| Property | Typical Value | | :--- | :--- | | Dry Density | 125 – 155 lb/ft³ (2000 – 2480 kg/m³) | | Absorption | 4 – 8% | | Permeable Voids | 12 – 18% |
Because time is not the same as energy. A sample soaked at room temperature for a month will still have trapped air in pores smaller than 0.1 microns. Boiling forces water into those nano-pores. ASTM C642 is deliberately aggressive. It measures permeable voids—the voids that actually connect to the surface and can transport water. astm c642 density absorption voids in hardened concrete
Note: Values >20% permeable voids generally indicate poor-quality concrete or a mix design error. | Property | Typical Value | | :---
So, the technician brings out the hot plate. The sample is boiled in distilled water for . Boiling reduces the surface tension of the water and expands the air in the pores, driving it out. After boiling, the sample cools overnight while still submerged. ASTM C642 is deliberately aggressive
By J. Carter, Materials Field Engineer
[ Absorption = [(B-A)/A] \times 100 ] What it means: The concrete’s appetite for water. High absorption (typically >8% for normal concrete) suggests a permeable matrix vulnerable to freeze-thaw damage and chemical attack.
Armed with ASTM C642 data, the owner rejected the deck. The contractor demolished and repoured. The test cost less than $500 per core. The replacement cost $2.3 million. Concrete is not a rock. It is a manufactured geology, and its performance depends entirely on the geometry of its emptiness. ASTM C642 is not glamorous. It involves no high-speed cameras or finite element models. It is just a scale, an oven, a boiling pot, and a calculator.