ASTM C778 20/30 SAND

उत्पाद वर्णन

ASTM C778 specifies standard sand for use in the testing of hydraulic cements. The "20/30 sand" is one specific type of sand covered by this standard, often referred to as "tensile test sand."

Here's a description of ASTM C778 20/30 sand:

Key Characteristics:

 * Composition: It is typically a natural silica sand, meaning it's primarily composed of silicon dioxide (SiO2), often with a silica content of 98% or higher.

 * Grain Shape: The constituent grains are usually uncrushed and have a rounded or sub-rounded form. This is important for consistent packing and flow properties in testing.

 * Water Content: It typically has a very low water content, usually less than 0.1%.

 * Standardization: It must meet strict requirements for grading and be free from undesirable air-entraining characteristics.

Sieve Analysis (Grading) Requirements for 20/30 Sand (ASTM C778):

The "20/30" designation refers to its particle size distribution, specifically that it primarily passes through a No. 20 sieve and is retained on a No. 30 sieve. The exact percentages passing various sieves are critical for its standardization:

 * 1.18 mm (No. 16) sieve: 100% passing

 * 850 µm (No. 20) sieve: 85% to 100% passing

 * 600 µm (No. 30) sieve: 0% to 5% passing

Purpose and Use:

ASTM C778 20/30 sand is considered a "standard sand" because its consistent and controlled properties make it ideal for:

 * Testing Hydraulic Cements: It's primarily used as a reference material in various standard tests for hydraulic cements, such as:

   * ASTM C185: Standard Test Method for Air Content of Hydraulic Cement Mortar.

   * ASTM C190: (Discontinued standard, but 20/30 sand was used for tensile strength of hydraulic cement mortars).

   * ASTM C109: Standard Test Method for Compressive Strength of Hydraulic Cement Mortars (while "graded sand" is more common for this, 20/30 sand may also be referenced or used in specific contexts).

 * Ensuring Reproducibility: By using a standardized sand, laboratories can minimize variations in test results due to aggregate properties, thus ensuring the comparability and reproducibility of cement tests.

In essence, ASTM C778 20/30 sand is a precisely controlled, rounded silica sand designed to provide a consistent and reliable aggregate for critical tests of hydraulic cements.