Voids In Hardened Concrete - Astm C642 Density Absorption

Note: Values >20% permeable voids generally indicate poor-quality concrete or a mix design error.

| Property | Typical Value | | :--- | :--- | | Dry Density | 125 – 155 lb/ft³ (2000 – 2480 kg/m³) | | Absorption | 4 – 8% | | Permeable Voids | 12 – 18% | astm c642 density absorption voids in hardened concrete

[ 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. The trouble is that water, chlorides, and sulfates

The trouble is that water, chlorides, and sulfates travel through these voids. Once they reach the reinforcing steel, the bridge dies from the inside. The contractor demolished and repoured

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.

The technician then weighs the sample submerged in water (using a wire suspending it from the scale). This gives the . Then, they remove it, gently blot it with a damp towel, and weigh it again in air. This is the Saturated Surface-Dry Mass (SSD) (B) . Step 3: The Arithmetic (Calculations) With three numbers—A (dry), B (SSD), and C (submerged)—the hidden geography of the concrete is revealed.

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.