The United Nations estimates there are almost a billion poor people in the world, 750 million of whom live in urban areas without adequate shelter and basic services. An ingenious new building technology from scientists at Argonne National Laboratory and Casa Grande LLC could help alleviate and perhaps even solve that major humanitarian problem by providing affordable housing for the world’s poorest. A tough new ceramic material that is almost twice as strong as concrete may be the key to providing high-quality, low-cost housing throughout developing nations. The ceramic is called Grancrete, which, when sprayed onto a rudimentary Styrofoam frame, dries to form a lightweight but durable surface. The resulting house is a major upgrade to the fragile structures in which millions of the world’s poorest currently live. Using conventional techniques, it takes 20 men two weeks to build a house. A five person crew can construct two grancrete homes in one day. There’s also plenty of commercial upside in developed nations, making low-cost buildings viable for a variety of purposes – we can see inflatable technology marrying with Grancrete construction to evolve an entirely new way of building lavishly complex structures that would be impossible any other way. It’s hard to imagine it from the armchairs of most of those who will be reading this, but most of the world’s population live in low income shelter. The United Nations estimates World’s developing nations need more than 740 million homes NOW – if we built 100,000 homes a day for 20 years, we would be 20 years behind, so clearly we need to do something different if we are to ensure that all human beings can live with dignity. We need a low-cost building material and smarter construction process, so we can construct large numbers of houses to make the goal even remotely achievable. The Grancrete structural spray-on cement might be what we need.

 

Grancrete was developed by the Virginia firm Casa Grande in conjunction with Argonne. It is based on an Argonne-developed material called Ceramicrete, which was developed in 1996 to encase nuclear waste. The resilient Ceramicrete permanently prevents hazardous and radioactive contaminants from leaching into the environment.

"Originally, Casa Grande was looking for a concrete substitute for American industry, because concrete erodes in acidic conditions, says Casa Grande president Jim Paul. "But as I traveled in Venezuela, I recognized the demand for cheap housing, and I thought about how to use our material for that.

Casa Grande was still perfecting its concrete substitute, but its material, when dry, occasionally cracked. So Paul partnered with researcher Arun Wagh, a staff ceramist in Argonne’s Energy Techonology Division, to combine their technologies. Together they developed Grancrete.

According to experiments, Grancrete is stronger than concrete, is fire resistant and can withstand both tropical and sub-freezing temperatures, making it ideal for a broad range of geographic locations. It insulates so well that it keeps dwellings in arid regions cool and those in frigid regions warm. Currently, Grancrete is sprayed onto Styrofoam walls, to which it adheres and dries. The Styrofoam remains in place as an effective insulator, although Wagh suggests simpler walls, such as woven fiber mats, also would work well and further reduce the raw materials required.

Using Grancrete in developing countries also allows for two important criteria, says Wagh.

"When you build houses in these poor villages, the materials you use should be indigenous, and the labor should be indigenous, he says. "Every village has soil and ash, and the labor and training requirements are so minimal that two local people can build a house in two days.

According to Paul, workers only need two days of training to learn how to control and calibrate the machinery. Casa Grande typically assembles a team of five people who can start in the morning and create a home that residents can move into that evening. The material cures in 15 minutes, whereas concrete can take hours or days to dry.

Grancrete is made from an environmentally friendly mix of locally available chemicals.

"Grancrete is 50 percent sand or sandy soil, 25 percent ash and 25 percent binding material, Wagh says. Binding material is composed of magnesium oxide and potassium phosphate, the latter of which is a biodegradable element in fertilizer. So even if Grancrete were to decompose, he points out, it would revitalize the soil.

The cost of building a Grancrete home, estimated by Casa Grande at about $6,000 U.S. for labor and materials, is several times less expensive than a home built using conventional building materials. And the homes themselves are more than four simple walls. For less than $10,000 U.S., laborers can produce Grancrete dwellings of 800 square feet; a typical apartment in a city like Bombay, India, is only 400 square feet.

Wagh’s goal is to see Grancrete used throughout his native India and the world to produce housing for the poor. Born in the Indian state of Karnataka, Wagh grew up in a neighborhood where even to this day the homes have walls and ceilings made from knitted mats of palm leaves, and the floors are made of dried cow dung.

"These homes are regularly subjected to hundreds of inches of monsoon rains and cyclone winds and therefore often have to be repaired or even entirely rebuilt, says Wagh. "Obviously such conditions can have a great impact on the health, well-being, and longevity of the children and adults living there. The Grancrete spray-on cement now offers hundreds of millions of people such as these the opportunity to have adequate housing and live longer, healthier lives.

Argonne and Casa Grande have extensively field-tested Grancrete for structural properties, post-application behavior and production costs. Their next step will be to test it for both earthquake and hurricane resistance, after which they will make the product available worldwide. Wagh hopes the United Nations and other international organizations will step forth and subsidize mass-scale production around the world. And while Grancrete might sound too good to be true, Wagh’s response is "Believe it. It’s not magic. All we’re doing is making a better cement.

Grancrete Typical Properties

Compressive Strength

2 hours……………….. 3 000 psi
24 hours……………… 6,000 psi
7 days…………………. 6,500 psi
28 days……………….. 6,500-8000 psi

Combustibility

Does not burn. Retards the flame when coated on combustible materials such as Styrofoam.

Flexural Strength

1,300 psi after 28 days. Increased to 1,700 psi with fibers

Water Absorption

<1%

Freeze Thaw Resistance

Durability factor of 81 at 300 cycles

TheRmal Conductivity

0.53 w/m.k

Shrinkage

None. 1% expansion during setting.

Weight

Density of 2.1 grams/cubic centimeters density can be varied by aggregate addition.

Fracture Toughness

0.6 – 0.7 Megapascals.

Effect of Organic Gases

Insignificant.

Durability in water at given PH

No effect on material in pH range of 3-11.