{"id":38342,"date":"2024-03-26T16:48:18","date_gmt":"2024-03-26T16:48:18","guid":{"rendered":"https:\/\/www.alicat.com\/?post_type=article&p=38342"},"modified":"2026-01-26T16:19:23","modified_gmt":"2026-01-26T16:19:23","slug":"co2-beton","status":"publish","type":"support","link":"https:\/\/www.alicat.com\/de\/support\/co2-concrete\/","title":{"rendered":"Sequestrierung von CO2 in Beton\u00a0"},"content":{"rendered":"\n[et_pb_section fb_built=”1″ _builder_version=”4.23.1″ _module_preset=”default” global_colors_info=”{}” theme_builder_area=”post_content”][et_pb_row _builder_version=”4.23.1″ _module_preset=”default” global_colors_info=”{}” theme_builder_area=”post_content”][et_pb_column type=”4_4″ _builder_version=”4.23.1″ _module_preset=”default” global_colors_info=”{}” theme_builder_area=”post_content”][et_pb_heading title=”Sequestering CO2 in concrete ” _builder_version=”4.23.1″ _module_preset=”default” global_colors_info=”{}” theme_builder_area=”post_content”][\/et_pb_heading][et_pb_text _builder_version=”4.27.4″ _module_preset=”default” global_colors_info=”{}” theme_builder_area=”post_content”]The production of cement, the binding element in concrete, accounts for 7% of total global carbon dioxide (CO2<\/sub><\/a><\/span>) emissions. Concrete is one of the most-used resources on Earth, totaling an estimated 26 billion tons produced annually worldwide. Due to global demand growth, production isn\u2019t expected to slow down for at least two more decades.\u00a0<\/span>\u00a0<\/span>\n\nConcrete is made up of aggregate materials, primarily rocks and sand, along with cement and water. As about 80% of concrete\u2019s carbon footprint comes from the cement component, researchers have been working to find more suitable materials to reduce such carbon emissions. Apart from developing blended cements and\u00a0<\/span>algae-based cements<\/span><\/a>\u00a0to reduce CO<\/span>2<\/sub><\/span>\u00a0emissions, researchers and private companies are also focusing on tapping into new ways to use captured CO<\/span>2<\/sub><\/span>\u00a0as an ingredient in the cement itself, locking it away and preventing it from entering the atmosphere.\u00a0<\/span>\n

What are carbon-conditioning and CO2<\/sub>\u00a0curing?<\/span><\/h2>\nCurrently, in order to accomplish this, CO<\/span>2<\/sub><\/span>\u00a0is either added to aggregates by injection during mixing in a process called carbon-conditioning or after concrete has been cast in a process called carbonation curing or CO<\/span>2<\/sub><\/span>\u00a0curing. These processes transform gaseous CO<\/span>2\u00a0<\/sub>to carbonate minerals that can be stored indefinitely without causing global warming. Precast concrete is capable of storing more CO<\/span>2<\/sub><\/span>\u00a0than cast-in-place concrete. Whereas cast-in-place can store up to 3.8% of its total mass in CO<\/span>2<\/sub><\/span>, precast can store\u00a0<\/span>as much as 9.6%<\/span><\/a>\u00a0of its total mass in CO<\/span>2<\/sub><\/span>.\u00a0<\/span>\u00a0<\/span>\n\nAside from reduced CO<\/span>2<\/sub><\/span>\u00a0emissions, this process also\u00a0<\/span>improves the strength<\/span><\/a>\u00a0of concrete approximately 10 to 20 percent depending on the mix. Therefore, concrete made using CO<\/span>2<\/sub><\/span>\u00a0curing actually requires less cement, further reducing amounts of related CO<\/span>2<\/sub><\/span>\u00a0emissions. Moreover, as less materials are required, CO<\/span>2<\/sub><\/span>\u00a0curing leads to lower production costs and larger revenue margins for concrete manufacturers.<\/span>\u00a0<\/span>\n\nIn the following, we will explain both the carbon-conditioning and carbon-curing processes and how Alicat\u2019s\u00a0MC-Series<\/a>\u00a0of mass flow controllers provide all-in-one metering solutions for these applications.\u00a0<\/span>\u00a0<\/span>\n

Carbon-conditioning<\/strong><\/span>\u00a0using MC-Series mass flow controllers<\/span><\/h2>\nIn carbon-conditioning<\/span><\/a>,\u00a0CO<\/span>2<\/sub><\/span>\u00a0is injected directly into aggregates during the mixing stage.<\/span>\n\nFor this process, different CO<\/span>2<\/sub><\/span>\u00a0sources with different advantages and disadvantages can be used, including pure CO<\/span>2<\/sub><\/span>\u00a0gas, flue gas, or blended gas mixes. Whereas pure CO<\/span>2<\/sub><\/span>\u00a0tanks are more costly and must either be purchased externally or created internally using CO<\/span>2<\/sub><\/span>\u00a0separation procedures, flue and blended gases are more affordable options that reclaim direct emissions from industrial processes. Conversely, pure CO<\/span>2<\/sub><\/span>\u00a0gases offer faster reaction times and are easier to store.<\/span>\u00a0<\/span>\n\nRegardless of which CO<\/span>2<\/sub><\/span>\u00a0source is used, aggregate materials are placed into a temperature and humidity controlled curing chamber and then pressurized by the gas source using a pressure controller, such as an Alicat MC-Series mass flow controller running in\u00a0pressure control mode<\/a>. Depending on which gas source is used, this generally varies somewhere in the range of 150 kPaG-500 kPaG (although sometimes ambient conditions are used). Greater pressures will allow for quicker reactions. MC-Series mass flow controllers regulate the process pressure while taking mass flow and temperature data.\u00a0<\/span>\u00a0<\/span>\n

Open-inlet systems<\/h3>\nIn open-inlet systems, or constantly flowing systems, chamber pressure and temperature are roughly unchanged during the reaction due to fresh CO2<\/sub> consistently replacing sequestered CO2<\/sub>. The reaction therefore concludes when the flow rate of gas drops near to zero, signaling that no more CO2<\/sub> can be stored in the concrete. Additionally, temperature drops also determine that the process has ended. Once these predetermined flow rate or temperature endpoints are reached, the mass flow controller running in pressure control mode signals via a PLC or computer to close off the gas supply.\n\nAlicat\u2019s\u00a0<\/span>MC-Series<\/span><\/a>\u00a0of mass flow controllers running in pressure control mode can provide continuous, fast-response, pressure control through a PID-control loop to automate the process while simultaneously recording critical temperature and mass flow data which also monitor and control the process via a PLC or computer.<\/span>\u00a0<\/span>\n\n [\/et_pb_text][et_pb_image src=”https:\/\/www.alicat.com\/wp-content\/uploads\/2024\/04\/Concrete-setup.webp” title_text=”Concrete-setup” align=”center” _builder_version=”4.23.1″ _module_preset=”default” module_alignment=”center” custom_padding=”20px|20px|20px|20px|false|false” global_colors_info=”{}” theme_builder_area=”post_content”][\/et_pb_image][et_pb_text _builder_version=”4.23.1″ _module_preset=”default” global_colors_info=”{}” theme_builder_area=”post_content”]

Closed-inlet systems<\/h3>\n

In closed-inlet systems, CO2 <\/sub>is added until reaching a chamber pressure setpoint, after which, the gas supply is turned off. Since the system is now closed after pressurization and airtight, the temperature, the CO2<\/sub> concentration, and the gas pressure in the chamber will be reduced as the concrete absorbs CO2<\/sub>. CO2<\/sub> sensors attached to the chamber signal when all CO2<\/sub> has been used and all remaining gas is vented via an electric valve. New CO2<\/sub> gas is then added and the process is repeated cyclically until CO2<\/sub> is still detectable by the CO2<\/sub> sensors and no significant temperature or pressure change is observed anymore.<\/p>\n

In addition to controlling the cyclical gas flow, just as in open-inlet systems, Alicat\u2019s MC-Series of mass flow controllers running in pressure control mode with CO<\/span>2<\/sub><\/span>\u00a0sensors in closed-inlet systems signal to the control loop when the process is over based on either temperature or pressure data. When the pressure and temperature no longer decrease over time and CO<\/span>2\u00a0<\/sub>levels do not drop towards zero, the control loop ends the process. Alternatively, when the temperature and pressure decrease over time but CO<\/span>2\u00a0<\/sub>levels drop towards zero, the control loop vents remaining chamber gas via an electric valve and adds more CO<\/span>2<\/sub><\/span>.<\/span><\/p>\n

Carbon-conditioning using PC3-Series pressure controllers<\/h2>\n

Alternatively, an Alicat\u00a0PC3-Series<\/a>\u00a0pressure controller can automate the process based on just pressure setpoints. In the open-inlet process, the PC3-Series pressure controller sets the chamber pressure and ends the process when it begins to rise above the setpoint. In the closed-inlet configuration, the PC3-Series pressurizes the chamber and then batch adds more CO<\/span>2<\/sub><\/span>\u00a0as the chamber pressure decreases and CO<\/span>2<\/sub><\/span>\u00a0levels decrease over time. When the chamber pressure and CO<\/span>2<\/sub><\/span>\u00a0levels remain constant, the PC3 signals to the control loop to vent all remaining gases via an electric valve and to end the process.\u00a0\u00a0<\/span>\u00a0<\/span><\/p>\n

To track the amount of CO<\/span>2<\/sub><\/span>\u00a0or mixed gases being used in either open-inlet or closed-inlet systems, Alicat\u2019s MC-Series includes totalizer and batching options, allowing for easy, automated calculations of how much CO<\/span>2<\/sub><\/span>\u00a0is being sequestered, creating a traceable record which may be useful for reasons such as tax incentives. \u00a0<\/span><\/p>\n

CO<\/strong><\/span>2\u00a0<\/sub><\/span>curing using MC-Series of PC3-Series controllers<\/strong><\/span><\/h2>\n

Carbonation curing<\/span><\/a>, or CO<\/span>2<\/sub><\/span>\u00a0curing, describes CO<\/span>2<\/sub><\/span>\u00a0sequestering in entire concrete blocks after the mixing stage. The process is similar to carbon-conditioning aside from this difference. Just as in the carbon-conditioning system configurations, a humidity, temperature, and pressure controlled chamber is utilized in combination with CO<\/span>2<\/sub><\/span>\u00a0gas sources, pressure transducers or controllers, and CO<\/span>2<\/sub><\/span>\u00a0sensors.<\/span>\u00a0<\/span><\/p>\n

Just as in carbon-conditioning, Alicat\u2019s\u00a0<\/span>MC-Series<\/span><\/a>\u00a0of mass flow controllers can help to reap the full benefits of CO<\/span>2<\/sub><\/span>\u00a0curing.<\/span><\/p>\n