Future Forward: Sustainable Infrastructure Requires Better Materials

It takes a lot of time, experience and education to understand the intricacies of the cement and concrete used to build infrastructure worldwide. With more than 40 years in the construction industry and the expertise to found a company seeking to create better materials, Hoff understands those intricacies better than most. Some aspects of my interview with him required secondary research to better comprehend the concepts, but one idea was clear: Hoff is no fan of Portland cement, the second-most abundant substance on the planet (after water).

“Portland [cement] is responsible for 8 percent of the [world’s] CO2 emissions,” he notes. “It only lasts 50 to 100 years, because carbonization starts to change the chemistry and it deteriorates. It’s not fireproof; it’s not waterproof; it doesn’t stand up to acid, which is basically our sewage; and then we have to come back and rebuild it, which is the exact opposite of sustainability.

“We’re building a society on some really crappy calcium binder,” he adds. “It’s not going to last. It deteriorates and falls apart.”

Look at Geopolymers

As founder of Geopolymer International, it’s not a surprise Hoff believes geopolymers are the best solution to replace Portland cement. According to Wikipedia, “a geopolymer is an inorganic, typically ceramic-like material that forms covalently bonded, non-crystalline (amorphous) networks.” Some people also use the term geopolymer to describe alkali-activated materials, but Hoff and most academics consider them separate products and not true geopolymers. 

The science behind geopolymers is complicated, but Hoff is used to trying to explain it simplistically.

“Geopolymer is basically a ceramic cement,” he notes. “You could say it’s an imitation granite rock using mostly silica and alumina. Basically, a polymer is a long chain of molecules, and we’re linking them together with a matrix of crystals of glass—silica.”

According to Hoff, geopolymers have myriad benefits. They have a higher strength than Portland cement; they’re also fireproof, waterproof, acid resistant, don’t require fresh water and last for thousands of years. In addition, they’re recyclable and can use local source materials as the main ingredient.

“The general rule of construction is anything over 500 miles away is too expensive to build with,” he notes. “So we work with people to look at their geology locally to see what’s available to be able to process and then make into a local geopolymer formula.”

Hoff admits geopolymers are more expensive than traditional cements, but researchers are working to refine techniques to lessen costs. In addition, long-term savings from durability and lower insurance rates can level the financial field.

“Our goals are to bring technology out and help people develop an alternative that’s sustainable,” he adds.

Advice for Engineers

Hoff believes the best way for engineers to start designing more-sustainable alternatives is through ongoing education, including review of all the new materials available.

“Start embracing some of the new technologies, because construction has been stuck in the mud for so long on the same techniques,” he adds. “We know the engineering, and we need to now institutionalize new materials and methods that will be able to get us there.”

In addition, Hoff hopes designers can move away from a “cost is everything” mentality and focus more on quality and sustainability.

“Construction is a very wasteful occupation,” he says. “We throw away a lot of waste, we overbuild, we use a lot of wood for cement formwork. There’s now a lot of technology that cuts away from resources like wood and plastics.”