Daring to Redefine Construction: The Geopolymer Revolution

7 min readOct 5, 2023


by Patrick Müller

The dome of the Pantheon was constructed using cement-free concrete and it withstands the forces of nature since ancient times (source: “Architas, CC BY-SA 4.0, https://commons.wikimedia.org/w/index.php?curid=70188093")
The dome of the Pantheon was constructed using cement-free concrete and it withstands the forces of nature since ancient times (Source: https://commons.wikimedia.org/w/index.php?curid=70188093)

In our quest for an industry of sustainable and ‘eco-friendly’ construction materials, the construction industry has witnessed a paradigm shift, and we want to belong to the first who adopt it on a bigger scale out of the laboratory into the wild. Increasingly, companies are moving away from traditional and, not in the good sense, old-fashioned building materials like ordinary Portland cement (OPC) and exploring more environmentally friendly alternatives. One such game-changing alternative is geopolymers, as we are convinced.

In this blog post, we’ll dive into the world of geopolymers, exploring what they are and why they are becoming the material of choice for modern construction, including Polycare’s modular building system.

Polycare’s next generation wall system. Reusable and dismantlable geopolymer-based CMUs (concrete masonry units). 100 % cement-free.
Polycare’s 4th Generation Masonry System; SEMBLA. Reusable geopolymer-based concrete masonry units (CMU’s). 100 % cement-free.

The Basics: What Are Geopolymers?

Geopolymers are a class of materials mainly used as cement and in concrete that have gained significant attention since becoming public in 1976 but even more in recent years due to their properties and eco-friendliness. They are typically formed through a chemical reaction between powdered stone-forming minerals (“aluminosilicate materials”) and an alkaline activator solution (“activator” or “hardener”). This reaction usually produces a strong, durable, and more environmentally friendly binding material.

Geopolymer concrete test samples utilising secondary raw materials: Ground-up bricks, fly ash, and steel slag. The greenish hue signifies successful chemical reactions.

Concrete is a class of materials in which mainly sands, and gravel (the aggregates) are bound together with a binder to form a new, robust, and durable material. Since about 1850, the binder of choice was Portland cement, but concrete has existed since ancient times. Although, one thing is certain: They did not use Portland cement back then. If so, then we wouldn’t know about their buildings because OPCs usage period is said to be only 80 to 100 years. Many infrastructure buildings in Germany, including bridges, display signs of weathering and deterioration in both their concrete and steel components after only 30 years of use.

A geopolymer can be seen as a contemporary adaptation of the exceptionally durable concrete used by the ancient Romans. It is a modern alternative to traditional concrete, offering increased resilience and sustainability. The main characteristics are attributed to the structure of chemical bonds found in geopolymers (via NMR analysis). Instead of relying on Portland cement, geopolymer concrete utilises a modern, 100% Portland-cement-free geopolymer to bind the concrete’s aggregates effectively and robustly.

Extract from Polycare’s company presentation: Our geopolymer-based material shows some similarities to ancient Portland-cement-free concretes. The material is already approved in Germany.

Geopolymers are sometimes called alkali-activated materials or alkali-activated aluminosilicates (AAM or AAA). Not only the name of this class of mineral binders is still a matter of debate. The frontlines in the battle over the correct terminology for geopolymers and their precise classification can sometimes become entrenched. That’s why at Polycare, we’ve decided to hire not only one but three experts in the field of geopolymers — some from each ‘camp.’ This approach has been working seamlessly (see picture below).

Polycare’s Material Science Team: Patrick Müller, Andreas Göbel, Dr Gaone Koma, Philipp Scherer ( left to right)

Geopolymers are composed of typical minerals found in the Earth’s crust. They share the same atomic composition as more than 80% of the Earth’s crust, exhibit a polymeric structure, and even possess a density (around 1.8g/cm³) within the range of ‘conventional’ polymers, such as plastics (1 to 2 g/cm³). That is why we believe ‘GEO-polymer’ is their most fitting name.

Composition of Earth Crust and Geopolymer

The composition of Earth crust and geopolymer (clay-based geopolymer, no aggregates) is remarkably close to each other. Polycare’s CMU (concrete masonry unit) called SEMBLA® for instance is from a fly ash-slag geopolymer with 75 to 80 % aggregates.

Key Characteristics and Advantages of Geopolymers in Construction

When considering the merits of geopolymers as an alternative to Portland cement, several attributes come to the fore:

  • Usability: Geopolymers emerge as a substitute for conventional Portland cement, which stands as one of the most extensively employed construction materials globally.
  • Strength and Durability: Geopolymers display remarkable compressive strength and durability, making them eminently suitable for various construction applications and frequently attaining compressive strength of up to 50 MPa. Polycare’s offerings reach an impressive above 90 MPa, and the most advanced geopolymer formulations reach an astonishing 190 MPa. In contrast, standard Portland cement concrete typically achieves only 25 MPa.
  • Carbon Footprint: Geopolymers notably reduce carbon emissions during production compared to traditional Portland cement. This attribute stems from the fact that the manufacturing of OPC involves the calcination (or ‘burning’) of substantial quantities of lime, which inherently comprises CO2.
  • Fire Resistance: Geopolymers demonstrate a high degree of resistance to fire, rendering them ideal for applications demanding fireproofing solutions.
  • Chemical Resistance: Their capacity to withstand exposure to various chemicals, such as sulfates, positions geopolymers as a good choice for industrial environments, infrastructural installations, and structures like sewer systems, where resilience to chemical agents is paramount.
  • Reduced Environmental Impact: Geopolymers use industrial byproducts, including fly ash or slag, thereby reducing the consumption of precious natural resources. Incorporating geopolymers into construction practices augments structural performance and fosters a more sustainable and environmentally responsible approach to building and infrastructure development.

Imagine this …

To produce ordinary Portland cement, you must heat a kiln to temperatures as high as almost 1500°C, and achieving lower temperatures is simply not feasible. In the cement plant, they utilise unconventional fuels like old tires, leftover deep-frying oil, and plastic waste in the name of ‘resource efficiency,’ burning stuff to reach the needed temperature contributes significantly to CO2 emissions, right?

However, only 33% of these emissions stem from such sources. To reiterate, just one-third of the emissions associated with cement production can be attributed to the burning of materials like tires and plastic waste to reach 1500°C. Regardless of the details, a staggering 66% of emissions result from the extraction of lime to create a hydraulic, active binder, as they say. This lime originates from seashells that absorbed CO2 from the atmosphere millions of years ago and safely stored it in the earth. Cement manufacturers release it back into the atmosphere solely so they can offer a cheap building material. This, in fact, is the reason why the industry relies so heavily on ordinary Portland cement, no matter the circumstances.

The remarkable inner dome of the Pantheon in Rome, a timeless inspiration for architects was constructed using cement-free concrete. Built in the 2nd century AD, it showcases intricate details and is a technical masterpiece even by today’s standards. (Source: https://commons.wikimedia.org/w/index.php?curid=963549“)

Why do We Choose Geopolymers for Modular Houses and Wall Systems?

The transition from traditional building materials to geopolymers in the construction of modular building and masonry systems (such as SEMBLA®) is driven by several reasons:

1. Sustainability:

Sustainability is at the core of the shift towards geopolymers. With the construction industry responsible for a significant portion of global carbon emissions, finding environmentally friendly alternatives is crucial. Geopolymers offer a way to reduce the carbon footprint associated with construction, making them an ideal choice for eco-conscious builders.

2. Energy Efficiency:

Modular construction relies on efficiency and speed. Geopolymers can be formulated to cure quickly, reducing construction timelines. Additionally, their excellent properties contribute to energy-efficient buildings, providing savings in both construction and operational costs.

Geopolymer consist of the material from which our Earth crust is primarily ‘made’ of.

3. Strength and Versatility:

Geopolymers are renowned for their exceptional strength and versatility. This makes them suitable for a wide range of applications, including load-bearing walls, cladding, and even interior finishes, allowing for versatile and robust modular designs.

Our roadmap at Polycare extends beyond just a masonry system. The material properties suggest an excellent foundation for developing products for the entire building envelope, including roofing, flooring, and foundations. Watch the space … ;)

4. Fire Safety:

Modular constructions often require strict fire safety standards. Geopolymers’ inherent fire resistance provides added peace of mind, ensuring that modular structures meet safety regulations.

Geopolymers are the ‘synthetic’ equivalent of natural occurring stones. Both are impossible to burn. Plus, OPC can literally explode because it is a water-containing crystal.

Geopolymer concrete belongs to the class of incombustible building materials.

5. Reduced (Maintenance) Costs:

Geopolymers have low maintenance requirements, contributing to long-term cost savings for modular housing and reusable wall systems. Their resistance to chemicals and environmental factors ensures durability over time.

We expect our geopolymer materials to have a much-extended period of usability. OPCs is only 50 years.

The Future of Geopolymers in Construction

As the construction industry continues to evolve towards more sustainable practices, geopolymers are poised to play a pivotal role. They offer a solution to reduce environmental impact while providing just the right performance characteristics. For companies like Polycare, embracing geopolymers for modular building and masonry systems represents a significant step towards a more sustainable future.

Geopolymers are not just an alternative to traditional building materials; they represent a sustainable revolution in construction.

Their strength, durability, and eco-friendliness make them an ideal choice for modular housing and wall systems. By adopting geopolymers, our places of work and learning, homes, and ultimately our life, are not only contributing to a greener planet but also setting the standard for innovative and sustainable construction practices. The future of construction is here, and it is geopolymer-driven.

Author: Patrick Müller, Material Scientist at Polycare — Materials Engineer, Author and Geopolymer Specialist




To drive empowerment and circular economy, Polycare develops innovative construction technologies, that make sustainable habitats affordable.