As the primary building material, concrete is essential for the construction of homes, skyscrapers, roads, bridges and airports, and can be found in virtually every aspect of our infrastructure. In fact, it is the second most consumed resource in the world, with only water being used at a higher rate.
But there’s a problem. The key ingredient in conventional concrete is cement, it’s what holds the concrete together. It’s also unfortunately a key contributor to a variety of environmental issues.
Cement is produced by burning limestone and other materials in a kiln at high temperatures. This process generates CO2 emissions, with almost one ton of CO2 being released for every ton of cement produced. As a result, the cement industry is the second-largest industrial contributor to CO2 emissions, accounting for nearly 8% of total global emissions and growing each year.
To address this issue, it’s crucial to consider alternatives to concrete that that can minimize environmental impact and help us build a more sustainable future.
Geopolymer: the sustainable alternative to cement
Researchers around the world are trying to find sustainable alternatives to cement that is less destructive to our planet. One very promising material to that is geopolymer concrete, which can completely replace ordinary portland cement (OPC) with concrete made from waste industrial products that last much longer and perform better.
The term geopolymer was coined by Joseph Davidovitz in 1978, when he came up with a pretty controversial theory on how the ancient pyramids were built. He didn’t believe that they were made of huge blocks of stone hauled up one at a time, instead he suggested that the blocks were formed by pouring crushed limestone, clay, lime and water into moles. This mixture then hardened into a fake synthetic stone that he called geopolymer.
Using the same theory, scientists have created a new type of concrete that is 100% free of cement using a variety of waste materials, industrial byproducts and minimally-processed natural substances. These materials are difficult to decompose and can affect the environment if left untreated, however when re-purposed into concrete they become safely encapsulated in building materials lowering the emissions of geopolymer concrete and forming a sustainable alternative to traditional concrete.
There are innovating companies all over the world using waste materials such as these, to create sustainable geopolymer concrete:
Fly ash
Fly ash (also called coal ash or pulverized fuel ash) is a byproduct of coal combustion from power plants that is mainly composed of silicon dioxide (silica - SiO2), aluminum oxide (AI2O3) and calcium oxide (CaO).
Metakaolin
Metakaolin is a highly reactive, finely ground, silica-rich material made from china clay or kaolin clay, which is typically produced through calcination (heating up) to 800 degree celsius.
Palm oil fuel ash
Palm oil fuel ash (POFA) is a byproduct of burning palm oil shells and husks as a fuel for electricity in palm oil mills. These are one of the largest agricultural wastes produced in Southeast Asia and has been found to be an effective cementitious material to replace OPC.
Ground granulated blast-furnace slag
Ground granulated blast-furnace slag (GGBS) is a byproduct of the iron and steelmaking industry, which is produced through the rapid quenching of molten slag with water.
The chemical reaction that produces geopolymer cement
Each of these raw powdery materials performs differently and produces a different type of geopolymer cement, but the overall chemical reaction can be summed up into this:
- The waste materials that contain silicon dioxide (SiO2) are mixed with alkaline activator such as sodium hydroxide (NaOH) or potassium hydroxide (KOH) + sodium silicate (Na2SiO3) or potassium silicate (K2SiO3).
- The silicon-oxygen-silicon bonds (Si-O-Si) then break down and aluminium atoms penetrate them to form aluminosilicate gels. With more alkali, these gels harden into geopolymer cement.
- The cement is then mixed with aggregate and water to form geopolymer concrete.
How we use fly ash to develop geopolymer concrete
While GGBS and POFA are nearly as popular in other parts of the world when it comes to sustainable building, here at EcoCrete we work with fly ash as the foundation to develop our geopolymer mix given the abundance of the waste material generated by the coal power plants across Indonesia.
Fly ash by itself is toxic, and if it ends up in landfill as waste products, it’s going to disperse into the air and can contaminate soil and water sources, posing significant risks to the environment and public health. But when recycled correctly, it can be turned into a supplementary cementitious material that replaces ordinary portland cement (OPC) to function as the sort of glue for the concrete when it’s mixed with water.
At EcoCrete, we’ve spent years of perfecting our properietary mix of geopolymer concrete made from fly ash and other repurposed materials, while eliminating the use of sand and other aggregates that are known to adversely impact the environment.
Here’s how we develop our geopolymer concrete in 3 steps:
Step 1: We start with our ingredients
We use a proprietary mix of waste materials from coal combustion that would otherwise end up in landfill as a replacement for the sand and aggregates that are traditionally used in concrete.
We’ve spent years of research and development coming up with the ideal mix, that isn’t just better for the environment it’s also stronger, lighter, more water and noise resistant and even less likely to crack than conventional concrete.
Step 2: It undergoes a chemical reaction
As these ingredients mix with water they undergo a chemical reaction that “geopolymerizes” the individual ingredients into a stronger, non-toxic and sustainable concrete.
Step 3: The result is geopolymer concrete
While our exact mix of ingredients is the result of years of investment in research and development, the end result is geopolymer concrete, just like the traditional Roman concrete that’s been around for centuries.
The benefits of our geopolymer concrete
Our innovative pozzolan mix has been proven to improve the concrete performance in both fresh and hardened state. Here are some of the major advantages of using our sustainable geopolymer concrete:
Carbon-negative footprint
The production of OPC is known to generate significant level of CO2, where for every ton of OPC cement made, approximately 0.9 ton of CO2 is released into the atmosphere. This is in contrast with geopolymer that only generates less than 0.2 ton of CO2 at the same volume of production. And because we take materials that would otherwise end up in landfill and encapsulate them in a long-lasting product, we essentially embed the carbon into the buildings resulting in a truly carbon-negative building material.
Stronger in tension and compression
Our structural concrete can reach a high compressive strength of 40 MPa (N/mm2) which enables you to grind the concrete slab without ever going too deeply and polish it in a way that gives you a more refined finished product.
Excellent waterproof properties
The concrete pores are smaller than 50 nanometers, so big molecules like water can’t just easily seep in and you can say goodbye to moldy walls and flaky paint.
Superior fire resistance
Unlike OPC concrete, EcoCrete’s products are highly resistant to fire - up to 1000°C - due to the fact that water in geopolymer concrete easily evaporates and does not explode the concrete from inside. As a result, it does not crack apart when heated (which is one of the main reasons why OPC concrete fails at high temperatures).
Fewer cracks
Geopolymer also reduces the heat of hydration that’s generated during the chemical reaction between cement and water, which can cause thermal stresses and lead to the formation of cracks. Reducing the heat will result in fewer hair cracks in the concrete when hardened.
10x life span
Just like its Roman-time predecessor, the geopolymer concrete offers increased value and durability as it can be applied to create structures that will last up to 10 times longer than ordinary Portland cement. That way, you can minimize maintenance costs, increase life expectancy and protect your investment in your building.
Let’s build sustainably
As population growth and urbanization continue to increase, the demand for sustainable concrete solutions will become even more pressing. By choosing to construct with sustainable concrete options, we can not only meet this growing demand, but also contribute to a more sustainable future. Geopolymer seems to be the growing common alternative to cement in concrete these days, and at the end of the day it can only positively affect our planet and help us reduce our carbon footprint which should be the end goal.
