CARBONATION CHAMBER

Why Concrete That Looks Fine Today Can Fail in 15 Years

Here's the uncomfortable part of working with concrete durability. A structure can pass every visual inspection for a decade and still be quietly losing its protective alkalinity underneath, until one day rebar corrosion shows up as cracking or spalling that nobody saw coming. Waiting decades to find out whether a concrete mix will hold up isn't an option for anyone doing real materials research, which is exactly why a carbonation chamber exists. It compresses a process that normally takes years into a controlled test that takes weeks.

Yatherm Scientific builds these as an accelerated carbonation chamber, meaning the CO2 concentration inside is deliberately raised well above atmospheric levels, so the same chemical reaction that happens slowly in the real world gets pushed through fast enough to actually measure. Engineers, materials labs, and civil research institutes use this data to make real calls on maintenance schedules and repair priorities instead of guessing.

What Carbonation Actually Does to Concrete

Carbonation is the reaction between CO2 in the surrounding air and hydrated cement minerals inside the concrete. Over time, this reaction lowers the material's internal alkalinity, and that drop is what removes the passive protective layer around embedded reinforcement steel. Once that layer is gone, rebar corrosion becomes a real risk, and corrosion is what actually compromises structural integrity, not the carbonation itself directly.

CO2 diffuses through the concrete's micro-pores and reacts with calcium hydroxide, forming calcium carbonate. That reaction disables the natural corrosion-resisting layer around the steel. It's a slow process outdoors, but a carbonation chamber for concrete testing recreates it under controlled temperature, humidity, and CO2 concentration so the depth of carbonation can be measured on a lab timeline instead of a building's lifespan.

The Actual Test Process

The standard procedure involves pre-curing samples every three months inside a temperature-controlled humid chamber. Samples then move into the carbonation test chamber where CO2 concentration is typically held between 1% and 5%, with temperature running from 20°C to 27°C. Relative humidity is usually set around 60% to 70%, close to a natural water body's ambient conditions, since maximum carbonation activity happens in that 40% to 80% RH band. After a three-month RH curing period followed by three months of active carbonation, visible cracking usually starts showing up on samples, which is the data engineers are actually after.

How Yatherm's Carbonation Chamber Is Built

The chamber uses a sandwich-type construction, with 304-grade stainless steel plates forming the interior and powder-coated mild steel making up the exterior. A standard 200-litre unit has an internal chamber of 600mm x 600mm x 600mm and handles up to 150 kg of concrete load at optimum performance, though larger volumes are available for bigger sample batches or multiple specimens tested in parallel.

Inside, humidity ranges from 40% to 80% RH and temperature runs from 20°C to 60°C, with CO2 concentration adjustable from 0 to 5% (higher concentration options up to 20% are also available for accelerated protocols). All of that is managed automatically through the control panel, and the front door seals the chamber airtight so the CO2 concentration you set is the concentration the sample actually sees, not something diluted by leakage.

Air Circulation, Humidity, and Heating

A quiet-running blower circulates air vertically and re-circulates it through the chamber, which is what actually keeps temperature and humidity uniform across every sample position rather than just near the sensor. Humidity is generated through steam injection, backed by a boiler tank with a float valve that manages water level automatically. Heating runs through durable SS tubular heaters with stainless steel fins for efficient heat transfer, paired with a CFC-free hermetically sealed compressor and a long-lasting condenser and evaporator coil for the cooling side.

CO2 Control: The Part That Actually Separates a Real Test Chamber From a Sealed Box

Yatherm offers a 0-20% CO2 range using pressurized CO2 cylinders and regulators, operated directly through the PLC with NDIR (non-dispersive infrared) sensors. These infra-red sensors maintain gas concentration inside the closed chamber with a high recovery rate after each door opening, and the PLC runs four preset programs at 5%, 10%, 15%, and 20% CO2 range, so switching between test protocols doesn't mean reprogramming from scratch every time. This is really what defines a proper carbon reaction chamber for concrete testing rather than a generic humidity cabinet with a gas line bolted on.

Standards, Applications, and Getting the Right Model

Yatherm's carbonation chambers are designed around IS 516 (Part 5/Sec 1):2018, EN 12390-12:2020, EN 13295, BS 1881-210:2013, and ISO 1920-12:2015, and they follow WHO and FDA 21 CFR Part 11 compliant control practices. That standards alignment matters if your lab's results need to hold up in an audit or get referenced in a structural assessment report.

These chambers get used by civil engineering research labs, cement and concrete manufacturers, government infrastructure testing bodies, and independent materials testing labs assessing repair or maintenance priorities on aging structures. If your protocol also calls for broader environmental cycling alongside carbonation testing, our environmental test chamber range covers combined temperature-humidity testing outside the CO2-specific workflow.

Yatherm Scientific manufactures these chambers in-house, which keeps pricing more reasonable than imported alternatives and means customization on chamber size, CO2 range, or load capacity is something we can actually do rather than just quote around. If you're comparing carbonation chamber price across vendors, it's worth checking whether NDIR sensors and PLC-based gas control are actually included standard, since that's usually where cheaper units cut corners.

Frequently Asked Questions

What is a carbonation chamber used for?

It's used to accelerate and measure the carbonation process in concrete, which helps predict rebar corrosion risk and structural durability over the material's real-world lifespan.

How long does an accelerated carbonation test take compared to natural carbonation?

Natural carbonation can take years to progress meaningfully. An accelerated carbonation chamber, by raising CO2 concentration well above atmospheric levels, compresses that timeline into a testing cycle of a few months.

What CO2 concentration range do these chambers support?

Standard units run 0% to 5%, with higher-range configurations available up to 20% CO2, controlled through PLC-based preset programs.

What temperature and humidity conditions are used during testing?

Typically 20°C to 27°C with 60% to 70% relative humidity for the CO2 exposure phase, since maximum carbonation activity occurs in the 40% to 80% RH range.

What size concrete samples can the chamber handle?

Standard 200-litre models handle up to 150 kg of concrete load with a 600mm cube internal chamber, and larger models up to 1000 litres are available for bigger batches.

What standards does the chamber comply with?

Construction and testing protocols align with IS 516, EN 12390-12, EN 13295, BS 1881-210, and ISO 1920-12, along with WHO and FDA 21 CFR Part 11 compliant controls.

How is CO2 concentration measured and controlled inside the chamber?

Through imported NDIR (infra-red) sensors that maintain concentration accuracy and recover quickly after door openings, managed automatically by the PLC controller.

Is the chamber airtight enough to hold a consistent CO2 level?

Yes, the front door seals the chamber airtight, which is essential for keeping the CO2 concentration accurate rather than drifting from ambient air leakage.

Can the chamber be customized for a specific concrete load or CO2 range?

Yes, chamber volume, CO2 range, and control configuration can be customized based on your sample size and test protocol requirements.

Working on a carbonation study and not sure which chamber size fits your sample count? Drop your load requirement in the comments, or reach out through our contact page and we'll help you spec the right model.