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What is Carbon Capture in Concrete?
Carbon capture in concrete is a process that involves capturing carbon dioxide (CO2) from the atmosphere and incorporating it into concrete. This can be done by using a variety of methods, including:
- Adding mineralizers to concrete: Mineralizers are substances that react with CO2 to form minerals. These minerals can then be incorporated into the concrete, where they will remain for the lifetime of the structure.
- Using recycled CO2: Recycled CO2 is CO2 that has already been captured from the atmosphere. This CO2 can be used to make concrete in a variety of ways, including:
- By replacing some of the water in the concrete mix
- By replacing some of the cement in the concrete mix
- By using it to make a type of concrete called geopolymer concrete
Carbon capture in concrete has the potential to significantly reduce the environmental impact of the construction industry. Concrete is a major source of greenhouse gas emissions, and by capturing CO2 from the atmosphere and incorporating it into concrete, we can help to reduce these emissions.
In addition to reducing greenhouse gas emissions, carbon capture in concrete can also improve the properties of concrete. For example, concrete made with mineralizers is often stronger and more durable than traditional concrete. Concrete made with recycled CO2 is also often more sustainable, as it requires less energy to produce.
Carbon capture in concrete is a promising new technology that has the potential to significantly reduce the environmental impact of the construction industry. As the technology continues to develop, it is likely to become more widely used.
Carbon Capture Testing Plan
Evaluate effects of carbon addition to concrete mixtures:
|Property||Material||ASTM / Method||Details|
|Chloride Ion Penetration Resistance||Concrete||AASHTO T358|
Surface Indication of Concrete’s Ability to Resist Chloride Ion Penetration
Samples are cast or cored (4″x8″ or 6″x12″) and the resistivity across the specimens are measured by use of a 4-pin Wenner probe array. An alternating current potential difference is applied at the out pins by the apparatus, and the resultant potential difference across the two inner pins is measured. The current used and the resulting potential difference, along with sample area, are used to calculate the resistivity of the concrete. This has been found to relate to the resistance of the concrete to resist chloride ion penetration.
|Chloride Diffusion Coefficient||Concrete||ASTM C1556|
Apparent Chloride Diffusion Coeffecient of Cementitious Mixtures by Bulk Diffusion
A sample is cast or cored from a representative mixture to a depth of at least 3 inches (larger preferred). Samples are laboratory cured for 28 days, cut, sealed per ASTM C1202, then immersed in a calcium hydroxed water bath. A minimum of 35 days of immersion is performed, after which profiles are ground of varying depths. This material is then evaluated for chloride content per ASTM C1152, and a depth vs chloride content graph is used to calculate the chloride diffusion coefficient.
Rate of Absorption of Water by Hydraulic-Cement Concretes
Standard 4″ diameter x 2″ length specimens are obtained by molding or coring. Specimens are placed in a 50°C 80%RH environment for 3 days. Specimens are then placed in a sealed container for at least 15 days. Specimen sides are sealed, and placed in the absorption tank, and the rate of absorption is measured by recording the increase in specimen mass over time.
|Corrosion Potential||Concrete w/ Admixture||ASTM G109|
Effects of Chemical Admixtures on Corrosion of Embedded Steel Reinforcement in Concrete Exposed to Chloride Environments
Control specimens and specimens with admixture are cast with reinforcing bars placed per ASTM G109. A minimum of three replicates are tested in each condition. A salt solution is ponded on top of each specimen, and a high impedance voltmeter is used to measure the voltage across the resistor over time. At the same time, the corrosion potential is measured against a reference electrode placed in the salt solution per ASTM C876. Finally, at the conclusion of testing, chloride content is determined per ASTM C1152 for the control and the test specimens.
|Calcium Oxychloride||Cement Paste||AASHTO T365|
Calcium Oxychloride in Cement Pastes Exposed to Deicing Salts
Cement paste is ground to a powder and exposed to a 20% by mass calcium chloride salt solution. The powder is tested in a Low-Temperature Differential Scanning Calorimetry (DSC) machine, and the heat required to change the sample temperature is recorded as a function of the temperature throughout the test. Calcium oxychloride is determined by comparing the heat released, with the heat released from the phase change of pure calcium oxychloride.
|CO2 Based Masonry Properties||Masonry||AC520||Acceptance Criteria for CO2 Based Masonry Units|
Carbon Capture Testing Standards
Standards and acceptance criteria related to carbon capture testing:
- AASHTO T358 – Surface Resistivity Indication of Concrete’s Ability to Resist Chloride Ion Penetration
- AASHTO T365 – Quantifying Calcium Oxychloride Amounts in Cement Pastes Exposed to Deicing Salts
- ASTM C1556 – Determining the Apparent Chloride Diffusion Coefficient of Cementitious Mixtures by Bulk Diffusion
- ASTM C1585 – Measurement of Rate of Absorption of Water by Hydraulic-Cement Concretes
- ASTM G109 – Determining Effects of Chemical Admixtures on Corrosion of Embedded Steel Reinforcement in Concrete Exposed to Chloride Environments
- ICC-ES AC520 – CO2 Concrete-Based Concrete Masonry Units
More Information on Carbon Capture Testing
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