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Blog updates by Watershed Materials. Developments for sustainable new concrete block technology funded by the National Science Foundation.

New Geopolymer Masonry from Watershed Materials Turns Natural Clays Into Durable Building Products

Saw-cut half cylinder test sample of Watershed Materials’ new geopolymer masonry using natural clays. Test samples have achieved compressive strengths of 7,000 psi - twice the strength of ordinary concrete - with no cement, no fly ash, no blast furnace slag, and requiring no high temperature firing. The rich, red color comes from the specific clays used in the mix design. Different regional clays and aggregate will yield different color varieties with each location producing masonry visually linked to the palette of the surrounding landscape.

Watershed Materials has developed a solution to produce high strength masonry with a low carbon footprint using natural mineral based geopolymers. The technology allows for natural clays found readily all over the planet to be turned into reliable masonry products and offers a sustainable alternative to traditional concrete masonry. Recent test samples have achieved compressive strengths of 7,000psi - twice the strength of ordinary concrete - and have demonstrated remarkable resistance to water and chemical erosion.

Compressive strength testing of a Watershed Materials’ geopolymer test specimen. This sample, sandwiched between two steel caps equipped with neoprene pads to distribute loads, finally failed after being loaded with 100,000 pounds of force. This load equates to a compressive strength of 7,000 pounds per square inch, 350% stronger than the requirement for typical concrete masonry.

Concrete masonry is one of the world’s most common construction materials, used to build homes, schools, churches, apartment buildings and factories. Traditional concrete masonry, however, has a high carbon footprint due to its reliance on Portland cement, a material responsible for 6 percent of the world’s CO2 emissions.

“The implications for this technology are enormous,” says David Easton, Watershed Materials’ president and co-founder. “Using geopolymer technology to produce dependable building materials from natural clay minerals found throughout the developed and developing world is a local solution with global impact.”

Measuring linear drying shrinkage a test sample of Watershed Materials’ geopolymer masonry using a strain gauge precise to the thousandth of a millimeter. The extremely precise measurements made by the strain gauge will be corrected based on temperature then compared against measurements of a tempered steel reference instrument.
Clays, by nature, tend to shrink and swell upon drying and wetting, which can lead to problems when they are employed as construction materials. Mix design optimization and the modification of clay minerals through geopolymerization assists in overcoming many of the difficulties typically associated with clays and allows Watershed Materials to achieve minimal drying shrinkage in masonry products.

Watershed Materials’ technology, funded by the National Science Foundation, utilizes the geopolymerization of natural clay minerals and provides a more ecological, natural and globally available technology for producing building materials. Natural clays can be sourced from quarry and mine waste as well as construction site excavation. Masonry building products made with Watershed Materials’ technology inherit the visual appeal of their local production and appear more complex than typical grey concrete that is made from virgin mined rock washed of local color variations.

Geopolymers are a new technology that provide an alternative to Portland cement used in concrete and masonry. Until now, geopolymers have mostly relied on fly ash, a byproduct of burning coal, or blast furnace slag, a byproduct of iron and steel production. These industrial waste products are available only adjacent to coal fired power plants and steel production facilities, and the world does not produce enough to meet demand for concrete products. In place of these materials, Watershed Materials’ technology activates globally abundant natural clay-based minerals to form strong geopolymer reactions.

Applications for Watershed Materials geopolymer technology include:

A technician checking test specimens in an environmental chamber. Curing conditions are fundamental to the success of Watershed Materials’ geopolymer masonry production. In the factory or on-site production facility, masonry curing will take place on racks adjacent to the production facility. Another benefit of Watershed Materials geopolymer technology are relatively low curing temperature requirements; waste heat from hydraulic motors used by the production machinery can be reclaimed to marginally raise ambient temperatures for curing, supplemented by solar heating where necessary.

  • Mass production of sustainable masonry made from locally sourced, often recycled mine and quarry waste
  • On-site local production of structural masonry from excavation or demolition materials
  • Disaster relief and remote production of reliable building materials from locally sourced abundant materials

Clays have been used for thousands of years as a construction material, but traditionally require energy intensive, high-temperature kilning to overcome the tendency for clay to weather easily in rain and snow. Watershed Materials’ geopolymer technology changes the chemical structure of clays and allows their use in long lasting, high compressive strength, weather resistant masonry.

Measuring the liquid limit of clay minerals used in one of Watershed Materials’ geopolymer mix designs according to Atterberg Limits specifications. A careful understanding of the plasticity of each mineral component - the degree to which it will likely undergo changes in character as its water content changes - is paramount to determining its suitability for various stabilization approaches as well as target mix design proportions.

Watershed Materials first began to study mineral based geopolymers as an alternative to Portland cement in 2011. The company identified certain natural clay minerals as having properties that could be activated in a geopolymer reaction, but the process was difficult.

“These minerals were overlooked by others because they are not immediately reactive as a geopolymer” says Dr. Jose Muñoz, Watershed Materials’ director of technology. “We’ve solved the puzzle to allow natural clays to form geopolymer bonds for the production of high strength building materials.”

Dr. Muñoz and Taj Easton, Watershed Materials’ research lab manager, spent four years refining the process. Masonry produced with this technology will use less energy to produce, uses no cement, no fly ash, no blast furnace slag, requires no high temperature kilning, incorporates no dyes or colorants, and will open up previously overlooked, widely available natural and recycled materials as ideal for the production of durable building materials.

One of Watershed Materials’ first high-performance masonry blocks utilizing the geopolymerization of natural clay minerals. This geopolymer technology was developed during Watershed Materials’ Small Business Innovation Research grant supported by the National Science Foundation. The research team initially proposed to create a zero cement, 2,000 psi structural masonry block with this novel approach to geopolymer technology. With a year left to go in the research process, the team has surpassed that initial target by over 200% while demonstrating remarkable mechanical performances. The aesthetic gains over ordinary concrete block are a side benefit resulting from the character of local clays and aggregates. Variations in regional landscapes will produce masonry that is visually connected to local production.