Reducing concrete production’s carbon footprint with precast solutions – towards net zero 

Sustainability in construction covers everything from materials to manufacturing, social responsibility, logistics, construction and the entire life cycle of the building, for example in terms of energy consumption and recycling. The construction industry and buildings in general create a lot of CO2 emissions. Concrete, for one, is seen as a high-impact material because it is used so much. Its usage will continue due to its unparalleled durability, structural strength, fire resistance, thermal mass, and usability in all climates. This is why a strong focus must be placed on lessening the environmental impact of concrete production. 

Did you know that a 14-story building emits 3750 tons of CO2 emissions over its 50-year lifetime? The biggest CO2 emission sources include building frame manufacturing, other structural elements, and later renovation. The building structures generate 46% of these lifecycle emissions, of which the building frame 32%. In this article we’ll focus on the building frame, because that’s where precast concrete, related technologies and innovations do their magic.  

One solution for the construction industry to meet sustainability criteria, to reduce emissions, is to opt for precast technology. Precast uses less of everything – less water, less cement, less steel, and less labor.    

For example, compared to cast-in-situ reinforced slab, hollow core slab production can use up to 45 percent less concrete and 30% less pre-stressing steel. Precast buildings are durable and airtight, and proper insulation can be integrated into hollow core slabs. Less work is required on the construction site, which also means less waste. Lighter buildings need lighter foundations.  

Not all precast is alike, and thus, opting for modern precast production lines is a way to further reduce CO2 emissions. Elematic is a leading precast concrete production technology provider.  

In the table above you can see that Edge is Elematic’s production line that uses better compaction, recycles fresh concrete, produces less scrap, and can be optimized using software. With modern equipment, cement consumption is also reduced by -50 kg/m3.  

Let’s take an example – Elematic’s Extruder E9 extrusion casting machine for producing hollow core slabs and Modifier E9 automatic machine for digging openings and recesses into the hollow core slabs significantly minimize concrete waste by enabling the recycling of concrete during production. This innovation is aligned with the precast concrete industry’s ongoing commitment to sustainability – and it provides monetary savings, too. 

While the CO2 emissions of the building frame can be reduced by choosing precast instead of cast-in-situ, using modern precast technologies, CO2 curing, recycled steel & plastic, green electricity, biofuel for heating, and transporting the elements with electric trucks, the concrete production itself is the main source of the emissions.  

Optimizing cement content is crucial for reducing the precast industry’s CO2 emissions, as cement accounts for up to 70 percent of a precast element’s carbon footprint. To reduce energy consumption, the precast industry could incorporate alternative cementitious materials, such as ground-granulated blast furnace (GGBS) slag from the steel industry and pulverized fuel ash (PFA) from coal-fired power stations. Both materials have significantly lower embodied CO2 compared to traditional cement. Additionally, materials such as microsilica, glass, limestone powder, and china clay waste can also replace Portland cement or primary aggregates, further enhancing sustainability. 

In other words, CO2 emissions can be significantly reduced with GWP 10 concrete, which refers to concrete that has a Global Warming Potential (GWP) of 10% from reference concrete, which means a 90% reduction in emissions. The GWP value is achieved by combining the GWP values for each ingredient of a concrete mixture, performing a reciprocal Life Cycle Assessment (LCA) of the entire concrete mix, and evaluating the total GWP for that concrete. 

Building frame emission reductions can reach ​-89% = 6.3 MEUR CO2 saving for 100 buildings, if all the enablers are taken into use.  

READ ABOUT SUSTAINABILITY IN PRECAST

Elematic is your partner to support in your sustainability journey. Please, contact us for any questions!