Humidity Chamber for Cement Testing

A moist (humidity) chamber (also called curing cabinet/curing room or climatic chamber) is used to store demolded cement/mortar/concrete specimens in controlled temperature and high relative humidity so test results (strength, shrinkage, setting, etc.) are repeatable and compliant with test standards. It keeps air saturated (fog/mist or warm water evaporation) and usually records temperature and RH continuously.

Typical standard requirements (practical baseline)

• Temperature: typically 23 ± 2 °C (some labs use 20–27 °C for specific tests; check the test standard you follow).
• Relative humidity: ≥ 95% RH (air should be essentially saturated).
• Control & recording: temperature recorder and a reference thermometer placed near specimens; RH and temp instruments must be calibrated.
• Construction: durable, non-corroding interior; tight-fitting doors; shelving that allows air circulation; fog/spray/misting or water curtains to maintain saturation.

Key standards you’ll look at: ASTM C511 (mixing rooms, moist cabinets, moist rooms for cement/concrete) and national standards such as IS 4031 parts for cement testing (look up the specific part for the test you’re running).

Types of chambers (choose by need)

1. Benchtop moist cabinet — small, for mortar cubes/paste (compact, lower cost). Good for university/batch lab.
2. Walk-in curing room — for larger batches or many specimens; requires HVAC/misting / VaporPlus systems to keep RH high.
3. Environmental / climatic chamber — allows set T and RH across ranges (useful if you must run non-standard curing regimes).
4. Pressurized HPHT curing chambers — for oilwell cement testing (high temperature & pressure). Not typical for ordinary cement labs.

Recommended minimum specification checklist (for purchasing or building)

• Interior: stainless steel or painted anti-corrosive lining, smooth surfaces for cleaning.
• Capacity: specify racks/shelves to hold your typical number of cubes/cylinders (e.g., 100×50 mm cubes).
• Temperature control: ±1–2 °C stability; heated/cooled as required.
• Humidity control: active fogging/misting with water-spray distribution or water curtain; maintain ≥95% RH.
• Sensors & logging: calibrated temperature and RH probes near specimens + data logger (continuous recording).
• Door: tight gasket, observation window optional.
• Safety: overflow/drain, low-water alarm, over-temp cutout.
• Power & plumbing: access to water supply for misting and drain for condensate; consider water softening if your water is hard.
• Standards compliance: vendor statements that chamber meets ASTM C511 (or equivalent) — ask for conformity documentation.

Typical operating procedure (practical)

1. Prepare specimens and demold per the test standard (timing depends on the test).
2. Place specimens on racks ensuring free air circulation around each specimen.
3. Set chamber to 23 ± 2 °C and run fogging until RH ≥95% (confirm with RH probe).
4. Keep continuous logged records of T & RH for each curing period.
5. Calibrate/verify sensors weekly/monthly (and before major tests) against a reference.

Validation & calibration (must-do)

• Calibration: temperature probes and RH sensors must be traceably calibrated (certificate) — do this at least annually or per lab QA.
• Validation run: before using, run an empty chamber for 24–48 h and confirm uniformity (record temp/RH at multiple rack locations).
• Records: keep logs for traceability (standards auditors will ask).