Why have we made a CO2 calculator?
The construction industry is entering a transformation phase. During the last decades, the key decision parameters were time, money, and safety. However, in the years to come, a new parameter will start gaining importance – CO2.
With the rise of awareness of the need for more sustainable practices, the construction industry has seen its requirements and preferences change. It is no longer enough to just deliver on time and price. Owners, investors, and clients are starting to see the added advantages of sustainable buildings. Moreover, the regulations from governments and institutions are already changing to adapt to the new paradigm. In Denmark, for example, this governamental effort has materialised with the FBK (frivilligs bæredigtighedsklasse). The FBK is a new tool/regulation that aims to help the industry become more sustainable. This started on a volunteer basis but is planned to become compulsory in 2023. So, the big question is, how are the construction actors going to include this new parameter and find ways to benefit from it?
The problem
At Maturix, we have thought a lot about how we could help our clients to adapt to this change. We realized that the problem could be addressed from multiple angles. Part of the answer would be the use of EPDs (Product Environmental Declarations), using “green” concrete, or improving the recept mixes to optimize resources.
After many ideas, we decided to tackle one of the aspects that has the highest impact on CO2, which is cement content. More than 90% of the CO2 emissions that a concrete mix produces during its life cycle come from cement. Therefore, if the cement content is reduced so will the CO2 emissions. Some people might think that it is not possible to reduce the cement content due to safety and regulation concerns. This is partially true but misses a very important point. Many concrete elements end up achieving a strength almost 80-100% higher than its initial requirements stated. How is this possible?
This happens because there is a long process with a lot of partners involved. Let’s see an example to understand this process:
| Steps | Specified Strength |
|---|---|
| 1. The civil engineers specify the required strength based on the building’s constraints and safety margins. | 25 MPa |
| 2. The general contractor needs to fulfil the strength requirements within the time constraints. Therefore, he orders a concrete that fulfils 1. and reaches 20MPa in three days. Choosing this concrete will allow him/her to remove his formwork faster and be able to complete the job successfully. | 40 MPa (to reach 20MPa in three days) |
| 3. Due to liability and risk reasons, the ready mix factory may add one or two classes on top of what is required. This is done to be sure that the concrete will reach the desired 28 day strength without issues. | 50 MPa |
| 4. The result of all the previous decisions is an over engineered concrete. What started as a 25 MPa may end up being a 50 MPa due to the additional safety margins and the need to increase the process’ speed. |
The solution
We have designed a CO2 calculator to help the different actors understand the effect that early strength choices have on their CO2 emissions. We hope that this information can be used by general contractors, ready mixers, and sustainability consultants to make more informed decisions about their concrete choices.
Find the CO2 calculator here.
You can also read about the CO2 calculator methodology here.
