The concept behind the Grancrete® system is simply to combine state-of-the-art materials with modern techniques to create structures that can be built anywhere in the world using local labor forces and mostly locally produced materials. Extremely durable structures can be built quickly and economically under virtually any topographic climatic conditions.
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
2 hours……………….. 3 000 psi
24 hours……………… 6,000 psi
7 days…………………. 6,500 psi
28 days……………….. 6,500-8000 psi
Does not burn. Retards the flame when coated on combustible materials such as Styrofoam.
1,300 psi after 28 days. Increased to 1,700 psi with fibers
Freeze Thaw Resistance
Durability factor of 81 at 300 cycles
None. 1% expansion during setting.
Density of 2.1 grams/cubic centimeters density can be varied by aggregate addition.
0.6 – 0.7 Megapascals.
Effect of Organic Gases
Durability in water at given PH
No effect on material in pH range of 3-11.