Launch Slideshow

Stretching the Pour

Architects Stephen Kanner and Joe Addo are entering the building products industry with a concrete additive designed to help the people of Ghana.

Stretching the Pour

Architects Stephen Kanner and Joe Addo are entering the building products industry with a concrete additive designed to help the people of Ghana.

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    Bags of Pozzoghana-a local variety of pozzolana ash, a concrete additive-are now in production in a small factory in Ghana. The additive can stretch a bag of portland cement (a necessary ingredient in concrete) up to 30 percent, making the ubiquitous building product more affordable to the local market.

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    Kanner Architects

    The first project to use the Pozzoghana additive will be the Independence Avenue condominiums in the Ghanaian capital of Accra.

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    Kanner Architects

    Located on a street lined with embassies and near the main airport, the upscale complex will be a good testing ground for use of Pozzoghana on a commercial scale. Permits are in place; the project should break ground in the coming months.

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    Kanner Architects

    The second project to use the additive will be the Agostine Neto mixed-use project in Accra. Kanner and Addo won a design competition organized by a local developer, and the project should break ground next year.

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    Kanner Architects

    The second project to use the additive will be the Agostine Neto mixed-use project in Accra. Kanner and Addo won a design competition organized by a local developer, and the project should break ground next year.

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    Kanner Architects

    Spintex Road development: prefab cladding system using Pozzoghana

Concrete is one of the most consumed substances in the world, second only to water. In the West African country of Ghana, it is used to build seemingly every part of every kind of structure, from foundations and walls in single-family homes to patient rooms in hospitals, and it is the center of a cottage industry of concrete block makers, layers, and artisans. But because of the rising costs of importing portland cement (which is a primary ingredient of standard concrete), an economic crisis is brewing in Ghana, where some people now can't afford to build even the most modest of homes.

Enter longtime friends and architects Stephen Kanner of Los Angeles–based Kanner Architects and Joe Addo of Constructs in the Ghanaian cities of Accra and Tamale. Addo, after nearly 20 years in the United States, recently moved back to his home country of Ghana. On one of Kanner's visits (he is the godfather of Addo's child), the two men spoke with a friend of Addo's who was working with the Ghanaian government to analyze a variety of state-run projects.

One of the projects was a 20-year-old effort to test a concrete additive, a variation on traditional pozzolana ash, that stretches the use of a bag of portland cement by up to 30 percent. To test the durability of the pozzolana formula, the Ghanaian government built roads and structures using the material and simply waited to make sure they would remain structurally stable.

The buildings are still standing and still strong. Now the government was looking for someone to take over the manufacturing and marketing of the pozzolana product. Kanner and Addo jumped at the chance. “In a country like Ghana, things just take a long time,” says Kanner. “That's the way it is. I was lucky to be there at the right time.” Addo and Kanner bought the rights to manufacture with a third partner, PMC Global. “I am a shareholder, but most importantly, a Ghanaian advocate,” says Addo. With a five-year noncompete agreement from the government in place, the three-person joint venture has embarked on the process of making this additive commercially available under the name Pozzoghana.

  • Stephen Kanner
Kanner Architects
    Stephen Kanner Kanner Architects
  • Joe Addo
Constructs
    Joe Addo Constructs

Pozzolana is an additive that has been used as far back as ancient Rome, taking a claylike soil and burning it with a local firing agent in order to form a cementitious powder. Much like water added to soup, pozzolana will stretch the amount of concrete that can be mixed from a single bag of portland cement, without drastically modifying drying time, texture, or overall appearance.

The Pozzoghana formula makes use of local resources: the clay soil of the region to start, with the addition of palm kernel caps as the flammable substance. The soil that is used in Pozzoghana is only topsoil; collecting it does not require any strip mining, and it is very quickly regenerated. Palm oil is one of Ghana's biggest exports, and the nuts that provide the oil are structured like acorns, with a small cap that connects the kernel to the tree. The caps have simply been discarded for centuries, but they have chemical properties that interact with the clay of the soil to make pozzolana stable. Kanner describes the use of the palm kernel caps as “using something that is just sitting in piles by the side of the road,” and the Pozzoghana process in general as “very gentle, environmentally.” The clay and kernels are burned together in a kiln, using a series of careful heating and mixing techniques, and the end result is Pozzoghana.