.

Before fleeing the fire, Kovac loaded all his valuables into a room wrapped in concrete and equipped with a fire door capable of keeping out smoke and flames for three hours. He monitored the blaze from afar using security cameras. As the flames approached, he activated three sprinklers that sprayed fire retardant along the perimeter of the property, keeping the fire at bay.

Fire-proofing safeguards generally aren’t cheap. Fire-proof doors run from a few hundred dollars into the thousands, and fire-retardant sprinklers can cost tens of thousands of dollars, depending on the system. But Kovac also installed some DIY upgrades for next to nothing, including dollar-store mesh screens on all his vents to block embers from entering — another frequent cause of fires spreading.

Every improvement helps, but the harsh reality of the next 25 years is that across L.A., older structures that don’t comply with modern fire codes will burn. The collective hope is that by 2050, they’ll be replaced by fire-resistant homes, adding a herd-immunity defense to neighborhoods.

“The 1950s housing stock in the Palisades — smaller, older homes more vulnerable to fires — are all gone. I’m sad because I enjoyed the texture they brought, but whenever one burned, it made it likelier that the home next to it would also burn,” he said. “Now there’s a clean slate, so the neighborhood we build next will be more fire-resilient.”

The front garden at Michael Kovac’s home is filled with succulents and native plants and covered in volcanic rocks instead of mulch.

(Myung J. Chun / Los Angeles Times)

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Ken Calligar has the same hope.

“The housing replacement cycle is slow. It upgrades every 50 years or so, with 2% of homes being replaced per year,” said Calligar, the chief executive of resilient building company RSG 3-D. “But large-scale incidents like fires or earthquakes are an opportunity for a migration to a better system.”

Calligar’s company creates insulated concrete panels that are made with fire-retardant foam sandwiched between two wire-mesh faces, which are, in turn, wrapped in concrete.

The future of fire mitigation, he said, boils down to building with non-combustible materials.

“In California, 98% of homes have wood frames. All those homeowners have a future tragedy on their hands,” he added. “You can’t knock down all of California and start new, but you can mitigate portfolio damages by making new parts of the portfolio better.”

In addition, Calliger said, “By 2050, Californians should have a fire-proof place to store their assets in case of a fire. That way, you at least have something to get back to.”

Some home builders and designers are offering fire-resilient designs as demand continues to grow in the wake of the fires. KB Home recently unveiled a 64-home fire-resilient community in Escondido equipped with covered gutters, non-combustible siding and defensible space. The Santa Monica-based architectural firm SweisKloss offers fire-rated glazes and foam-retardant sprayers on its custom-built designs. By 2050, experts say, the vast majority of home builders will offer fire-resistant homes.

There’s a reason so many California homes are built with wood: It’s relatively cheap. There are plenty of futuristic building materials — including graphene, hempcrete and self-healing concrete, which is capable of repairing its own cracks after damage — but they’re not cost-efficient for most home buyers. Even traditional concrete, which stands up to the elements better than wood, runs roughly 20%-50% more than wood for home building, and building a fire-resistant home adds tens of thousands of dollars to the building cost, according to most experts.

For Daniel López-Pérez, the solution is a return to wood. Mass timber, specifically.

In addition to being a professor of architecture at the University of San Diego and a futurist, López-Pérez is the founder of Polyhaus, a home-building startup that says it can assemble a house in three days. To prove it, he put together a small prototype in his La Jolla backyard over a weekend in February. The 540-square-foot ADU is wrapped in 60 mass timber panels made of three 1.5-inch layers of plywood sealed together.

With traditional wood construction, the wood, studs and insulation leave plenty of room for oxygen, which fuels fires. With mass timber, the three layers are sealed with no air gaps, making them much more fire-resistant. When exposed to fire, the mass timber charcoals and burns a half-inch every hour — so a 4.5-inch panel would last six or seven hours before fully burning, he said.

The 540-square-foot Polyhaus ADU was assembled over a weekend in Daniel López-Pérez’s back yard.

(Daniel López-Pérez)

“It’s like in forest fires where big, old-growth trees survive by charcoaling. The exterior chars, but the inside survives.”

Mass timber is a new trend in fire-proofing; in this year alone, there are multiple conferences across the country dedicated to the engineered wood.

Lever Architecture, a firm with offices in Portland, Ore., and L.A., has helped pioneer the use of mass timber in the U.S. Among Lever’s projects are mass timber buildings for Adidas and the Oregon Conservation Center in Portland — and a mixed-use office/retail building at 843 N. Spring St. in Chinatown.

Mass timber projects are starting to sprout up across the Southland, including a multi-family development in Silver Lake and an office-retail complex in Marina del Rey.

Though his backyard prototype is his only model so far, Polyhaus has been flooded with inquiries after the January fires. He’s been telling customers that he can put a unit up in six weeks from start to finish, with 540-square-foot units running $300,000 all-in.

For López-Pérez, the future is also about using new technology, such as the robotic arms that assemble panels, to get more out of the stuff we’re already using.

“By 2050, we’ll be mixing ancestral materials with high-tech solutions,” he said. “Think Star Wars: a lightsaber in a cave.”

In the meantime, he suggests that instead of tearing down the 1950s tinderbox houses strewn across L.A.’s fire-prone hills, we should tack mass timber panels onto their exterior or interior to give firefighters hours, instead of minutes, to try to save homes once they catch on fire.::

Mass timber is one of multiple approaches that would make Brian Fennessy’s job easier. Fennessy, who serves as fire chief of the Orange County Fire Authority, has been fighting wildfires for 47 years. But over the last few decades, as blazes penetrate deeper into cities, he’s dealing with a different kind of problem: urban conflagrations.

Wildfires burn forests or brush, but urban conflagrations are fires that burn through cities. They’re becoming more common, and the toxic fumes released when homes burn present new dangers to his squad. “These are typically wind-driven fires, and they’re driving smoke into the lungs of firefighters,” he said. “We do blood draws, and early testing shows higher levels of heavy metal.”

Firefighters have a 14% higher chance of dying from cancer than the general population, according to a 2024 study, and the disease was responsible for 66% of career firefighter line-of-duty deaths from 2002 to 2019.

He hopes 2050 brings more safety precautions for his team, such as personal respirators for every firefighter and fleets of trucks that share their location in real time for better communication between departments, and he imagines fleets of drones flying alongside firefighting aircraft.

He’s also optimistic about funding and said he’s never seen so much legislative interest in putting money toward fire services as he has in the wake of the January fires. The Los Angeles Fire Department is one of the few city departments poised to gain new hires under Mayor Karen Bass’ $14-billion spending plan released in April, which proposed adding 227 fire department jobs while cutting 2,700 jobs in other departments.

A few weeks after the January fires, a California Assembly bill was introduced to explore the use of autonomous helicopters to fight fires. The choppers, including Black Hawk helicopters traditionally used for military operations, can be remotely programmed to take off, find fires and drop water where it’s needed. By 2050, experts hope firefighting stations will have entire fleets at their disposal to limit risk to pilots during shaky weather conditions.

In March, Muon Space launched a low-orbit satellite designed to detect wildfires early. By 2030, the company expects to have a fleet of 50 satellites circling the globe.

“The next few years are a pivotal moment for both fire services and citizens,” Fennessy said. “We have to get it right.”

Jack Flemming

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August 10, 2025
Md. company accused of underpaying workers’ overtime ordered to issue thousands in back pay – WTOP News

A Bowie, Maryland, based concrete subcontractor accused of denying dozens of workers their full pay is being ordered to pay thousands in back wages, the U.S. Department of Labor said Wednesday.

A Bowie, Maryland-based concrete subcontractor accused of denying dozens of workers their full pay is being ordered to pay thousands in back wages, the U.S. Department of Labor said Wednesday.

The company, V&V Construction Inc., classified “journey workers” as “skilled laborers” incorrectly and, as a result, underpaid them for overtime, the department said. Similarly, the subcontractor didn’t pay workers “their correct prevailing wages and fringe benefits,” the agency said in a news release.

Roberto Melendez, the department’s Wage and Hour Division district director in Richmond, said the investigation spanned from March 20, 2019 to March 17, 2021. Fifty-five workers “were not being paid the required wage,” he said.

“When it comes to the construction industries, we do have a problem there,” Melendez said. “This is an industry that we continuously find violations.”

WTOP reached out to V&V Construction for comment and has not yet received a response.

The DOL investigation found the company and its owners paid workers using a split rate of 25 hours per week as fully journey workers and 15 hours per week as skilled laborers. It also found the company submitted falsified payroll records and didn’t prove that it put up required worksite posters.

The workers, the investigation found, weren’t classified correctly on a federally funded housing project in D.C. They installed concrete as part of construction for Liberty Place Apartments in Northwest in August 2018. The company’s workers operated as a subcontractor to Hamel Builders of Washington LLC.

When the government pays for a project, Melendez said, “there’s usually a place in that contract where specified trades are paid a specified rate. And so that’s what this was all about. It was about skilled workers not getting paid the wage that was required.”

The DOL found that the company owed $195,492 in back pay to 55 workers, but the company didn’t make any payments and asked for a hearing with the Office of Administrative Law Judges.

The Office of Administrative Law Judges, meanwhile, upheld the findings and ordered V&V to pay $186,124 in backpay to the workers. Melendez said the agency tries to make sure the payments are made within 30 days.

The employers also agreed to a year and a half of independent monitoring of Davis-Bacon and Related Acts contracts “to ensure future compliance,” according to a news release.

Before its investigation, Melendez said the agency didn’t have a history of investigating the company for other violations. The agency, he said, can’t disclose the reason why it may launch an investigation.

In the construction industry, Melendez said violations are usually similar in nature, “where employees are not being paid either their proper rate, employees are either not getting paid for all the hours that they work, or they’re not being paid for the overtime that they also work.”

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Scott Gelman

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May 8, 2024
Make This Simple Rhubarb Leaf Concrete Bird Bath – Garden Therapy
Adding a bird bath is one of the best ways to increase the number of songbirds and wildlife in your garden. When set on the ground, birds use it for drinking, bathing, and cooling down. Here’s how to make your own DIY concrete bird bath using a rhubarb leaf!

The first time I tasted a tart rhubarb stalk dipped in sugar, I was hooked! The flavour is surprisingly complex for a stem, and when matched with something sweet, it’s a little slice of heaven.

The leaves, on the other hand, are not so tasty (which is good since they are toxic), but it’s such a pity that this prolific plant doesn’t have more culinary uses.

This DIY concrete bird bath is my attempt to get a little more out of my rhubarb plants. The ruffled and very large leaves make a wonderful mould for a bird bath. Once cast in concrete, these rhubarb leaves will live on forever and supply garden birds with a watering hole.

Here’s how you can make your own concrete leaf bird bath!

This is an easy weekend project.

Harvesting Rhubarb

To start this project, you’ll need some big, juicy leaves. We also want to make sure we’re not harming the rhubarb when we pick the leaves.

Let a new plant grow for two years before harvesting any stocks, and only take one-third of the plant in year three and beyond. After that, you can harvest the plant pretty heavily, leaving the smaller stalks behind after six to eight weeks of pulling off stems for pie and bird baths.

Follow the steps in this post to harvest rhubarb properly (you’ll twist, not snip).

For this rhubarb leaf bird bath, choose a firm leaf with a strong shape (if you can find any without holes, then congratulations, you have won the slug war!).

It’s best to start this project at the beginning of the season when the leaves are strongest and less chewed. A few nibbles or holes are expected in an organic garden and won’t take away from the final project.

Choose your leaf carefully, and try to use it fresh for your mould.

How to Make a Concrete Leaf Bird Bath

If you’ve never worked with concrete before, this is a great first project to try out. It’s simple but creates a beautiful result that you can display in your garden while helping the local birds.

Materials
- Large rhubarb leaf
- Rubber gloves, protective glasses, and a mask
- Repair concrete (see note)*
- Wheelbarrow or large bucket
- Water source (hose, watering can)
- Old trowel
- Plastic drop cloth
- Vegetable oil or cooking spray
- Stiff bristle brush
- Chisel and hammer (optional)
*Choose a lightweight concrete mix (less gravel) for a smoother finished product. Or, choose a heavier-weight concrete mix (more gravel) if the stones will be in high-traffic areas. The best concrete for small, decorative projects is repair concrete, which has no large pieces of gravel in it.

The bowl doesn’t need to be too deep to be effective for the birds.

Make It!

Wear protective gloves, glasses, and a mask, and mix the concrete according to the manufacturer’s instructions.

While the measurements and mixing instructions will be on the package, in general, you will want a large container to mix a whole bag at once. An old wheelbarrow is ideal as the height makes mixing a bit easier.

First, add the concrete to the container, then pour the recommended measure of water into the center. Stir thoroughly and use immediately. The consistency should be on the drier, firmer side. Add more dry mix if it is too runny.

You can also use a bucket for mixing.

Build a firm mound in the soil in the shape you want your bird bath to take.

Your mound will determine the shape of your bowl.

Lay the plastic drop cloth over the mound and place the leaf, vein-side up, on it.

Make sure the leaf’s vein is facing upwards to get the best imprint.

Spray the back of the leaf thoroughly with cooking spray or brush with oil.

Any vegetable oil will work for this.

Pile the concrete onto the leaf and pat it all around to compress the concrete and remove air bubbles. Spread the concrete to just 1/2″ from the edge of the leaf and gently round the extra 1/2″ of the leaf over the edge of the concrete. This will give the edges a more refined look.

Use your gloves to smooth out the edges for a more refined look.

Wrap the concrete in plastic and allow it to dry for 12 hours if the outside temperature is hot and dry or 24 hours if it is cooler and more humid.

Avoid doing this project if rain is in the forecast.

Gently peel off the leaf before the concrete is set, being mindful that it can easily break or crack at this stage. Generally, it’s preferable to wait until the concrete is completely dry to unmold it, but often, this leaves more plant material behind in the crevices.

Allow the concrete to cure completely according to the package instructions, then use a stiff bristle brush to scrub off any remaining plant material. You may also use a chisel and hammer to remove any concrete that has escaped the confines of the leaf, leaving the bird bath in a finished but still natural shape.

Set the concrete bird bath upright in the garden, on a raised wood stump or atop some overturned clay pots.

Leaving it closer to the ground will also allow other local wildlife to use the bird bath.

Caring for Your Concrete Bird Bath

Your concrete bird bath will handle the sun, the rain, and anything the warm weather can throw its way. But once the cold creeps in, you might want to retire your bird bath for the year.

Concrete is a porous material that is prone to cracking and chipping if not properly maintained. You can’t let water freeze in it, as this will cause small cracks.

Before the winter, drain it and bring it indoors where it is dry. Alternatively, you can drain it and cover it with something like a tarp until the springtime.

Frequently Asked Questions About Concrete Bird Baths

Is concrete safe for bird baths?

Concrete is safe for birds and one of the most effective ways to make a bird bath. The leaf imprint keeps them beautiful as well as functional for the birds.

Many bird baths you buy have been glazed for appearance and to make them easier to clean. But birds don’t like the glazing, finding it slippery and uncomfortable while trying to use the water.

Can you fix a broken concrete bird bath?

If your DIY concrete bird bath becomes cracked, you can resurface it. To do this, you will spread a layer of new concrete atop the old one, ensuring it’s moist and clean before applying the new layer of concrete. Apply the layer of concrete, then use a new leaf or two to get a new imprint.

Make a Bird-Friendly Backyard
Rhubarb Leaf Concrete Bird Bath

Attract more songbirds to your garden with this easy weekend project.

Safety gear (rubber gloves, face mask, apron, eye protection, etc.)

Wheelbarrow or large bucket

Water source

Old trowel

Plastic drop cloth

Stiff bristle brush

Chisel and hammer (optional)

Large rhubarb leaf

Repair concrete *see note

Vegetable oil or cooking spray

Put on protective gloves, glasses, and a mask. Mix the concrete according to the package instructions. The consistency should be on the drier, firmer side.

In your garden bed, build a dirt mound in the shape you want your bird bath to take.

Lay a plastic sheet overtop and place your rhubarb leaf on the plastic with the leaf vein facing up.

Spray the leaf with cooking spray or brush with oil.

Add a layer of concrete onto the leaf, gently patting it to remove air bubbles and to take its shape. Spread until you’re ½” away from the leaf’s edge, then gently round the edge of the leaf over the concrete to give the edges a refined look.

Wrap the concrete in plastic and allow it to dry for 12 hours if hot or 24 hours if it’s cooler outside.

Gently peel the leaf off the concrete before it’s fully dry.

Let the concrete cure fully according to the manufacturer’s instructions.

Use a stiff brush to scrub off any remaining plant materials.

Set your bird bath out in the garden!

For a smoother finish use lightweight concrete mix. For high-traffic areas, use heavier-weight concrete. Repair concrete is great for small, decorative projects.
Stephanie Rose

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April 15, 2024
The 1994 earthquake broke the 10 Freeway. How L.A. rebuilt it in record time
The Jan. 17, 1994, Northridge earthquake damaged roadways across Los Angeles. But nowhere was the impact felt more acutely that on the 10 Freeway just east of Culver City.

The earthquake knocked out two freeway bridges, at La Cienega and Washington boulevards. It cut off what was central Los Angeles’ key east-west traffic corridor.

Round-the-clock repairs got the Santa Monica Freeway opened in less than three months — in what officials described as record time, giving L.A.’s quake recovery an important boost.

The fire that damaged the 10 Freeway a few miles east this weekend — again closing the roadway indefinitely — has brought comparison to 1994.

“For those of you that remember the 1994 Northridge earthquake, Caltrans worked around the clock to complete the emergency repairs to the freeways, and this structural damage calls for the same level of urgency and effort,” Mayor Karen Bass said Sunday.

It remains unclear how badly damaged the freeway hit by Saturday’s fire is and how long it will take to fix.

Here is a review of that epic 1994 repair effort from the pages of The Times.

A race against time

Officials knew right away they needed to get the freeway operating as soon as possible.

Some economist said the freeway collapse was one of the most costly impact of the Northridge quake.

With an average of 341,000 vehicles a day using the roadway, they said, the extra time it took goods to get to their destinations and workers to get to their jobs cost millions in lost production and wages.

Reporting at the time suggested the closure cost the economy $1 million a day.

The freeway collapse pushed traffic onto crowded surface streets between Santa Monica and downtown Los Angeles, as frustrated commuters sought alternative routes. Detours caused delays of 20 minutes or more.

How was the freeway repaired?

An accelerated construction effort — one spurred by round-the-clock work — led to reopenings ahead of schedule. In the case of the 10 Freeway, which saw two sections flattened by the quake, contractor C.C. Myers Inc. finished the project 74 days ahead of schedule, allowing it to reopen in April— about three months after the quake knocked it down. The company had been offered a $200,000 bonus for every day the work was finished ahead of schedule, The Times reported.

The price tag on the project rose from the original bid of $14.9 million to nearly $30 million.

It was an intense process.
- The damaged structure was torn down, roadways were cleared and the rubble hauled away.
- Shafts up to 50 feet deep were drilled for piles, concrete was poured for columns and piles. This took about three weeks.
- Ironworkers created a frame of steel that was later covered with concrete. Because the structures were 600 to 700 feet long, construction of the bottom slab and vertical wall supports began on one end as the structures were erected at the other end.
- Once formed, the top deck was surfaced.
- After waiting five days for the concrete to cure, tension was applied to metal strands, called tendons, which were placed in the concrete to add strength to the structure.
- Although the freeway was deemed safe from collapse, experts said the bridge abutments needed even more strengthening with the installation of pilings to avoid damage in a future quake.
- Steel rings were placed around the columns during construction to further strengthen them. The rings were inserted around the rebar before concrete was poured.
- On each of the two bridges, four pilings 4 feet in diameter and as much as 80 feet deep were attached to the sides of each abutment.
Times staff

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November 13, 2023
How To Build A Climate-Friendly Skyscraper: Start Small. Petri-Dish Small.

Prometheus Materials has a solution for replacing one of the biggest contributors of greenhouse gasses, financial backing from Microsoft and an aggressive plan to scale up quickly.

_By_{Amy Feldman}_{, Forbes Staff}

We love concrete. We use it everywhere — skyscrapers, data centers, roofs, sidewalks, homes. The problem is, concrete doesn’t love us. Its key ingredient, cement, is the source of 8% of the world’s emissions of carbon dioxide, a gas that’s catastrophically warming the planet. But how do we replace a material that’s so inexpensive, so durable and so popular?

Prometheus Materials has an intriguing answer. The University of Colorado spinout is turning algae into cement using a process that’s similar to how coral and seashells naturally form. “Climate change is potentially an existential problem, and we’re finding that nature may have provided us with the keys to a solution,” says Loren Burnett, the company’s cofounder and CEO.

Prometheus is still in the early stages of commercialization with minimal revenue from a test facility in Longmont, Colorado, near Boulder. But it’s figured out the science and is now raising what Burnett expects will be between $15 million and $35 million in venture funding (plus additional project financing) to build a 35,000-square-foot factory to make at least a half-dozen different varieties of precast, bio-concrete products, including blocks, panels and pavers.

Burnett expects that the combination of the factory’s production and a licensing strategy that will allow it to sell its bio-based material in powdered form to producers worldwide will help it reach $75 million in revenue by 2027. “The key here is that we’ll leverage the large producers of cement and concrete using their production and distribution facilities,” he says.

That’s a big number, but even if Prometheus reaches that goal it’s barely a drop in the bucket for the more than $300 billion global cement industry. That helps explain why Prometheus is one of a number of startups now trying to tackle the hard problem of cement.

Biomason, for example, has developed a similar way to grow cement bricks and tiles with bacteria. Terra CO2, with a different low-carbon alternative to cement, has raised money from Bill Gates’ Breakthrough Energy Ventures. Brimstone Energy is working to commercialize carbon-negative cement and is building a pilot plant near Reno, Nevada with backing from venture firm DCVC. All three have gained more venture funding than Prometheus, with Brimstone raising $60 million, Biomason $87 million and Terra CO2 $99 million, according to venture-capital database PitchBook.

Gates, who wrote a book called How to Avoid a Climate Disaster, has called out the desperate need to come up with a cleaner and affordable alternative to cement to fight climate change. Cement is a major producer of greenhouse gasses both because of the chemical reaction that creates it and the fossil fuels required to heat the kilns where it’s produced. “We don’t have a way of doing it that’s clean, that doesn’t cost dramatically more, more than twice the price,” he told NPR’s Marketplace in 2021. “So if people think it’s just passenger cars and electricity, they’re going to miss what we need to do to get to zero.”

To bring the cement industry in line with the Paris Agreement on climate change, its annual emissions would need to drop by at least 16% by 2030, even as cement production is slated to increase, according to a 2018 report by the London-based think tank Chatham House. “This problem is so huge it’s going to take all of us being wildly successful,” Burnett says of his company and its competitors. “Everywhere you look, you’re going to see concrete. It’s ubiquitous.”

Petri Dish Days

Four University of Colorado Boulder academics, Jeff Cameron, Sherri Cook, Mija Hubler and Wil Sruber — all Prometheus cofounders and advisors — stumbled onto the idea while searching for a solution to a different problem.

They’d received a $2.4 million grant from the Department of Defense’s research arm in 2017 to see if they could use biology to produce protective structures in deserts and other remote environments with difficult terrain. “They knew they couldn’t fly in concrete because it’s too heavy, and they knew they didn’t want to truck it in over large expanses of hostile territory,” Burnett says. “So if they could use local materials to produce hardened structures to protect troops and high-value military assets, that’s what they wanted to do.”

The researchers began testing bacteria in petri dishes to see what they could come up with. At first they worked with ureolytic bacteria, which had been studied for civil engineering applications, but they eventually switched to cyanobacteria, commonly known as blue-green algae, which gets its energy from photosynthesis. As they delved deeper, the Defense Department asked them to make a little two-by-two cube of the material. “We learned quickly that a lot of the challenges we had to address were in the scale-up,” Hubler says.

Today, the company grows its algae in narrow 1,350-liter tanks with artificial seawater that’s full of nutrients, bubbled air to provide carbon dioxide and LED lights to mimic sunlight. Prometheus harvests the algae and puts it in a separate tank and, using a proprietary process, stimulates what’s called biomineralization — the formation of minerals into biological structures. “That’s our secret sauce,” Burnett says. The result is a slurry that it dries into a powder and combines with proprietary natural binders to create a zero-carbon bio-cement. The material can be mixed with the granular material known as aggregate to form bio-based concrete. The final bio-concrete blocks look pretty much like those made with the industry standard, Portland cement.

Decarbonization Bug

Burnett, 66, a serial entrepreneur, previously founded five companies, four of which were based on tech transfer from a university or a lab. In 2011, he created the now-dormant e-Chromic Technologies based on technology licensed from the Department of Energy’s renewable energy lab for a window technology that reflected infrared radiation back into the atmosphere to reduce the need for air conditioners and cooling. “That’s where I got bitten by the decarbonization bug,” he says.

In February 2021, the University of Colorado’s tech-transfer office connected Burnett with the four professors, and the next month they founded the company together.

GUERIN BLASK FOR FORBES

The early stages of a university spinout are tough because academic researchers can’t use their school labs for commercial work, but raising money takes more than just theoretical proof that the technology works. Cameron set up a basement lab in his house with fish tanks and bubbling apparatus purchased from pet stores. “We were sending samples to some of our investors that me and my kids actually made,” Cameron says.

A year later, the startup raised $8 million in venture funding led by European life sciences firm Sofinnova Partners that included strategic investors Microsoft, architectural firm Skidmore Owings & Merrill and roofing giant GAF. That enabled Prometheus to start pilot projects.

In a video, Microsoft president Brad Smith calls out the need for new innovations in concrete to bring down greenhouse gas emissions, singling out Prometheus and another company in which it’s invested, CarbonCure. “At Microsoft, we think about this a lot because a lot of concrete goes into our campuses and data centers,” he says in the video. Prometheus has since done a prototype project with Microsoft, which is building hundreds of data centers worldwide each year. “When we invest in emerging technologies, we look at if this is feasibly mainstream by 2030,” says Brandon Middaugh, senior director of the Microsoft Climate Innovation Fund, noting that the 2030 deadline of the Paris Agreement no longer seems so far away. “We see the potential is there, and there’s a pathway to scale for them.”

‘The Bleeding Edge’

Skidmore, Owings & Merrill, the global architectural firm known for skyscrapers that include the Burj Khalifa in Dubai, the tallest building in the world, and New York’s One World Trade Center, had also been looking for ways to reduce its carbon footprint with new materials. Four years ago, it began setting up partnerships with companies that could help, says Brant Coletta, managing partner and head of the firm’s global research and innovation team. In its partnership with Prometheus, it tested bio-materials to see if they could meet specs for things like strength and fire resistance. Working with masons, it built mockups and left them outdoors to see what might happen when exposed to the elements, then sprayed them with cleaners for additional testing. “We’re pushing them, and they’re pushing themselves, to get past all these tests so we can get to pouring concrete in skyscrapers,” Coletta says. “They’re at the bleeding edge of this.”

In February, Prometheus received industry certifications for both load-bearing and non-load-bearing blocks, an important step as it moves to commercialization. Skidmore, Owings & Merrill keeps pieces of the bio-concrete in its offices around the world for clients to see, and plans to exhibit a spiral-shaped sculpture at the Chicago Architecture Biennial this fall. While that may sound fancy, Coletta expects that the first major customer will be a data center.

There’s a lot that still has to happen to get Prometheus’ bio-cement into real projects, and the risks remain high. First it needs to raise the funds to build the factory, which it expects to get up and running in 2024, and then it needs to show it can successfully produce materials at a price customers will pay. It will also need to get its bio-cement past additional testing, and convince major concrete producers to take a chance. Burnett, who figures that the company will be producing at capacity and setting up licensing agreements by 2025, is determined.

“We have to decarbonize both cement and steel if we are going to be at net zero by 2050,” he says. “The math just doesn’t work without those two things happening.”

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Amy Feldman, Forbes Staff

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September 14, 2023