Group develops ecological cement

Pioneering line of research investigates properties and applicability of alternative product

Data from the Brazilian Institute of Geography and Statistics (IBGE) indicate that the Brazilian construction industry ranked third among the sectors of the national economy that grew the most in 2024, contributing to a 4,3% increase in the country's Gross Domestic Product (GDP). Although it has positive impacts on the country's development, this performance is also associated with higher greenhouse gas emissions: Portland cement, the main binder used in concrete production, requires the burning of limestone – the rock used in the manufacture of lime – at temperatures above 1.000 ºC, which implies the release of a huge amount of carbon dioxide into the environment.

“For every kilo of conventional cement produced, approximately 600 grams of carbon dioxide are emitted into the atmosphere, and Brazil currently produces around 60 million tons of cement per year,” says Carlos Eduardo Marmorato, a professor at the School of Civil Engineering, Architecture and Urbanism (Fecfau) at Unicamp. According to the professor, the market is unaware of the existence of alternative binders, making Portland the only option for building construction. “To give you an idea, this cement is second only to water in terms of per capita consumption worldwide.”

For about six years, Marmorato has been coordinating a line of research at Fecfau's postgraduate program focused on studying magnesium oxide, a chemical compound that has shown promising results in the production of alternative cements. Developed in 1867 by French civil engineer Stanislas Sorel, magnesian cement is as old as conventional cement. Its low density, good fire resistance and low thermal conductivity make it suitable for the production of lightweight panels, but the product has never had widespread application in industry due to a combination of lack of public awareness and limitations related to the material's durability when in contact with water.

The Unicamp group became a pioneer in the country in studying this technology. The first cycle of research, which included two master's degrees and three doctorates, involved recovering the product, expanding knowledge about it and improving it, resulting in the preparation of a book to be published later this year. As part of the research, the group also developed Brazil's first flat magnesium plate, a type of construction component that allows for greater versatility in finishes and coatings. Its use has proven to be especially suitable in the dry construction industry, involving systems such as drywall and light steel frame, which builds structures with galvanized steel.

According to Marmorato, this line of research aims to find solutions that help the Brazilian construction industry move away from masonry, a slow, artisanal system that limits large-scale construction. The new technology could accelerate, in particular, the production of homes for the lower-income population, which suffers from a housing deficit of around 6 million homes. “In the industrialized system, housing units are delivered faster and there are fewer construction losses. But we need to break with traditionalism, especially when we talk about government programs,” says the professor, noting that the private sector is much more advanced in this area.

Research

The first cycle of research concluded this year with the defense of her doctorate by civil engineer Elaine de Souza Freitas, who evaluated the influence of sugarcane bagasse ash on the mechanical properties of magnesian cement. Since it is a rich source of silica – a mineral that, when processed, improves the strength of concrete – it was thought that this ash could contribute to the durability and performance of magnesian plates, providing a more appropriate destination for waste from the sugar and ethanol industries.

Although the study found an improvement in product quality, it also found that sugarcane bagasse ash performs better as a filler for hardening cement, which makes it cheaper to produce flat panels. “The filler is an inert material that is important from the standpoint of volume and optimization, as it allows for a reduction in the amount of other components present in the formula,” says Marmorato, explaining that construction generally uses calcium carbonate as a filler, a substance also derived from limestone.

Previous research has studied the durability of magnesium cement, subjecting samples to pressure and contact with water to assess their resistance, as well as creating hybrid solutions containing magnesium oxide and Portland cement. In these tests, accelerated aging and degradation tests were performed, allowing researchers to check for decomposition or loss of mechanical resistance of the product. These observations demonstrated that the limitations regarding durability in contact with water can be perfectly overcome. As a result, the group was able to develop compounds that are as durable as traditional cement.

Currently, the research line is beginning a new cycle, open to researchers interested in continuing to improve magnesian cement. The intention is to continue the search for advances responsible for reducing greenhouse gas emissions and promoting dry industrialized construction systems, with a focus on closing plates for drywall e light steel frame. “These are the main axes of the research line. The greatest need in the construction industry is to optimize material consumption, together with the reduction of carbon gas emissions. So we need alternatives that are linked to lower emission volumes, but we also value faster, more personalized systems with less waste,” summarizes the professor.